/*------------------------------------------------------------------------- * * heapam.c * heap access method code * * Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * * IDENTIFICATION * src/backend/access/heap/heapam.c * * * INTERFACE ROUTINES * relation_open - open any relation by relation OID * relation_openrv - open any relation specified by a RangeVar * relation_close - close any relation * heap_open - open a heap relation by relation OID * heap_openrv - open a heap relation specified by a RangeVar * heap_close - (now just a macro for relation_close) * heap_beginscan - begin relation scan * heap_rescan - restart a relation scan * heap_endscan - end relation scan * heap_getnext - retrieve next tuple in scan * heap_fetch - retrieve tuple with given tid * heap_insert - insert tuple into a relation * heap_multi_insert - insert multiple tuples into a relation * heap_delete - delete a tuple from a relation * heap_update - replace a tuple in a relation with another tuple * heap_markpos - mark scan position * heap_restrpos - restore position to marked location * heap_sync - sync heap, for when no WAL has been written * * NOTES * This file contains the heap_ routines which implement * the POSTGRES heap access method used for all POSTGRES * relations. * *------------------------------------------------------------------------- */ #include "postgres.h" #include "access/heapam.h" #include "access/heapam_xlog.h" #include "access/hio.h" #include "access/multixact.h" #include "access/relscan.h" #include "access/sysattr.h" #include "access/transam.h" #include "access/tuptoaster.h" #include "access/valid.h" #include "access/visibilitymap.h" #include "access/xact.h" #include "access/xlogutils.h" #include "catalog/catalog.h" #include "catalog/namespace.h" #include "miscadmin.h" #include "pgstat.h" #include "storage/bufmgr.h" #include "storage/freespace.h" #include "storage/lmgr.h" #include "storage/predicate.h" #include "storage/procarray.h" #include "storage/smgr.h" #include "storage/standby.h" #include "utils/datum.h" #include "utils/inval.h" #include "utils/lsyscache.h" #include "utils/relcache.h" #include "utils/snapmgr.h" #include "utils/syscache.h" #include "utils/tqual.h" /* GUC variable */ bool synchronize_seqscans = true; static HeapScanDesc heap_beginscan_internal(Relation relation, Snapshot snapshot, int nkeys, ScanKey key, bool allow_strat, bool allow_sync, bool is_bitmapscan); static HeapTuple heap_prepare_insert(Relation relation, HeapTuple tup, TransactionId xid, CommandId cid, int options); static XLogRecPtr log_heap_update(Relation reln, Buffer oldbuf, Buffer newbuf, HeapTuple oldtup, HeapTuple newtup, bool all_visible_cleared, bool new_all_visible_cleared); static void HeapSatisfiesHOTandKeyUpdate(Relation relation, Bitmapset *hot_attrs, Bitmapset *key_attrs, bool *satisfies_hot, bool *satisfies_key, HeapTuple oldtup, HeapTuple newtup); static void compute_new_xmax_infomask(TransactionId xmax, uint16 old_infomask, uint16 old_infomask2, TransactionId add_to_xmax, LockTupleMode mode, bool is_update, TransactionId *result_xmax, uint16 *result_infomask, uint16 *result_infomask2); static HTSU_Result heap_lock_updated_tuple(Relation rel, HeapTuple tuple, ItemPointer ctid, TransactionId xid, LockTupleMode mode); static void GetMultiXactIdHintBits(MultiXactId multi, uint16 *new_infomask, uint16 *new_infomask2); static TransactionId MultiXactIdGetUpdateXid(TransactionId xmax, uint16 t_infomask); static void MultiXactIdWait(MultiXactId multi, MultiXactStatus status, int *remaining, uint16 infomask); static bool ConditionalMultiXactIdWait(MultiXactId multi, MultiXactStatus status, int *remaining, uint16 infomask); /* * Each tuple lock mode has a corresponding heavyweight lock, and one or two * corresponding MultiXactStatuses (one to merely lock tuples, another one to * update them). This table (and the macros below) helps us determine the * heavyweight lock mode and MultiXactStatus values to use for any particular * tuple lock strength. */ static const struct { LOCKMODE hwlock; MultiXactStatus lockstatus; MultiXactStatus updstatus; } tupleLockExtraInfo[MaxLockTupleMode + 1] = { { /* LockTupleKeyShare */ AccessShareLock, MultiXactStatusForKeyShare, -1 /* KeyShare does not allow updating tuples */ }, { /* LockTupleShare */ RowShareLock, MultiXactStatusForShare, -1 /* Share does not allow updating tuples */ }, { /* LockTupleNoKeyExclusive */ ExclusiveLock, MultiXactStatusForNoKeyUpdate, MultiXactStatusNoKeyUpdate }, { /* LockTupleExclusive */ AccessExclusiveLock, MultiXactStatusForUpdate, MultiXactStatusUpdate } }; /* Get the LOCKMODE for a given MultiXactStatus */ #define LOCKMODE_from_mxstatus(status) \ (tupleLockExtraInfo[TUPLOCK_from_mxstatus((status))].hwlock) /* * Acquire heavyweight locks on tuples, using a LockTupleMode strength value. * This is more readable than having every caller translate it to lock.h's * LOCKMODE. */ #define LockTupleTuplock(rel, tup, mode) \ LockTuple((rel), (tup), tupleLockExtraInfo[mode].hwlock) #define UnlockTupleTuplock(rel, tup, mode) \ UnlockTuple((rel), (tup), tupleLockExtraInfo[mode].hwlock) #define ConditionalLockTupleTuplock(rel, tup, mode) \ ConditionalLockTuple((rel), (tup), tupleLockExtraInfo[mode].hwlock) /* * This table maps tuple lock strength values for each particular * MultiXactStatus value. */ static const int MultiXactStatusLock[MaxMultiXactStatus + 1] = { LockTupleKeyShare, /* ForKeyShare */ LockTupleShare, /* ForShare */ LockTupleNoKeyExclusive, /* ForNoKeyUpdate */ LockTupleExclusive, /* ForUpdate */ LockTupleNoKeyExclusive, /* NoKeyUpdate */ LockTupleExclusive /* Update */ }; /* Get the LockTupleMode for a given MultiXactStatus */ #define TUPLOCK_from_mxstatus(status) \ (MultiXactStatusLock[(status)]) /* Get the is_update bit for a given MultiXactStatus */ #define ISUPDATE_from_mxstatus(status) \ ((status) > MultiXactStatusForUpdate) /* ---------------------------------------------------------------- * heap support routines * ---------------------------------------------------------------- */ /* ---------------- * initscan - scan code common to heap_beginscan and heap_rescan * ---------------- */ static void initscan(HeapScanDesc scan, ScanKey key, bool is_rescan) { bool allow_strat; bool allow_sync; /* * Determine the number of blocks we have to scan. * * It is sufficient to do this once at scan start, since any tuples added * while the scan is in progress will be invisible to my snapshot anyway. * (That is not true when using a non-MVCC snapshot. However, we couldn't * guarantee to return tuples added after scan start anyway, since they * might go into pages we already scanned. To guarantee consistent * results for a non-MVCC snapshot, the caller must hold some higher-level * lock that ensures the interesting tuple(s) won't change.) */ scan->rs_nblocks = RelationGetNumberOfBlocks(scan->rs_rd); /* * If the table is large relative to NBuffers, use a bulk-read access * strategy and enable synchronized scanning (see syncscan.c). Although * the thresholds for these features could be different, we make them the * same so that there are only two behaviors to tune rather than four. * (However, some callers need to be able to disable one or both of these * behaviors, independently of the size of the table; also there is a GUC * variable that can disable synchronized scanning.) * * During a rescan, don't make a new strategy object if we don't have to. */ if (!RelationUsesLocalBuffers(scan->rs_rd) && scan->rs_nblocks > NBuffers / 4) { allow_strat = scan->rs_allow_strat; allow_sync = scan->rs_allow_sync; } else allow_strat = allow_sync = false; if (allow_strat) { if (scan->rs_strategy == NULL) scan->rs_strategy = GetAccessStrategy(BAS_BULKREAD); } else { if (scan->rs_strategy != NULL) FreeAccessStrategy(scan->rs_strategy); scan->rs_strategy = NULL; } if (is_rescan) { /* * If rescan, keep the previous startblock setting so that rewinding a * cursor doesn't generate surprising results. Reset the syncscan * setting, though. */ scan->rs_syncscan = (allow_sync && synchronize_seqscans); } else if (allow_sync && synchronize_seqscans) { scan->rs_syncscan = true; scan->rs_startblock = ss_get_location(scan->rs_rd, scan->rs_nblocks); } else { scan->rs_syncscan = false; scan->rs_startblock = 0; } scan->rs_inited = false; scan->rs_ctup.t_data = NULL; ItemPointerSetInvalid(&scan->rs_ctup.t_self); scan->rs_cbuf = InvalidBuffer; scan->rs_cblock = InvalidBlockNumber; /* we don't have a marked position... */ ItemPointerSetInvalid(&(scan->rs_mctid)); /* page-at-a-time fields are always invalid when not rs_inited */ /* * copy the scan key, if appropriate */ if (key != NULL) memcpy(scan->rs_key, key, scan->rs_nkeys * sizeof(ScanKeyData)); /* * Currently, we don't have a stats counter for bitmap heap scans (but the * underlying bitmap index scans will be counted). */ if (!scan->rs_bitmapscan) pgstat_count_heap_scan(scan->rs_rd); } /* * heapgetpage - subroutine for heapgettup() * * This routine reads and pins the specified page of the relation. * In page-at-a-time mode it performs additional work, namely determining * which tuples on the page are visible. */ static void heapgetpage(HeapScanDesc scan, BlockNumber page) { Buffer buffer; Snapshot snapshot; Page dp; int lines; int ntup; OffsetNumber lineoff; ItemId lpp; bool all_visible; Assert(page < scan->rs_nblocks); /* release previous scan buffer, if any */ if (BufferIsValid(scan->rs_cbuf)) { ReleaseBuffer(scan->rs_cbuf); scan->rs_cbuf = InvalidBuffer; } /* * Be sure to check for interrupts at least once per page. Checks at * higher code levels won't be able to stop a seqscan that encounters many * pages' worth of consecutive dead tuples. */ CHECK_FOR_INTERRUPTS(); /* read page using selected strategy */ scan->rs_cbuf = ReadBufferExtended(scan->rs_rd, MAIN_FORKNUM, page, RBM_NORMAL, scan->rs_strategy); scan->rs_cblock = page; if (!scan->rs_pageatatime) return; buffer = scan->rs_cbuf; snapshot = scan->rs_snapshot; /* * Prune and repair fragmentation for the whole page, if possible. */ Assert(TransactionIdIsValid(RecentGlobalXmin)); heap_page_prune_opt(scan->rs_rd, buffer, RecentGlobalXmin); /* * We must hold share lock on the buffer content while examining tuple * visibility. Afterwards, however, the tuples we have found to be * visible are guaranteed good as long as we hold the buffer pin. */ LockBuffer(buffer, BUFFER_LOCK_SHARE); dp = (Page) BufferGetPage(buffer); lines = PageGetMaxOffsetNumber(dp); ntup = 0; /* * If the all-visible flag indicates that all tuples on the page are * visible to everyone, we can skip the per-tuple visibility tests. * * Note: In hot standby, a tuple that's already visible to all * transactions in the master might still be invisible to a read-only * transaction in the standby. We partly handle this problem by tracking * the minimum xmin of visible tuples as the cut-off XID while marking a * page all-visible on master and WAL log that along with the visibility * map SET operation. In hot standby, we wait for (or abort) all * transactions that can potentially may not see one or more tuples on the * page. That's how index-only scans work fine in hot standby. A crucial * difference between index-only scans and heap scans is that the * index-only scan completely relies on the visibility map where as heap * scan looks at the page-level PD_ALL_VISIBLE flag. We are not sure if * the page-level flag can be trusted in the same way, because it might * get propagated somehow without being explicitly WAL-logged, e.g. via a * full page write. Until we can prove that beyond doubt, let's check each * tuple for visibility the hard way. */ all_visible = PageIsAllVisible(dp) && !snapshot->takenDuringRecovery; for (lineoff = FirstOffsetNumber, lpp = PageGetItemId(dp, lineoff); lineoff <= lines; lineoff++, lpp++) { if (ItemIdIsNormal(lpp)) { HeapTupleData loctup; bool valid; loctup.t_data = (HeapTupleHeader) PageGetItem((Page) dp, lpp); loctup.t_len = ItemIdGetLength(lpp); ItemPointerSet(&(loctup.t_self), page, lineoff); if (all_visible) valid = true; else valid = HeapTupleSatisfiesVisibility(&loctup, snapshot, buffer); CheckForSerializableConflictOut(valid, scan->rs_rd, &loctup, buffer, snapshot); if (valid) scan->rs_vistuples[ntup++] = lineoff; } } LockBuffer(buffer, BUFFER_LOCK_UNLOCK); Assert(ntup <= MaxHeapTuplesPerPage); scan->rs_ntuples = ntup; } /* ---------------- * heapgettup - fetch next heap tuple * * Initialize the scan if not already done; then advance to the next * tuple as indicated by "dir"; return the next tuple in scan->rs_ctup, * or set scan->rs_ctup.t_data = NULL if no more tuples. * * dir == NoMovementScanDirection means "re-fetch the tuple indicated * by scan->rs_ctup". * * Note: the reason nkeys/key are passed separately, even though they are * kept in the scan descriptor, is that the caller may not want us to check * the scankeys. * * Note: when we fall off the end of the scan in either direction, we * reset rs_inited. This means that a further request with the same * scan direction will restart the scan, which is a bit odd, but a * request with the opposite scan direction will start a fresh scan * in the proper direction. The latter is required behavior for cursors, * while the former case is generally undefined behavior in Postgres * so we don't care too much. * ---------------- */ static void heapgettup(HeapScanDesc scan, ScanDirection dir, int nkeys, ScanKey key) { HeapTuple tuple = &(scan->rs_ctup); Snapshot snapshot = scan->rs_snapshot; bool backward = ScanDirectionIsBackward(dir); BlockNumber page; bool finished; Page dp; int lines; OffsetNumber lineoff; int linesleft; ItemId lpp; /* * calculate next starting lineoff, given scan direction */ if (ScanDirectionIsForward(dir)) { if (!scan->rs_inited) { /* * return null immediately if relation is empty */ if (scan->rs_nblocks == 0) { Assert(!BufferIsValid(scan->rs_cbuf)); tuple->t_data = NULL; return; } page = scan->rs_startblock; /* first page */ heapgetpage(scan, page); lineoff = FirstOffsetNumber; /* first offnum */ scan->rs_inited = true; } else { /* continue from previously returned page/tuple */ page = scan->rs_cblock; /* current page */ lineoff = /* next offnum */ OffsetNumberNext(ItemPointerGetOffsetNumber(&(tuple->t_self))); } LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE); dp = (Page) BufferGetPage(scan->rs_cbuf); lines = PageGetMaxOffsetNumber(dp); /* page and lineoff now reference the physically next tid */ linesleft = lines - lineoff + 1; } else if (backward) { if (!scan->rs_inited) { /* * return null immediately if relation is empty */ if (scan->rs_nblocks == 0) { Assert(!BufferIsValid(scan->rs_cbuf)); tuple->t_data = NULL; return; } /* * Disable reporting to syncscan logic in a backwards scan; it's * not very likely anyone else is doing the same thing at the same * time, and much more likely that we'll just bollix things for * forward scanners. */ scan->rs_syncscan = false; /* start from last page of the scan */ if (scan->rs_startblock > 0) page = scan->rs_startblock - 1; else page = scan->rs_nblocks - 1; heapgetpage(scan, page); } else { /* continue from previously returned page/tuple */ page = scan->rs_cblock; /* current page */ } LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE); dp = (Page) BufferGetPage(scan->rs_cbuf); lines = PageGetMaxOffsetNumber(dp); if (!scan->rs_inited) { lineoff = lines; /* final offnum */ scan->rs_inited = true; } else { lineoff = /* previous offnum */ OffsetNumberPrev(ItemPointerGetOffsetNumber(&(tuple->t_self))); } /* page and lineoff now reference the physically previous tid */ linesleft = lineoff; } else { /* * ``no movement'' scan direction: refetch prior tuple */ if (!scan->rs_inited) { Assert(!BufferIsValid(scan->rs_cbuf)); tuple->t_data = NULL; return; } page = ItemPointerGetBlockNumber(&(tuple->t_self)); if (page != scan->rs_cblock) heapgetpage(scan, page); /* Since the tuple was previously fetched, needn't lock page here */ dp = (Page) BufferGetPage(scan->rs_cbuf); lineoff = ItemPointerGetOffsetNumber(&(tuple->t_self)); lpp = PageGetItemId(dp, lineoff); Assert(ItemIdIsNormal(lpp)); tuple->t_data = (HeapTupleHeader) PageGetItem((Page) dp, lpp); tuple->t_len = ItemIdGetLength(lpp); return; } /* * advance the scan until we find a qualifying tuple or run out of stuff * to scan */ lpp = PageGetItemId(dp, lineoff); for (;;) { while (linesleft > 0) { if (ItemIdIsNormal(lpp)) { bool valid; tuple->t_data = (HeapTupleHeader) PageGetItem((Page) dp, lpp); tuple->t_len = ItemIdGetLength(lpp); ItemPointerSet(&(tuple->t_self), page, lineoff); /* * if current tuple qualifies, return it. */ valid = HeapTupleSatisfiesVisibility(tuple, snapshot, scan->rs_cbuf); CheckForSerializableConflictOut(valid, scan->rs_rd, tuple, scan->rs_cbuf, snapshot); if (valid && key != NULL) HeapKeyTest(tuple, RelationGetDescr(scan->rs_rd), nkeys, key, valid); if (valid) { LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK); return; } } /* * otherwise move to the next item on the page */ --linesleft; if (backward) { --lpp; /* move back in this page's ItemId array */ --lineoff; } else { ++lpp; /* move forward in this page's ItemId array */ ++lineoff; } } /* * if we get here, it means we've exhausted the items on this page and * it's time to move to the next. */ LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK); /* * advance to next/prior page and detect end of scan */ if (backward) { finished = (page == scan->rs_startblock); if (page == 0) page = scan->rs_nblocks; page--; } else { page++; if (page >= scan->rs_nblocks) page = 0; finished = (page == scan->rs_startblock); /* * Report our new scan position for synchronization purposes. We * don't do that when moving backwards, however. That would just * mess up any other forward-moving scanners. * * Note: we do this before checking for end of scan so that the * final state of the position hint is back at the start of the * rel. That's not strictly necessary, but otherwise when you run * the same query multiple times the starting position would shift * a little bit backwards on every invocation, which is confusing. * We don't guarantee any specific ordering in general, though. */ if (scan->rs_syncscan) ss_report_location(scan->rs_rd, page); } /* * return NULL if we've exhausted all the pages */ if (finished) { if (BufferIsValid(scan->rs_cbuf)) ReleaseBuffer(scan->rs_cbuf); scan->rs_cbuf = InvalidBuffer; scan->rs_cblock = InvalidBlockNumber; tuple->t_data = NULL; scan->rs_inited = false; return; } heapgetpage(scan, page); LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE); dp = (Page) BufferGetPage(scan->rs_cbuf); lines = PageGetMaxOffsetNumber((Page) dp); linesleft = lines; if (backward) { lineoff = lines; lpp = PageGetItemId(dp, lines); } else { lineoff = FirstOffsetNumber; lpp = PageGetItemId(dp, FirstOffsetNumber); } } } /* ---------------- * heapgettup_pagemode - fetch next heap tuple in page-at-a-time mode * * Same API as heapgettup, but used in page-at-a-time mode * * The internal logic is much the same as heapgettup's too, but there are some * differences: we do not take the buffer content lock (that only needs to * happen inside heapgetpage), and we iterate through just the tuples listed * in rs_vistuples[] rather than all tuples on the page. Notice that * lineindex is 0-based, where the corresponding loop variable lineoff in * heapgettup is 1-based. * ---------------- */ static void heapgettup_pagemode(HeapScanDesc scan, ScanDirection dir, int nkeys, ScanKey key) { HeapTuple tuple = &(scan->rs_ctup); bool backward = ScanDirectionIsBackward(dir); BlockNumber page; bool finished; Page dp; int lines; int lineindex; OffsetNumber lineoff; int linesleft; ItemId lpp; /* * calculate next starting lineindex, given scan direction */ if (ScanDirectionIsForward(dir)) { if (!scan->rs_inited) { /* * return null immediately if relation is empty */ if (scan->rs_nblocks == 0) { Assert(!BufferIsValid(scan->rs_cbuf)); tuple->t_data = NULL; return; } page = scan->rs_startblock; /* first page */ heapgetpage(scan, page); lineindex = 0; scan->rs_inited = true; } else { /* continue from previously returned page/tuple */ page = scan->rs_cblock; /* current page */ lineindex = scan->rs_cindex + 1; } dp = (Page) BufferGetPage(scan->rs_cbuf); lines = scan->rs_ntuples; /* page and lineindex now reference the next visible tid */ linesleft = lines - lineindex; } else if (backward) { if (!scan->rs_inited) { /* * return null immediately if relation is empty */ if (scan->rs_nblocks == 0) { Assert(!BufferIsValid(scan->rs_cbuf)); tuple->t_data = NULL; return; } /* * Disable reporting to syncscan logic in a backwards scan; it's * not very likely anyone else is doing the same thing at the same * time, and much more likely that we'll just bollix things for * forward scanners. */ scan->rs_syncscan = false; /* start from last page of the scan */ if (scan->rs_startblock > 0) page = scan->rs_startblock - 1; else page = scan->rs_nblocks - 1; heapgetpage(scan, page); } else { /* continue from previously returned page/tuple */ page = scan->rs_cblock; /* current page */ } dp = (Page) BufferGetPage(scan->rs_cbuf); lines = scan->rs_ntuples; if (!scan->rs_inited) { lineindex = lines - 1; scan->rs_inited = true; } else { lineindex = scan->rs_cindex - 1; } /* page and lineindex now reference the previous visible tid */ linesleft = lineindex + 1; } else { /* * ``no movement'' scan direction: refetch prior tuple */ if (!scan->rs_inited) { Assert(!BufferIsValid(scan->rs_cbuf)); tuple->t_data = NULL; return; } page = ItemPointerGetBlockNumber(&(tuple->t_self)); if (page != scan->rs_cblock) heapgetpage(scan, page); /* Since the tuple was previously fetched, needn't lock page here */ dp = (Page) BufferGetPage(scan->rs_cbuf); lineoff = ItemPointerGetOffsetNumber(&(tuple->t_self)); lpp = PageGetItemId(dp, lineoff); Assert(ItemIdIsNormal(lpp)); tuple->t_data = (HeapTupleHeader) PageGetItem((Page) dp, lpp); tuple->t_len = ItemIdGetLength(lpp); /* check that rs_cindex is in sync */ Assert(scan->rs_cindex < scan->rs_ntuples); Assert(lineoff == scan->rs_vistuples[scan->rs_cindex]); return; } /* * advance the scan until we find a qualifying tuple or run out of stuff * to scan */ for (;;) { while (linesleft > 0) { lineoff = scan->rs_vistuples[lineindex]; lpp = PageGetItemId(dp, lineoff); Assert(ItemIdIsNormal(lpp)); tuple->t_data = (HeapTupleHeader) PageGetItem((Page) dp, lpp); tuple->t_len = ItemIdGetLength(lpp); ItemPointerSet(&(tuple->t_self), page, lineoff); /* * if current tuple qualifies, return it. */ if (key != NULL) { bool valid; HeapKeyTest(tuple, RelationGetDescr(scan->rs_rd), nkeys, key, valid); if (valid) { scan->rs_cindex = lineindex; return; } } else { scan->rs_cindex = lineindex; return; } /* * otherwise move to the next item on the page */ --linesleft; if (backward) --lineindex; else ++lineindex; } /* * if we get here, it means we've exhausted the items on this page and * it's time to move to the next. */ if (backward) { finished = (page == scan->rs_startblock); if (page == 0) page = scan->rs_nblocks; page--; } else { page++; if (page >= scan->rs_nblocks) page = 0; finished = (page == scan->rs_startblock); /* * Report our new scan position for synchronization purposes. We * don't do that when moving backwards, however. That would just * mess up any other forward-moving scanners. * * Note: we do this before checking for end of scan so that the * final state of the position hint is back at the start of the * rel. That's not strictly necessary, but otherwise when you run * the same query multiple times the starting position would shift * a little bit backwards on every invocation, which is confusing. * We don't guarantee any specific ordering in general, though. */ if (scan->rs_syncscan) ss_report_location(scan->rs_rd, page); } /* * return NULL if we've exhausted all the pages */ if (finished) { if (BufferIsValid(scan->rs_cbuf)) ReleaseBuffer(scan->rs_cbuf); scan->rs_cbuf = InvalidBuffer; scan->rs_cblock = InvalidBlockNumber; tuple->t_data = NULL; scan->rs_inited = false; return; } heapgetpage(scan, page); dp = (Page) BufferGetPage(scan->rs_cbuf); lines = scan->rs_ntuples; linesleft = lines; if (backward) lineindex = lines - 1; else lineindex = 0; } } #if defined(DISABLE_COMPLEX_MACRO) /* * This is formatted so oddly so that the correspondence to the macro * definition in access/htup.h is maintained. */ Datum fastgetattr(HeapTuple tup, int attnum, TupleDesc tupleDesc, bool *isnull) { return ( (attnum) > 0 ? ( (*(isnull) = false), HeapTupleNoNulls(tup) ? ( (tupleDesc)->attrs[(attnum) - 1]->attcacheoff >= 0 ? ( fetchatt((tupleDesc)->attrs[(attnum) - 1], (char *) (tup)->t_data + (tup)->t_data->t_hoff + (tupleDesc)->attrs[(attnum) - 1]->attcacheoff) ) : nocachegetattr((tup), (attnum), (tupleDesc)) ) : ( att_isnull((attnum) - 1, (tup)->t_data->t_bits) ? ( (*(isnull) = true), (Datum) NULL ) : ( nocachegetattr((tup), (attnum), (tupleDesc)) ) ) ) : ( (Datum) NULL ) ); } #endif /* defined(DISABLE_COMPLEX_MACRO) */ /* ---------------------------------------------------------------- * heap access method interface * ---------------------------------------------------------------- */ /* ---------------- * relation_open - open any relation by relation OID * * If lockmode is not "NoLock", the specified kind of lock is * obtained on the relation. (Generally, NoLock should only be * used if the caller knows it has some appropriate lock on the * relation already.) * * An error is raised if the relation does not exist. * * NB: a "relation" is anything with a pg_class entry. The caller is * expected to check whether the relkind is something it can handle. * ---------------- */ Relation relation_open(Oid relationId, LOCKMODE lockmode) { Relation r; Assert(lockmode >= NoLock && lockmode < MAX_LOCKMODES); /* Get the lock before trying to open the relcache entry */ if (lockmode != NoLock) LockRelationOid(relationId, lockmode); /* The relcache does all the real work... */ r = RelationIdGetRelation(relationId); if (!RelationIsValid(r)) elog(ERROR, "could not open relation with OID %u", relationId); /* Make note that we've accessed a temporary relation */ if (RelationUsesLocalBuffers(r)) MyXactAccessedTempRel = true; pgstat_initstats(r); return r; } /* ---------------- * try_relation_open - open any relation by relation OID * * Same as relation_open, except return NULL instead of failing * if the relation does not exist. * ---------------- */ Relation try_relation_open(Oid relationId, LOCKMODE lockmode) { Relation r; Assert(lockmode >= NoLock && lockmode < MAX_LOCKMODES); /* Get the lock first */ if (lockmode != NoLock) LockRelationOid(relationId, lockmode); /* * Now that we have the lock, probe to see if the relation really exists * or not. */ if (!SearchSysCacheExists1(RELOID, ObjectIdGetDatum(relationId))) { /* Release useless lock */ if (lockmode != NoLock) UnlockRelationOid(relationId, lockmode); return NULL; } /* Should be safe to do a relcache load */ r = RelationIdGetRelation(relationId); if (!RelationIsValid(r)) elog(ERROR, "could not open relation with OID %u", relationId); /* Make note that we've accessed a temporary relation */ if (RelationUsesLocalBuffers(r)) MyXactAccessedTempRel = true; pgstat_initstats(r); return r; } /* ---------------- * relation_openrv - open any relation specified by a RangeVar * * Same as relation_open, but the relation is specified by a RangeVar. * ---------------- */ Relation relation_openrv(const RangeVar *relation, LOCKMODE lockmode) { Oid relOid; /* * Check for shared-cache-inval messages before trying to open the * relation. This is needed even if we already hold a lock on the * relation, because GRANT/REVOKE are executed without taking any lock on * the target relation, and we want to be sure we see current ACL * information. We can skip this if asked for NoLock, on the assumption * that such a call is not the first one in the current command, and so we * should be reasonably up-to-date already. (XXX this all could stand to * be redesigned, but for the moment we'll keep doing this like it's been * done historically.) */ if (lockmode != NoLock) AcceptInvalidationMessages(); /* Look up and lock the appropriate relation using namespace search */ relOid = RangeVarGetRelid(relation, lockmode, false); /* Let relation_open do the rest */ return relation_open(relOid, NoLock); } /* ---------------- * relation_openrv_extended - open any relation specified by a RangeVar * * Same as relation_openrv, but with an additional missing_ok argument * allowing a NULL return rather than an error if the relation is not * found. (Note that some other causes, such as permissions problems, * will still result in an ereport.) * ---------------- */ Relation relation_openrv_extended(const RangeVar *relation, LOCKMODE lockmode, bool missing_ok) { Oid relOid; /* * Check for shared-cache-inval messages before trying to open the * relation. See comments in relation_openrv(). */ if (lockmode != NoLock) AcceptInvalidationMessages(); /* Look up and lock the appropriate relation using namespace search */ relOid = RangeVarGetRelid(relation, lockmode, missing_ok); /* Return NULL on not-found */ if (!OidIsValid(relOid)) return NULL; /* Let relation_open do the rest */ return relation_open(relOid, NoLock); } /* ---------------- * relation_close - close any relation * * If lockmode is not "NoLock", we then release the specified lock. * * Note that it is often sensible to hold a lock beyond relation_close; * in that case, the lock is released automatically at xact end. * ---------------- */ void relation_close(Relation relation, LOCKMODE lockmode) { LockRelId relid = relation->rd_lockInfo.lockRelId; Assert(lockmode >= NoLock && lockmode < MAX_LOCKMODES); /* The relcache does the real work... */ RelationClose(relation); if (lockmode != NoLock) UnlockRelationId(&relid, lockmode); } /* ---------------- * heap_open - open a heap relation by relation OID * * This is essentially relation_open plus check that the relation * is not an index nor a composite type. (The caller should also * check that it's not a view or foreign table before assuming it has * storage.) * ---------------- */ Relation heap_open(Oid relationId, LOCKMODE lockmode) { Relation r; r = relation_open(relationId, lockmode); if (r->rd_rel->relkind == RELKIND_INDEX) ereport(ERROR, (errcode(ERRCODE_WRONG_OBJECT_TYPE), errmsg("\"%s\" is an index", RelationGetRelationName(r)))); else if (r->rd_rel->relkind == RELKIND_COMPOSITE_TYPE) ereport(ERROR, (errcode(ERRCODE_WRONG_OBJECT_TYPE), errmsg("\"%s\" is a composite type", RelationGetRelationName(r)))); return r; } /* ---------------- * heap_openrv - open a heap relation specified * by a RangeVar node * * As above, but relation is specified by a RangeVar. * ---------------- */ Relation heap_openrv(const RangeVar *relation, LOCKMODE lockmode) { Relation r; r = relation_openrv(relation, lockmode); if (r->rd_rel->relkind == RELKIND_INDEX) ereport(ERROR, (errcode(ERRCODE_WRONG_OBJECT_TYPE), errmsg("\"%s\" is an index", RelationGetRelationName(r)))); else if (r->rd_rel->relkind == RELKIND_COMPOSITE_TYPE) ereport(ERROR, (errcode(ERRCODE_WRONG_OBJECT_TYPE), errmsg("\"%s\" is a composite type", RelationGetRelationName(r)))); return r; } /* ---------------- * heap_openrv_extended - open a heap relation specified * by a RangeVar node * * As above, but optionally return NULL instead of failing for * relation-not-found. * ---------------- */ Relation heap_openrv_extended(const RangeVar *relation, LOCKMODE lockmode, bool missing_ok) { Relation r; r = relation_openrv_extended(relation, lockmode, missing_ok); if (r) { if (r->rd_rel->relkind == RELKIND_INDEX) ereport(ERROR, (errcode(ERRCODE_WRONG_OBJECT_TYPE), errmsg("\"%s\" is an index", RelationGetRelationName(r)))); else if (r->rd_rel->relkind == RELKIND_COMPOSITE_TYPE) ereport(ERROR, (errcode(ERRCODE_WRONG_OBJECT_TYPE), errmsg("\"%s\" is a composite type", RelationGetRelationName(r)))); } return r; } /* ---------------- * heap_beginscan - begin relation scan * * heap_beginscan_strat offers an extended API that lets the caller control * whether a nondefault buffer access strategy can be used, and whether * syncscan can be chosen (possibly resulting in the scan not starting from * block zero). Both of these default to TRUE with plain heap_beginscan. * * heap_beginscan_bm is an alternative entry point for setting up a * HeapScanDesc for a bitmap heap scan. Although that scan technology is * really quite unlike a standard seqscan, there is just enough commonality * to make it worth using the same data structure. * ---------------- */ HeapScanDesc heap_beginscan(Relation relation, Snapshot snapshot, int nkeys, ScanKey key) { return heap_beginscan_internal(relation, snapshot, nkeys, key, true, true, false); } HeapScanDesc heap_beginscan_strat(Relation relation, Snapshot snapshot, int nkeys, ScanKey key, bool allow_strat, bool allow_sync) { return heap_beginscan_internal(relation, snapshot, nkeys, key, allow_strat, allow_sync, false); } HeapScanDesc heap_beginscan_bm(Relation relation, Snapshot snapshot, int nkeys, ScanKey key) { return heap_beginscan_internal(relation, snapshot, nkeys, key, false, false, true); } static HeapScanDesc heap_beginscan_internal(Relation relation, Snapshot snapshot, int nkeys, ScanKey key, bool allow_strat, bool allow_sync, bool is_bitmapscan) { HeapScanDesc scan; /* * increment relation ref count while scanning relation * * This is just to make really sure the relcache entry won't go away while * the scan has a pointer to it. Caller should be holding the rel open * anyway, so this is redundant in all normal scenarios... */ RelationIncrementReferenceCount(relation); /* * allocate and initialize scan descriptor */ scan = (HeapScanDesc) palloc(sizeof(HeapScanDescData)); scan->rs_rd = relation; scan->rs_snapshot = snapshot; scan->rs_nkeys = nkeys; scan->rs_bitmapscan = is_bitmapscan; scan->rs_strategy = NULL; /* set in initscan */ scan->rs_allow_strat = allow_strat; scan->rs_allow_sync = allow_sync; /* * we can use page-at-a-time mode if it's an MVCC-safe snapshot */ scan->rs_pageatatime = IsMVCCSnapshot(snapshot); /* * For a seqscan in a serializable transaction, acquire a predicate lock * on the entire relation. This is required not only to lock all the * matching tuples, but also to conflict with new insertions into the * table. In an indexscan, we take page locks on the index pages covering * the range specified in the scan qual, but in a heap scan there is * nothing more fine-grained to lock. A bitmap scan is a different story, * there we have already scanned the index and locked the index pages * covering the predicate. But in that case we still have to lock any * matching heap tuples. */ if (!is_bitmapscan) PredicateLockRelation(relation, snapshot); /* we only need to set this up once */ scan->rs_ctup.t_tableOid = RelationGetRelid(relation); /* * we do this here instead of in initscan() because heap_rescan also calls * initscan() and we don't want to allocate memory again */ if (nkeys > 0) scan->rs_key = (ScanKey) palloc(sizeof(ScanKeyData) * nkeys); else scan->rs_key = NULL; initscan(scan, key, false); return scan; } /* ---------------- * heap_rescan - restart a relation scan * ---------------- */ void heap_rescan(HeapScanDesc scan, ScanKey key) { /* * unpin scan buffers */ if (BufferIsValid(scan->rs_cbuf)) ReleaseBuffer(scan->rs_cbuf); /* * reinitialize scan descriptor */ initscan(scan, key, true); } /* ---------------- * heap_endscan - end relation scan * * See how to integrate with index scans. * Check handling if reldesc caching. * ---------------- */ void heap_endscan(HeapScanDesc scan) { /* Note: no locking manipulations needed */ /* * unpin scan buffers */ if (BufferIsValid(scan->rs_cbuf)) ReleaseBuffer(scan->rs_cbuf); /* * decrement relation reference count and free scan descriptor storage */ RelationDecrementReferenceCount(scan->rs_rd); if (scan->rs_key) pfree(scan->rs_key); if (scan->rs_strategy != NULL) FreeAccessStrategy(scan->rs_strategy); pfree(scan); } /* ---------------- * heap_getnext - retrieve next tuple in scan * * Fix to work with index relations. * We don't return the buffer anymore, but you can get it from the * returned HeapTuple. * ---------------- */ #ifdef HEAPDEBUGALL #define HEAPDEBUG_1 \ elog(DEBUG2, "heap_getnext([%s,nkeys=%d],dir=%d) called", \ RelationGetRelationName(scan->rs_rd), scan->rs_nkeys, (int) direction) #define HEAPDEBUG_2 \ elog(DEBUG2, "heap_getnext returning EOS") #define HEAPDEBUG_3 \ elog(DEBUG2, "heap_getnext returning tuple") #else #define HEAPDEBUG_1 #define HEAPDEBUG_2 #define HEAPDEBUG_3 #endif /* !defined(HEAPDEBUGALL) */ HeapTuple heap_getnext(HeapScanDesc scan, ScanDirection direction) { /* Note: no locking manipulations needed */ HEAPDEBUG_1; /* heap_getnext( info ) */ if (scan->rs_pageatatime) heapgettup_pagemode(scan, direction, scan->rs_nkeys, scan->rs_key); else heapgettup(scan, direction, scan->rs_nkeys, scan->rs_key); if (scan->rs_ctup.t_data == NULL) { HEAPDEBUG_2; /* heap_getnext returning EOS */ return NULL; } /* * if we get here it means we have a new current scan tuple, so point to * the proper return buffer and return the tuple. */ HEAPDEBUG_3; /* heap_getnext returning tuple */ pgstat_count_heap_getnext(scan->rs_rd); return &(scan->rs_ctup); } /* * heap_fetch - retrieve tuple with given tid * * On entry, tuple->t_self is the TID to fetch. We pin the buffer holding * the tuple, fill in the remaining fields of *tuple, and check the tuple * against the specified snapshot. * * If successful (tuple found and passes snapshot time qual), then *userbuf * is set to the buffer holding the tuple and TRUE is returned. The caller * must unpin the buffer when done with the tuple. * * If the tuple is not found (ie, item number references a deleted slot), * then tuple->t_data is set to NULL and FALSE is returned. * * If the tuple is found but fails the time qual check, then FALSE is returned * but tuple->t_data is left pointing to the tuple. * * keep_buf determines what is done with the buffer in the FALSE-result cases. * When the caller specifies keep_buf = true, we retain the pin on the buffer * and return it in *userbuf (so the caller must eventually unpin it); when * keep_buf = false, the pin is released and *userbuf is set to InvalidBuffer. * * stats_relation is the relation to charge the heap_fetch operation against * for statistical purposes. (This could be the heap rel itself, an * associated index, or NULL to not count the fetch at all.) * * heap_fetch does not follow HOT chains: only the exact TID requested will * be fetched. * * It is somewhat inconsistent that we ereport() on invalid block number but * return false on invalid item number. There are a couple of reasons though. * One is that the caller can relatively easily check the block number for * validity, but cannot check the item number without reading the page * himself. Another is that when we are following a t_ctid link, we can be * reasonably confident that the page number is valid (since VACUUM shouldn't * truncate off the destination page without having killed the referencing * tuple first), but the item number might well not be good. */ bool heap_fetch(Relation relation, Snapshot snapshot, HeapTuple tuple, Buffer *userbuf, bool keep_buf, Relation stats_relation) { ItemPointer tid = &(tuple->t_self); ItemId lp; Buffer buffer; Page page; OffsetNumber offnum; bool valid; /* * Fetch and pin the appropriate page of the relation. */ buffer = ReadBuffer(relation, ItemPointerGetBlockNumber(tid)); /* * Need share lock on buffer to examine tuple commit status. */ LockBuffer(buffer, BUFFER_LOCK_SHARE); page = BufferGetPage(buffer); /* * We'd better check for out-of-range offnum in case of VACUUM since the * TID was obtained. */ offnum = ItemPointerGetOffsetNumber(tid); if (offnum < FirstOffsetNumber || offnum > PageGetMaxOffsetNumber(page)) { LockBuffer(buffer, BUFFER_LOCK_UNLOCK); if (keep_buf) *userbuf = buffer; else { ReleaseBuffer(buffer); *userbuf = InvalidBuffer; } tuple->t_data = NULL; return false; } /* * get the item line pointer corresponding to the requested tid */ lp = PageGetItemId(page, offnum); /* * Must check for deleted tuple. */ if (!ItemIdIsNormal(lp)) { LockBuffer(buffer, BUFFER_LOCK_UNLOCK); if (keep_buf) *userbuf = buffer; else { ReleaseBuffer(buffer); *userbuf = InvalidBuffer; } tuple->t_data = NULL; return false; } /* * fill in *tuple fields */ tuple->t_data = (HeapTupleHeader) PageGetItem(page, lp); tuple->t_len = ItemIdGetLength(lp); tuple->t_tableOid = RelationGetRelid(relation); /* * check time qualification of tuple, then release lock */ valid = HeapTupleSatisfiesVisibility(tuple, snapshot, buffer); if (valid) PredicateLockTuple(relation, tuple, snapshot); CheckForSerializableConflictOut(valid, relation, tuple, buffer, snapshot); LockBuffer(buffer, BUFFER_LOCK_UNLOCK); if (valid) { /* * All checks passed, so return the tuple as valid. Caller is now * responsible for releasing the buffer. */ *userbuf = buffer; /* Count the successful fetch against appropriate rel, if any */ if (stats_relation != NULL) pgstat_count_heap_fetch(stats_relation); return true; } /* Tuple failed time qual, but maybe caller wants to see it anyway. */ if (keep_buf) *userbuf = buffer; else { ReleaseBuffer(buffer); *userbuf = InvalidBuffer; } return false; } /* * heap_hot_search_buffer - search HOT chain for tuple satisfying snapshot * * On entry, *tid is the TID of a tuple (either a simple tuple, or the root * of a HOT chain), and buffer is the buffer holding this tuple. We search * for the first chain member satisfying the given snapshot. If one is * found, we update *tid to reference that tuple's offset number, and * return TRUE. If no match, return FALSE without modifying *tid. * * heapTuple is a caller-supplied buffer. When a match is found, we return * the tuple here, in addition to updating *tid. If no match is found, the * contents of this buffer on return are undefined. * * If all_dead is not NULL, we check non-visible tuples to see if they are * globally dead; *all_dead is set TRUE if all members of the HOT chain * are vacuumable, FALSE if not. * * Unlike heap_fetch, the caller must already have pin and (at least) share * lock on the buffer; it is still pinned/locked at exit. Also unlike * heap_fetch, we do not report any pgstats count; caller may do so if wanted. */ bool heap_hot_search_buffer(ItemPointer tid, Relation relation, Buffer buffer, Snapshot snapshot, HeapTuple heapTuple, bool *all_dead, bool first_call) { Page dp = (Page) BufferGetPage(buffer); TransactionId prev_xmax = InvalidTransactionId; OffsetNumber offnum; bool at_chain_start; bool valid; bool skip; /* If this is not the first call, previous call returned a (live!) tuple */ if (all_dead) *all_dead = first_call; Assert(TransactionIdIsValid(RecentGlobalXmin)); Assert(ItemPointerGetBlockNumber(tid) == BufferGetBlockNumber(buffer)); offnum = ItemPointerGetOffsetNumber(tid); at_chain_start = first_call; skip = !first_call; /* Scan through possible multiple members of HOT-chain */ for (;;) { ItemId lp; /* check for bogus TID */ if (offnum < FirstOffsetNumber || offnum > PageGetMaxOffsetNumber(dp)) break; lp = PageGetItemId(dp, offnum); /* check for unused, dead, or redirected items */ if (!ItemIdIsNormal(lp)) { /* We should only see a redirect at start of chain */ if (ItemIdIsRedirected(lp) && at_chain_start) { /* Follow the redirect */ offnum = ItemIdGetRedirect(lp); at_chain_start = false; continue; } /* else must be end of chain */ break; } heapTuple->t_data = (HeapTupleHeader) PageGetItem(dp, lp); heapTuple->t_len = ItemIdGetLength(lp); heapTuple->t_tableOid = relation->rd_id; heapTuple->t_self = *tid; /* * Shouldn't see a HEAP_ONLY tuple at chain start. */ if (at_chain_start && HeapTupleIsHeapOnly(heapTuple)) break; /* * The xmin should match the previous xmax value, else chain is * broken. */ if (TransactionIdIsValid(prev_xmax) && !TransactionIdEquals(prev_xmax, HeapTupleHeaderGetXmin(heapTuple->t_data))) break; /* * When first_call is true (and thus, skip is initially false) we'll * return the first tuple we find. But on later passes, heapTuple * will initially be pointing to the tuple we returned last time. * Returning it again would be incorrect (and would loop forever), so * we skip it and return the next match we find. */ if (!skip) { /* If it's visible per the snapshot, we must return it */ valid = HeapTupleSatisfiesVisibility(heapTuple, snapshot, buffer); CheckForSerializableConflictOut(valid, relation, heapTuple, buffer, snapshot); if (valid) { ItemPointerSetOffsetNumber(tid, offnum); PredicateLockTuple(relation, heapTuple, snapshot); if (all_dead) *all_dead = false; return true; } } skip = false; /* * If we can't see it, maybe no one else can either. At caller * request, check whether all chain members are dead to all * transactions. */ if (all_dead && *all_dead && !HeapTupleIsSurelyDead(heapTuple->t_data, RecentGlobalXmin)) *all_dead = false; /* * Check to see if HOT chain continues past this tuple; if so fetch * the next offnum and loop around. */ if (HeapTupleIsHotUpdated(heapTuple)) { Assert(ItemPointerGetBlockNumber(&heapTuple->t_data->t_ctid) == ItemPointerGetBlockNumber(tid)); offnum = ItemPointerGetOffsetNumber(&heapTuple->t_data->t_ctid); at_chain_start = false; prev_xmax = HeapTupleHeaderGetUpdateXid(heapTuple->t_data); } else break; /* end of chain */ } return false; } /* * heap_hot_search - search HOT chain for tuple satisfying snapshot * * This has the same API as heap_hot_search_buffer, except that the caller * does not provide the buffer containing the page, rather we access it * locally. */ bool heap_hot_search(ItemPointer tid, Relation relation, Snapshot snapshot, bool *all_dead) { bool result; Buffer buffer; HeapTupleData heapTuple; buffer = ReadBuffer(relation, ItemPointerGetBlockNumber(tid)); LockBuffer(buffer, BUFFER_LOCK_SHARE); result = heap_hot_search_buffer(tid, relation, buffer, snapshot, &heapTuple, all_dead, true); LockBuffer(buffer, BUFFER_LOCK_UNLOCK); ReleaseBuffer(buffer); return result; } /* * heap_get_latest_tid - get the latest tid of a specified tuple * * Actually, this gets the latest version that is visible according to * the passed snapshot. You can pass SnapshotDirty to get the very latest, * possibly uncommitted version. * * *tid is both an input and an output parameter: it is updated to * show the latest version of the row. Note that it will not be changed * if no version of the row passes the snapshot test. */ void heap_get_latest_tid(Relation relation, Snapshot snapshot, ItemPointer tid) { BlockNumber blk; ItemPointerData ctid; TransactionId priorXmax; /* this is to avoid Assert failures on bad input */ if (!ItemPointerIsValid(tid)) return; /* * Since this can be called with user-supplied TID, don't trust the input * too much. (RelationGetNumberOfBlocks is an expensive check, so we * don't check t_ctid links again this way. Note that it would not do to * call it just once and save the result, either.) */ blk = ItemPointerGetBlockNumber(tid); if (blk >= RelationGetNumberOfBlocks(relation)) elog(ERROR, "block number %u is out of range for relation \"%s\"", blk, RelationGetRelationName(relation)); /* * Loop to chase down t_ctid links. At top of loop, ctid is the tuple we * need to examine, and *tid is the TID we will return if ctid turns out * to be bogus. * * Note that we will loop until we reach the end of the t_ctid chain. * Depending on the snapshot passed, there might be at most one visible * version of the row, but we don't try to optimize for that. */ ctid = *tid; priorXmax = InvalidTransactionId; /* cannot check first XMIN */ for (;;) { Buffer buffer; Page page; OffsetNumber offnum; ItemId lp; HeapTupleData tp; bool valid; /* * Read, pin, and lock the page. */ buffer = ReadBuffer(relation, ItemPointerGetBlockNumber(&ctid)); LockBuffer(buffer, BUFFER_LOCK_SHARE); page = BufferGetPage(buffer); /* * Check for bogus item number. This is not treated as an error * condition because it can happen while following a t_ctid link. We * just assume that the prior tid is OK and return it unchanged. */ offnum = ItemPointerGetOffsetNumber(&ctid); if (offnum < FirstOffsetNumber || offnum > PageGetMaxOffsetNumber(page)) { UnlockReleaseBuffer(buffer); break; } lp = PageGetItemId(page, offnum); if (!ItemIdIsNormal(lp)) { UnlockReleaseBuffer(buffer); break; } /* OK to access the tuple */ tp.t_self = ctid; tp.t_data = (HeapTupleHeader) PageGetItem(page, lp); tp.t_len = ItemIdGetLength(lp); /* * After following a t_ctid link, we might arrive at an unrelated * tuple. Check for XMIN match. */ if (TransactionIdIsValid(priorXmax) && !TransactionIdEquals(priorXmax, HeapTupleHeaderGetXmin(tp.t_data))) { UnlockReleaseBuffer(buffer); break; } /* * Check time qualification of tuple; if visible, set it as the new * result candidate. */ valid = HeapTupleSatisfiesVisibility(&tp, snapshot, buffer); CheckForSerializableConflictOut(valid, relation, &tp, buffer, snapshot); if (valid) *tid = ctid; /* * If there's a valid t_ctid link, follow it, else we're done. */ if ((tp.t_data->t_infomask & HEAP_XMAX_INVALID) || HeapTupleHeaderIsOnlyLocked(tp.t_data) || ItemPointerEquals(&tp.t_self, &tp.t_data->t_ctid)) { UnlockReleaseBuffer(buffer); break; } ctid = tp.t_data->t_ctid; priorXmax = HeapTupleHeaderGetUpdateXid(tp.t_data); UnlockReleaseBuffer(buffer); } /* end of loop */ } /* * UpdateXmaxHintBits - update tuple hint bits after xmax transaction ends * * This is called after we have waited for the XMAX transaction to terminate. * If the transaction aborted, we guarantee the XMAX_INVALID hint bit will * be set on exit. If the transaction committed, we set the XMAX_COMMITTED * hint bit if possible --- but beware that that may not yet be possible, * if the transaction committed asynchronously. * * Note that if the transaction was a locker only, we set HEAP_XMAX_INVALID * even if it commits. * * Hence callers should look only at XMAX_INVALID. * * Note this is not allowed for tuples whose xmax is a multixact. */ static void UpdateXmaxHintBits(HeapTupleHeader tuple, Buffer buffer, TransactionId xid) { Assert(TransactionIdEquals(HeapTupleHeaderGetRawXmax(tuple), xid)); Assert(!(tuple->t_infomask & HEAP_XMAX_IS_MULTI)); if (!(tuple->t_infomask & (HEAP_XMAX_COMMITTED | HEAP_XMAX_INVALID))) { if (!HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_infomask) && TransactionIdDidCommit(xid)) HeapTupleSetHintBits(tuple, buffer, HEAP_XMAX_COMMITTED, xid); else HeapTupleSetHintBits(tuple, buffer, HEAP_XMAX_INVALID, InvalidTransactionId); } } /* * GetBulkInsertState - prepare status object for a bulk insert */ BulkInsertState GetBulkInsertState(void) { BulkInsertState bistate; bistate = (BulkInsertState) palloc(sizeof(BulkInsertStateData)); bistate->strategy = GetAccessStrategy(BAS_BULKWRITE); bistate->current_buf = InvalidBuffer; return bistate; } /* * FreeBulkInsertState - clean up after finishing a bulk insert */ void FreeBulkInsertState(BulkInsertState bistate) { if (bistate->current_buf != InvalidBuffer) ReleaseBuffer(bistate->current_buf); FreeAccessStrategy(bistate->strategy); pfree(bistate); } /* * heap_insert - insert tuple into a heap * * The new tuple is stamped with current transaction ID and the specified * command ID. * * If the HEAP_INSERT_SKIP_WAL option is specified, the new tuple is not * logged in WAL, even for a non-temp relation. Safe usage of this behavior * requires that we arrange that all new tuples go into new pages not * containing any tuples from other transactions, and that the relation gets * fsync'd before commit. (See also heap_sync() comments) * * The HEAP_INSERT_SKIP_FSM option is passed directly to * RelationGetBufferForTuple, which see for more info. * * HEAP_INSERT_FROZEN should only be specified for inserts into * relfilenodes created during the current subtransaction and when * there are no prior snapshots or pre-existing portals open. * This causes rows to be frozen, which is an MVCC violation and * requires explicit options chosen by user. * * Note that these options will be applied when inserting into the heap's * TOAST table, too, if the tuple requires any out-of-line data. * * The BulkInsertState object (if any; bistate can be NULL for default * behavior) is also just passed through to RelationGetBufferForTuple. * * The return value is the OID assigned to the tuple (either here or by the * caller), or InvalidOid if no OID. The header fields of *tup are updated * to match the stored tuple; in particular tup->t_self receives the actual * TID where the tuple was stored. But note that any toasting of fields * within the tuple data is NOT reflected into *tup. */ Oid heap_insert(Relation relation, HeapTuple tup, CommandId cid, int options, BulkInsertState bistate) { TransactionId xid = GetCurrentTransactionId(); HeapTuple heaptup; Buffer buffer; Buffer vmbuffer = InvalidBuffer; bool all_visible_cleared = false; /* * Fill in tuple header fields, assign an OID, and toast the tuple if * necessary. * * Note: below this point, heaptup is the data we actually intend to store * into the relation; tup is the caller's original untoasted data. */ heaptup = heap_prepare_insert(relation, tup, xid, cid, options); /* * We're about to do the actual insert -- but check for conflict first, to * avoid possibly having to roll back work we've just done. * * For a heap insert, we only need to check for table-level SSI locks. Our * new tuple can't possibly conflict with existing tuple locks, and heap * page locks are only consolidated versions of tuple locks; they do not * lock "gaps" as index page locks do. So we don't need to identify a * buffer before making the call. */ CheckForSerializableConflictIn(relation, NULL, InvalidBuffer); /* * Find buffer to insert this tuple into. If the page is all visible, * this will also pin the requisite visibility map page. */ buffer = RelationGetBufferForTuple(relation, heaptup->t_len, InvalidBuffer, options, bistate, &vmbuffer, NULL); /* NO EREPORT(ERROR) from here till changes are logged */ START_CRIT_SECTION(); RelationPutHeapTuple(relation, buffer, heaptup); if (PageIsAllVisible(BufferGetPage(buffer))) { all_visible_cleared = true; PageClearAllVisible(BufferGetPage(buffer)); visibilitymap_clear(relation, ItemPointerGetBlockNumber(&(heaptup->t_self)), vmbuffer); } /* * XXX Should we set PageSetPrunable on this page ? * * The inserting transaction may eventually abort thus making this tuple * DEAD and hence available for pruning. Though we don't want to optimize * for aborts, if no other tuple in this page is UPDATEd/DELETEd, the * aborted tuple will never be pruned until next vacuum is triggered. * * If you do add PageSetPrunable here, add it in heap_xlog_insert too. */ MarkBufferDirty(buffer); /* XLOG stuff */ if (!(options & HEAP_INSERT_SKIP_WAL) && RelationNeedsWAL(relation)) { xl_heap_insert xlrec; xl_heap_header xlhdr; XLogRecPtr recptr; XLogRecData rdata[3]; Page page = BufferGetPage(buffer); uint8 info = XLOG_HEAP_INSERT; xlrec.all_visible_cleared = all_visible_cleared; xlrec.target.node = relation->rd_node; xlrec.target.tid = heaptup->t_self; rdata[0].data = (char *) &xlrec; rdata[0].len = SizeOfHeapInsert; rdata[0].buffer = InvalidBuffer; rdata[0].next = &(rdata[1]); xlhdr.t_infomask2 = heaptup->t_data->t_infomask2; xlhdr.t_infomask = heaptup->t_data->t_infomask; xlhdr.t_hoff = heaptup->t_data->t_hoff; /* * note we mark rdata[1] as belonging to buffer; if XLogInsert decides * to write the whole page to the xlog, we don't need to store * xl_heap_header in the xlog. */ rdata[1].data = (char *) &xlhdr; rdata[1].len = SizeOfHeapHeader; rdata[1].buffer = buffer; rdata[1].buffer_std = true; rdata[1].next = &(rdata[2]); /* PG73FORMAT: write bitmap [+ padding] [+ oid] + data */ rdata[2].data = (char *) heaptup->t_data + offsetof(HeapTupleHeaderData, t_bits); rdata[2].len = heaptup->t_len - offsetof(HeapTupleHeaderData, t_bits); rdata[2].buffer = buffer; rdata[2].buffer_std = true; rdata[2].next = NULL; /* * If this is the single and first tuple on page, we can reinit the * page instead of restoring the whole thing. Set flag, and hide * buffer references from XLogInsert. */ if (ItemPointerGetOffsetNumber(&(heaptup->t_self)) == FirstOffsetNumber && PageGetMaxOffsetNumber(page) == FirstOffsetNumber) { info |= XLOG_HEAP_INIT_PAGE; rdata[1].buffer = rdata[2].buffer = InvalidBuffer; } recptr = XLogInsert(RM_HEAP_ID, info, rdata); PageSetLSN(page, recptr); } END_CRIT_SECTION(); UnlockReleaseBuffer(buffer); if (vmbuffer != InvalidBuffer) ReleaseBuffer(vmbuffer); /* * If tuple is cachable, mark it for invalidation from the caches in case * we abort. Note it is OK to do this after releasing the buffer, because * the heaptup data structure is all in local memory, not in the shared * buffer. */ CacheInvalidateHeapTuple(relation, heaptup, NULL); pgstat_count_heap_insert(relation, 1); /* * If heaptup is a private copy, release it. Don't forget to copy t_self * back to the caller's image, too. */ if (heaptup != tup) { tup->t_self = heaptup->t_self; heap_freetuple(heaptup); } return HeapTupleGetOid(tup); } /* * Subroutine for heap_insert(). Prepares a tuple for insertion. This sets the * tuple header fields, assigns an OID, and toasts the tuple if necessary. * Returns a toasted version of the tuple if it was toasted, or the original * tuple if not. Note that in any case, the header fields are also set in * the original tuple. */ static HeapTuple heap_prepare_insert(Relation relation, HeapTuple tup, TransactionId xid, CommandId cid, int options) { if (relation->rd_rel->relhasoids) { #ifdef NOT_USED /* this is redundant with an Assert in HeapTupleSetOid */ Assert(tup->t_data->t_infomask & HEAP_HASOID); #endif /* * If the object id of this tuple has already been assigned, trust the * caller. There are a couple of ways this can happen. At initial db * creation, the backend program sets oids for tuples. When we define * an index, we set the oid. Finally, in the future, we may allow * users to set their own object ids in order to support a persistent * object store (objects need to contain pointers to one another). */ if (!OidIsValid(HeapTupleGetOid(tup))) HeapTupleSetOid(tup, GetNewOid(relation)); } else { /* check there is not space for an OID */ Assert(!(tup->t_data->t_infomask & HEAP_HASOID)); } tup->t_data->t_infomask &= ~(HEAP_XACT_MASK); tup->t_data->t_infomask2 &= ~(HEAP2_XACT_MASK); tup->t_data->t_infomask |= HEAP_XMAX_INVALID; if (options & HEAP_INSERT_FROZEN) { tup->t_data->t_infomask |= HEAP_XMIN_COMMITTED; HeapTupleHeaderSetXmin(tup->t_data, FrozenTransactionId); } else HeapTupleHeaderSetXmin(tup->t_data, xid); HeapTupleHeaderSetCmin(tup->t_data, cid); HeapTupleHeaderSetXmax(tup->t_data, 0); /* for cleanliness */ tup->t_tableOid = RelationGetRelid(relation); /* * If the new tuple is too big for storage or contains already toasted * out-of-line attributes from some other relation, invoke the toaster. */ if (relation->rd_rel->relkind != RELKIND_RELATION && relation->rd_rel->relkind != RELKIND_MATVIEW) { /* toast table entries should never be recursively toasted */ Assert(!HeapTupleHasExternal(tup)); return tup; } else if (HeapTupleHasExternal(tup) || tup->t_len > TOAST_TUPLE_THRESHOLD) return toast_insert_or_update(relation, tup, NULL, options); else return tup; } /* * heap_multi_insert - insert multiple tuple into a heap * * This is like heap_insert(), but inserts multiple tuples in one operation. * That's faster than calling heap_insert() in a loop, because when multiple * tuples can be inserted on a single page, we can write just a single WAL * record covering all of them, and only need to lock/unlock the page once. * * Note: this leaks memory into the current memory context. You can create a * temporary context before calling this, if that's a problem. */ void heap_multi_insert(Relation relation, HeapTuple *tuples, int ntuples, CommandId cid, int options, BulkInsertState bistate) { TransactionId xid = GetCurrentTransactionId(); HeapTuple *heaptuples; int i; int ndone; char *scratch = NULL; Page page; bool needwal; Size saveFreeSpace; needwal = !(options & HEAP_INSERT_SKIP_WAL) && RelationNeedsWAL(relation); saveFreeSpace = RelationGetTargetPageFreeSpace(relation, HEAP_DEFAULT_FILLFACTOR); /* Toast and set header data in all the tuples */ heaptuples = palloc(ntuples * sizeof(HeapTuple)); for (i = 0; i < ntuples; i++) heaptuples[i] = heap_prepare_insert(relation, tuples[i], xid, cid, options); /* * Allocate some memory to use for constructing the WAL record. Using * palloc() within a critical section is not safe, so we allocate this * beforehand. */ if (needwal) scratch = palloc(BLCKSZ); /* * We're about to do the actual inserts -- but check for conflict first, * to avoid possibly having to roll back work we've just done. * * For a heap insert, we only need to check for table-level SSI locks. Our * new tuple can't possibly conflict with existing tuple locks, and heap * page locks are only consolidated versions of tuple locks; they do not * lock "gaps" as index page locks do. So we don't need to identify a * buffer before making the call. */ CheckForSerializableConflictIn(relation, NULL, InvalidBuffer); ndone = 0; while (ndone < ntuples) { Buffer buffer; Buffer vmbuffer = InvalidBuffer; bool all_visible_cleared = false; int nthispage; /* * Find buffer where at least the next tuple will fit. If the page is * all-visible, this will also pin the requisite visibility map page. */ buffer = RelationGetBufferForTuple(relation, heaptuples[ndone]->t_len, InvalidBuffer, options, bistate, &vmbuffer, NULL); page = BufferGetPage(buffer); /* NO EREPORT(ERROR) from here till changes are logged */ START_CRIT_SECTION(); /* * RelationGetBufferForTuple has ensured that the first tuple fits. * Put that on the page, and then as many other tuples as fit. */ RelationPutHeapTuple(relation, buffer, heaptuples[ndone]); for (nthispage = 1; ndone + nthispage < ntuples; nthispage++) { HeapTuple heaptup = heaptuples[ndone + nthispage]; if (PageGetHeapFreeSpace(page) < MAXALIGN(heaptup->t_len) + saveFreeSpace) break; RelationPutHeapTuple(relation, buffer, heaptup); } if (PageIsAllVisible(page)) { all_visible_cleared = true; PageClearAllVisible(page); visibilitymap_clear(relation, BufferGetBlockNumber(buffer), vmbuffer); } /* * XXX Should we set PageSetPrunable on this page ? See heap_insert() */ MarkBufferDirty(buffer); /* XLOG stuff */ if (needwal) { XLogRecPtr recptr; xl_heap_multi_insert *xlrec; XLogRecData rdata[2]; uint8 info = XLOG_HEAP2_MULTI_INSERT; char *tupledata; int totaldatalen; char *scratchptr = scratch; bool init; /* * If the page was previously empty, we can reinit the page * instead of restoring the whole thing. */ init = (ItemPointerGetOffsetNumber(&(heaptuples[ndone]->t_self)) == FirstOffsetNumber && PageGetMaxOffsetNumber(page) == FirstOffsetNumber + nthispage - 1); /* allocate xl_heap_multi_insert struct from the scratch area */ xlrec = (xl_heap_multi_insert *) scratchptr; scratchptr += SizeOfHeapMultiInsert; /* * Allocate offsets array. Unless we're reinitializing the page, * in that case the tuples are stored in order starting at * FirstOffsetNumber and we don't need to store the offsets * explicitly. */ if (!init) scratchptr += nthispage * sizeof(OffsetNumber); /* the rest of the scratch space is used for tuple data */ tupledata = scratchptr; xlrec->all_visible_cleared = all_visible_cleared; xlrec->node = relation->rd_node; xlrec->blkno = BufferGetBlockNumber(buffer); xlrec->ntuples = nthispage; /* * Write out an xl_multi_insert_tuple and the tuple data itself * for each tuple. */ for (i = 0; i < nthispage; i++) { HeapTuple heaptup = heaptuples[ndone + i]; xl_multi_insert_tuple *tuphdr; int datalen; if (!init) xlrec->offsets[i] = ItemPointerGetOffsetNumber(&heaptup->t_self); /* xl_multi_insert_tuple needs two-byte alignment. */ tuphdr = (xl_multi_insert_tuple *) SHORTALIGN(scratchptr); scratchptr = ((char *) tuphdr) + SizeOfMultiInsertTuple; tuphdr->t_infomask2 = heaptup->t_data->t_infomask2; tuphdr->t_infomask = heaptup->t_data->t_infomask; tuphdr->t_hoff = heaptup->t_data->t_hoff; /* write bitmap [+ padding] [+ oid] + data */ datalen = heaptup->t_len - offsetof(HeapTupleHeaderData, t_bits); memcpy(scratchptr, (char *) heaptup->t_data + offsetof(HeapTupleHeaderData, t_bits), datalen); tuphdr->datalen = datalen; scratchptr += datalen; } totaldatalen = scratchptr - tupledata; Assert((scratchptr - scratch) < BLCKSZ); rdata[0].data = (char *) xlrec; rdata[0].len = tupledata - scratch; rdata[0].buffer = InvalidBuffer; rdata[0].next = &rdata[1]; rdata[1].data = tupledata; rdata[1].len = totaldatalen; rdata[1].buffer = buffer; rdata[1].buffer_std = true; rdata[1].next = NULL; /* * If we're going to reinitialize the whole page using the WAL * record, hide buffer reference from XLogInsert. */ if (init) { rdata[1].buffer = InvalidBuffer; info |= XLOG_HEAP_INIT_PAGE; } recptr = XLogInsert(RM_HEAP2_ID, info, rdata); PageSetLSN(page, recptr); } END_CRIT_SECTION(); UnlockReleaseBuffer(buffer); if (vmbuffer != InvalidBuffer) ReleaseBuffer(vmbuffer); ndone += nthispage; } /* * If tuples are cachable, mark them for invalidation from the caches in * case we abort. Note it is OK to do this after releasing the buffer, * because the heaptuples data structure is all in local memory, not in * the shared buffer. */ if (IsSystemRelation(relation)) { for (i = 0; i < ntuples; i++) CacheInvalidateHeapTuple(relation, heaptuples[i], NULL); } /* * Copy t_self fields back to the caller's original tuples. This does * nothing for untoasted tuples (tuples[i] == heaptuples[i)], but it's * probably faster to always copy than check. */ for (i = 0; i < ntuples; i++) tuples[i]->t_self = heaptuples[i]->t_self; pgstat_count_heap_insert(relation, ntuples); } /* * simple_heap_insert - insert a tuple * * Currently, this routine differs from heap_insert only in supplying * a default command ID and not allowing access to the speedup options. * * This should be used rather than using heap_insert directly in most places * where we are modifying system catalogs. */ Oid simple_heap_insert(Relation relation, HeapTuple tup) { return heap_insert(relation, tup, GetCurrentCommandId(true), 0, NULL); } /* * Given infomask/infomask2, compute the bits that must be saved in the * "infobits" field of xl_heap_delete, xl_heap_update, xl_heap_lock, * xl_heap_lock_updated WAL records. * * See fix_infomask_from_infobits. */ static uint8 compute_infobits(uint16 infomask, uint16 infomask2) { return ((infomask & HEAP_XMAX_IS_MULTI) != 0 ? XLHL_XMAX_IS_MULTI : 0) | ((infomask & HEAP_XMAX_LOCK_ONLY) != 0 ? XLHL_XMAX_LOCK_ONLY : 0) | ((infomask & HEAP_XMAX_EXCL_LOCK) != 0 ? XLHL_XMAX_EXCL_LOCK : 0) | /* note we ignore HEAP_XMAX_SHR_LOCK here */ ((infomask & HEAP_XMAX_KEYSHR_LOCK) != 0 ? XLHL_XMAX_KEYSHR_LOCK : 0) | ((infomask2 & HEAP_KEYS_UPDATED) != 0 ? XLHL_KEYS_UPDATED : 0); } /* * heap_delete - delete a tuple * * NB: do not call this directly unless you are prepared to deal with * concurrent-update conditions. Use simple_heap_delete instead. * * relation - table to be modified (caller must hold suitable lock) * tid - TID of tuple to be deleted * cid - delete command ID (used for visibility test, and stored into * cmax if successful) * crosscheck - if not InvalidSnapshot, also check tuple against this * wait - true if should wait for any conflicting update to commit/abort * hufd - output parameter, filled in failure cases (see below) * * Normal, successful return value is HeapTupleMayBeUpdated, which * actually means we did delete it. Failure return codes are * HeapTupleSelfUpdated, HeapTupleUpdated, or HeapTupleBeingUpdated * (the last only possible if wait == false). * * In the failure cases, the routine fills *hufd with the tuple's t_ctid, * t_xmax (resolving a possible MultiXact, if necessary), and t_cmax * (the last only for HeapTupleSelfUpdated, since we * cannot obtain cmax from a combocid generated by another transaction). * See comments for struct HeapUpdateFailureData for additional info. */ HTSU_Result heap_delete(Relation relation, ItemPointer tid, CommandId cid, Snapshot crosscheck, bool wait, HeapUpdateFailureData *hufd) { HTSU_Result result; TransactionId xid = GetCurrentTransactionId(); ItemId lp; HeapTupleData tp; Page page; BlockNumber block; Buffer buffer; Buffer vmbuffer = InvalidBuffer; TransactionId new_xmax; uint16 new_infomask, new_infomask2; bool have_tuple_lock = false; bool iscombo; bool all_visible_cleared = false; Assert(ItemPointerIsValid(tid)); block = ItemPointerGetBlockNumber(tid); buffer = ReadBuffer(relation, block); page = BufferGetPage(buffer); /* * Before locking the buffer, pin the visibility map page if it appears to * be necessary. Since we haven't got the lock yet, someone else might be * in the middle of changing this, so we'll need to recheck after we have * the lock. */ if (PageIsAllVisible(page)) visibilitymap_pin(relation, block, &vmbuffer); LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE); /* * If we didn't pin the visibility map page and the page has become all * visible while we were busy locking the buffer, we'll have to unlock and * re-lock, to avoid holding the buffer lock across an I/O. That's a bit * unfortunate, but hopefully shouldn't happen often. */ if (vmbuffer == InvalidBuffer && PageIsAllVisible(page)) { LockBuffer(buffer, BUFFER_LOCK_UNLOCK); visibilitymap_pin(relation, block, &vmbuffer); LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE); } lp = PageGetItemId(page, ItemPointerGetOffsetNumber(tid)); Assert(ItemIdIsNormal(lp)); tp.t_data = (HeapTupleHeader) PageGetItem(page, lp); tp.t_len = ItemIdGetLength(lp); tp.t_self = *tid; l1: result = HeapTupleSatisfiesUpdate(tp.t_data, cid, buffer); if (result == HeapTupleInvisible) { UnlockReleaseBuffer(buffer); elog(ERROR, "attempted to delete invisible tuple"); } else if (result == HeapTupleBeingUpdated && wait) { TransactionId xwait; uint16 infomask; /* must copy state data before unlocking buffer */ xwait = HeapTupleHeaderGetRawXmax(tp.t_data); infomask = tp.t_data->t_infomask; LockBuffer(buffer, BUFFER_LOCK_UNLOCK); /* * Acquire tuple lock to establish our priority for the tuple (see * heap_lock_tuple). LockTuple will release us when we are * next-in-line for the tuple. * * If we are forced to "start over" below, we keep the tuple lock; * this arranges that we stay at the head of the line while rechecking * tuple state. */ if (!have_tuple_lock) { LockTupleTuplock(relation, &(tp.t_self), LockTupleExclusive); have_tuple_lock = true; } /* * Sleep until concurrent transaction ends. Note that we don't care * which lock mode the locker has, because we need the strongest one. */ if (infomask & HEAP_XMAX_IS_MULTI) { /* wait for multixact */ MultiXactIdWait((MultiXactId) xwait, MultiXactStatusUpdate, NULL, infomask); LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE); /* * If xwait had just locked the tuple then some other xact could * update this tuple before we get to this point. Check for xmax * change, and start over if so. */ if (!(tp.t_data->t_infomask & HEAP_XMAX_IS_MULTI) || !TransactionIdEquals(HeapTupleHeaderGetRawXmax(tp.t_data), xwait)) goto l1; /* * You might think the multixact is necessarily done here, but not * so: it could have surviving members, namely our own xact or * other subxacts of this backend. It is legal for us to delete * the tuple in either case, however (the latter case is * essentially a situation of upgrading our former shared lock to * exclusive). We don't bother changing the on-disk hint bits * since we are about to overwrite the xmax altogether. */ } else { /* wait for regular transaction to end */ XactLockTableWait(xwait); LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE); /* * xwait is done, but if xwait had just locked the tuple then some * other xact could update this tuple before we get to this point. * Check for xmax change, and start over if so. */ if ((tp.t_data->t_infomask & HEAP_XMAX_IS_MULTI) || !TransactionIdEquals(HeapTupleHeaderGetRawXmax(tp.t_data), xwait)) goto l1; /* Otherwise check if it committed or aborted */ UpdateXmaxHintBits(tp.t_data, buffer, xwait); } /* * We may overwrite if previous xmax aborted, or if it committed but * only locked the tuple without updating it. */ if ((tp.t_data->t_infomask & HEAP_XMAX_INVALID) || HEAP_XMAX_IS_LOCKED_ONLY(tp.t_data->t_infomask) || HeapTupleHeaderIsOnlyLocked(tp.t_data)) result = HeapTupleMayBeUpdated; else result = HeapTupleUpdated; } if (crosscheck != InvalidSnapshot && result == HeapTupleMayBeUpdated) { /* Perform additional check for transaction-snapshot mode RI updates */ if (!HeapTupleSatisfiesVisibility(&tp, crosscheck, buffer)) result = HeapTupleUpdated; } if (result != HeapTupleMayBeUpdated) { Assert(result == HeapTupleSelfUpdated || result == HeapTupleUpdated || result == HeapTupleBeingUpdated); Assert(!(tp.t_data->t_infomask & HEAP_XMAX_INVALID)); hufd->ctid = tp.t_data->t_ctid; hufd->xmax = HeapTupleHeaderGetUpdateXid(tp.t_data); if (result == HeapTupleSelfUpdated) hufd->cmax = HeapTupleHeaderGetCmax(tp.t_data); else hufd->cmax = 0; /* for lack of an InvalidCommandId value */ UnlockReleaseBuffer(buffer); if (have_tuple_lock) UnlockTupleTuplock(relation, &(tp.t_self), LockTupleExclusive); if (vmbuffer != InvalidBuffer) ReleaseBuffer(vmbuffer); return result; } /* * We're about to do the actual delete -- check for conflict first, to * avoid possibly having to roll back work we've just done. */ CheckForSerializableConflictIn(relation, &tp, buffer); /* replace cid with a combo cid if necessary */ HeapTupleHeaderAdjustCmax(tp.t_data, &cid, &iscombo); START_CRIT_SECTION(); /* * If this transaction commits, the tuple will become DEAD sooner or * later. Set flag that this page is a candidate for pruning once our xid * falls below the OldestXmin horizon. If the transaction finally aborts, * the subsequent page pruning will be a no-op and the hint will be * cleared. */ PageSetPrunable(page, xid); if (PageIsAllVisible(page)) { all_visible_cleared = true; PageClearAllVisible(page); visibilitymap_clear(relation, BufferGetBlockNumber(buffer), vmbuffer); } /* * If this is the first possibly-multixact-able operation in the current * transaction, set my per-backend OldestMemberMXactId setting. We can be * certain that the transaction will never become a member of any older * MultiXactIds than that. (We have to do this even if we end up just * using our own TransactionId below, since some other backend could * incorporate our XID into a MultiXact immediately afterwards.) */ MultiXactIdSetOldestMember(); compute_new_xmax_infomask(HeapTupleHeaderGetRawXmax(tp.t_data), tp.t_data->t_infomask, tp.t_data->t_infomask2, xid, LockTupleExclusive, true, &new_xmax, &new_infomask, &new_infomask2); /* store transaction information of xact deleting the tuple */ tp.t_data->t_infomask &= ~(HEAP_XMAX_BITS | HEAP_MOVED); tp.t_data->t_infomask2 &= ~HEAP_KEYS_UPDATED; tp.t_data->t_infomask |= new_infomask; tp.t_data->t_infomask2 |= new_infomask2; HeapTupleHeaderClearHotUpdated(tp.t_data); HeapTupleHeaderSetXmax(tp.t_data, new_xmax); HeapTupleHeaderSetCmax(tp.t_data, cid, iscombo); /* Make sure there is no forward chain link in t_ctid */ tp.t_data->t_ctid = tp.t_self; MarkBufferDirty(buffer); /* XLOG stuff */ if (RelationNeedsWAL(relation)) { xl_heap_delete xlrec; XLogRecPtr recptr; XLogRecData rdata[2]; xlrec.all_visible_cleared = all_visible_cleared; xlrec.infobits_set = compute_infobits(tp.t_data->t_infomask, tp.t_data->t_infomask2); xlrec.target.node = relation->rd_node; xlrec.target.tid = tp.t_self; xlrec.xmax = new_xmax; rdata[0].data = (char *) &xlrec; rdata[0].len = SizeOfHeapDelete; rdata[0].buffer = InvalidBuffer; rdata[0].next = &(rdata[1]); rdata[1].data = NULL; rdata[1].len = 0; rdata[1].buffer = buffer; rdata[1].buffer_std = true; rdata[1].next = NULL; recptr = XLogInsert(RM_HEAP_ID, XLOG_HEAP_DELETE, rdata); PageSetLSN(page, recptr); } END_CRIT_SECTION(); LockBuffer(buffer, BUFFER_LOCK_UNLOCK); if (vmbuffer != InvalidBuffer) ReleaseBuffer(vmbuffer); /* * If the tuple has toasted out-of-line attributes, we need to delete * those items too. We have to do this before releasing the buffer * because we need to look at the contents of the tuple, but it's OK to * release the content lock on the buffer first. */ if (relation->rd_rel->relkind != RELKIND_RELATION && relation->rd_rel->relkind != RELKIND_MATVIEW) { /* toast table entries should never be recursively toasted */ Assert(!HeapTupleHasExternal(&tp)); } else if (HeapTupleHasExternal(&tp)) toast_delete(relation, &tp); /* * Mark tuple for invalidation from system caches at next command * boundary. We have to do this before releasing the buffer because we * need to look at the contents of the tuple. */ CacheInvalidateHeapTuple(relation, &tp, NULL); /* Now we can release the buffer */ ReleaseBuffer(buffer); /* * Release the lmgr tuple lock, if we had it. */ if (have_tuple_lock) UnlockTupleTuplock(relation, &(tp.t_self), LockTupleExclusive); pgstat_count_heap_delete(relation); return HeapTupleMayBeUpdated; } /* * simple_heap_delete - delete a tuple * * This routine may be used to delete a tuple when concurrent updates of * the target tuple are not expected (for example, because we have a lock * on the relation associated with the tuple). Any failure is reported * via ereport(). */ void simple_heap_delete(Relation relation, ItemPointer tid) { HTSU_Result result; HeapUpdateFailureData hufd; result = heap_delete(relation, tid, GetCurrentCommandId(true), InvalidSnapshot, true /* wait for commit */ , &hufd); switch (result) { case HeapTupleSelfUpdated: /* Tuple was already updated in current command? */ elog(ERROR, "tuple already updated by self"); break; case HeapTupleMayBeUpdated: /* done successfully */ break; case HeapTupleUpdated: elog(ERROR, "tuple concurrently updated"); break; default: elog(ERROR, "unrecognized heap_delete status: %u", result); break; } } /* * heap_update - replace a tuple * * NB: do not call this directly unless you are prepared to deal with * concurrent-update conditions. Use simple_heap_update instead. * * relation - table to be modified (caller must hold suitable lock) * otid - TID of old tuple to be replaced * newtup - newly constructed tuple data to store * cid - update command ID (used for visibility test, and stored into * cmax/cmin if successful) * crosscheck - if not InvalidSnapshot, also check old tuple against this * wait - true if should wait for any conflicting update to commit/abort * hufd - output parameter, filled in failure cases (see below) * lockmode - output parameter, filled with lock mode acquired on tuple * * Normal, successful return value is HeapTupleMayBeUpdated, which * actually means we *did* update it. Failure return codes are * HeapTupleSelfUpdated, HeapTupleUpdated, or HeapTupleBeingUpdated * (the last only possible if wait == false). * * On success, the header fields of *newtup are updated to match the new * stored tuple; in particular, newtup->t_self is set to the TID where the * new tuple was inserted, and its HEAP_ONLY_TUPLE flag is set iff a HOT * update was done. However, any TOAST changes in the new tuple's * data are not reflected into *newtup. * * In the failure cases, the routine fills *hufd with the tuple's t_ctid, * t_xmax (resolving a possible MultiXact, if necessary), and t_cmax * (the last only for HeapTupleSelfUpdated, since we * cannot obtain cmax from a combocid generated by another transaction). * See comments for struct HeapUpdateFailureData for additional info. */ HTSU_Result heap_update(Relation relation, ItemPointer otid, HeapTuple newtup, CommandId cid, Snapshot crosscheck, bool wait, HeapUpdateFailureData *hufd, LockTupleMode *lockmode) { HTSU_Result result; TransactionId xid = GetCurrentTransactionId(); Bitmapset *hot_attrs; Bitmapset *key_attrs; ItemId lp; HeapTupleData oldtup; HeapTuple heaptup; Page page; BlockNumber block; MultiXactStatus mxact_status; Buffer buffer, newbuf, vmbuffer = InvalidBuffer, vmbuffer_new = InvalidBuffer; bool need_toast, already_marked; Size newtupsize, pagefree; bool have_tuple_lock = false; bool iscombo; bool satisfies_hot; bool satisfies_key; bool use_hot_update = false; bool key_intact; bool all_visible_cleared = false; bool all_visible_cleared_new = false; bool checked_lockers; bool locker_remains; TransactionId xmax_new_tuple, xmax_old_tuple; uint16 infomask_old_tuple, infomask2_old_tuple, infomask_new_tuple, infomask2_new_tuple; Assert(ItemPointerIsValid(otid)); /* * Fetch the list of attributes to be checked for HOT update. This is * wasted effort if we fail to update or have to put the new tuple on a * different page. But we must compute the list before obtaining buffer * lock --- in the worst case, if we are doing an update on one of the * relevant system catalogs, we could deadlock if we try to fetch the list * later. In any case, the relcache caches the data so this is usually * pretty cheap. * * Note that we get a copy here, so we need not worry about relcache flush * happening midway through. */ hot_attrs = RelationGetIndexAttrBitmap(relation, false); key_attrs = RelationGetIndexAttrBitmap(relation, true); block = ItemPointerGetBlockNumber(otid); buffer = ReadBuffer(relation, block); page = BufferGetPage(buffer); /* * Before locking the buffer, pin the visibility map page if it appears to * be necessary. Since we haven't got the lock yet, someone else might be * in the middle of changing this, so we'll need to recheck after we have * the lock. */ if (PageIsAllVisible(page)) visibilitymap_pin(relation, block, &vmbuffer); LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE); lp = PageGetItemId(page, ItemPointerGetOffsetNumber(otid)); Assert(ItemIdIsNormal(lp)); /* * Fill in enough data in oldtup for HeapSatisfiesHOTandKeyUpdate to work * properly. */ oldtup.t_tableOid = RelationGetRelid(relation); oldtup.t_data = (HeapTupleHeader) PageGetItem(page, lp); oldtup.t_len = ItemIdGetLength(lp); oldtup.t_self = *otid; /* the new tuple is ready, except for this: */ newtup->t_tableOid = RelationGetRelid(relation); /* Fill in OID for newtup */ if (relation->rd_rel->relhasoids) { #ifdef NOT_USED /* this is redundant with an Assert in HeapTupleSetOid */ Assert(newtup->t_data->t_infomask & HEAP_HASOID); #endif HeapTupleSetOid(newtup, HeapTupleGetOid(&oldtup)); } else { /* check there is not space for an OID */ Assert(!(newtup->t_data->t_infomask & HEAP_HASOID)); } /* * If we're not updating any "key" column, we can grab a weaker lock type. * This allows for more concurrency when we are running simultaneously * with foreign key checks. * * Note that if a column gets detoasted while executing the update, but * the value ends up being the same, this test will fail and we will use * the stronger lock. This is acceptable; the important case to optimize * is updates that don't manipulate key columns, not those that * serendipitiously arrive at the same key values. */ HeapSatisfiesHOTandKeyUpdate(relation, hot_attrs, key_attrs, &satisfies_hot, &satisfies_key, &oldtup, newtup); if (satisfies_key) { *lockmode = LockTupleNoKeyExclusive; mxact_status = MultiXactStatusNoKeyUpdate; key_intact = true; /* * If this is the first possibly-multixact-able operation in the * current transaction, set my per-backend OldestMemberMXactId * setting. We can be certain that the transaction will never become a * member of any older MultiXactIds than that. (We have to do this * even if we end up just using our own TransactionId below, since * some other backend could incorporate our XID into a MultiXact * immediately afterwards.) */ MultiXactIdSetOldestMember(); } else { *lockmode = LockTupleExclusive; mxact_status = MultiXactStatusUpdate; key_intact = false; } /* * Note: beyond this point, use oldtup not otid to refer to old tuple. * otid may very well point at newtup->t_self, which we will overwrite * with the new tuple's location, so there's great risk of confusion if we * use otid anymore. */ l2: checked_lockers = false; locker_remains = false; result = HeapTupleSatisfiesUpdate(oldtup.t_data, cid, buffer); /* see below about the "no wait" case */ Assert(result != HeapTupleBeingUpdated || wait); if (result == HeapTupleInvisible) { UnlockReleaseBuffer(buffer); elog(ERROR, "attempted to update invisible tuple"); } else if (result == HeapTupleBeingUpdated && wait) { TransactionId xwait; uint16 infomask; bool can_continue = false; checked_lockers = true; /* * XXX note that we don't consider the "no wait" case here. This * isn't a problem currently because no caller uses that case, but it * should be fixed if such a caller is introduced. It wasn't a * problem previously because this code would always wait, but now * that some tuple locks do not conflict with one of the lock modes we * use, it is possible that this case is interesting to handle * specially. * * This may cause failures with third-party code that calls * heap_update directly. */ /* must copy state data before unlocking buffer */ xwait = HeapTupleHeaderGetRawXmax(oldtup.t_data); infomask = oldtup.t_data->t_infomask; LockBuffer(buffer, BUFFER_LOCK_UNLOCK); /* * Acquire tuple lock to establish our priority for the tuple (see * heap_lock_tuple). LockTuple will release us when we are * next-in-line for the tuple. * * If we are forced to "start over" below, we keep the tuple lock; * this arranges that we stay at the head of the line while rechecking * tuple state. */ if (!have_tuple_lock) { LockTupleTuplock(relation, &(oldtup.t_self), *lockmode); have_tuple_lock = true; } /* * Now we have to do something about the existing locker. If it's a * multi, sleep on it; we might be awakened before it is completely * gone (or even not sleep at all in some cases); we need to preserve * it as locker, unless it is gone completely. * * If it's not a multi, we need to check for sleeping conditions * before actually going to sleep. If the update doesn't conflict * with the locks, we just continue without sleeping (but making sure * it is preserved). */ if (infomask & HEAP_XMAX_IS_MULTI) { TransactionId update_xact; int remain; /* wait for multixact */ MultiXactIdWait((MultiXactId) xwait, mxact_status, &remain, infomask); LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE); /* * If xwait had just locked the tuple then some other xact could * update this tuple before we get to this point. Check for xmax * change, and start over if so. */ if (!(oldtup.t_data->t_infomask & HEAP_XMAX_IS_MULTI) || !TransactionIdEquals(HeapTupleHeaderGetRawXmax(oldtup.t_data), xwait)) goto l2; /* * Note that the multixact may not be done by now. It could have * surviving members; our own xact or other subxacts of this * backend, and also any other concurrent transaction that locked * the tuple with KeyShare if we only got TupleLockUpdate. If * this is the case, we have to be careful to mark the updated * tuple with the surviving members in Xmax. * * Note that there could have been another update in the * MultiXact. In that case, we need to check whether it committed * or aborted. If it aborted we are safe to update it again; * otherwise there is an update conflict, and we have to return * HeapTupleUpdated below. * * In the LockTupleExclusive case, we still need to preserve the * surviving members: those would include the tuple locks we had * before this one, which are important to keep in case this * subxact aborts. */ update_xact = InvalidTransactionId; if (!HEAP_XMAX_IS_LOCKED_ONLY(oldtup.t_data->t_infomask)) update_xact = HeapTupleGetUpdateXid(oldtup.t_data); /* there was no UPDATE in the MultiXact; or it aborted. */ if (!TransactionIdIsValid(update_xact) || TransactionIdDidAbort(update_xact)) can_continue = true; locker_remains = remain != 0; } else { /* * If it's just a key-share locker, and we're not changing the key * columns, we don't need to wait for it to end; but we need to * preserve it as locker. */ if (HEAP_XMAX_IS_KEYSHR_LOCKED(infomask) && key_intact) { LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE); /* * recheck the locker; if someone else changed the tuple while * we weren't looking, start over. */ if ((oldtup.t_data->t_infomask & HEAP_XMAX_IS_MULTI) || !TransactionIdEquals(HeapTupleHeaderGetRawXmax(oldtup.t_data), xwait)) goto l2; can_continue = true; locker_remains = true; } else { /* wait for regular transaction to end */ XactLockTableWait(xwait); LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE); /* * xwait is done, but if xwait had just locked the tuple then * some other xact could update this tuple before we get to * this point. Check for xmax change, and start over if so. */ if ((oldtup.t_data->t_infomask & HEAP_XMAX_IS_MULTI) || !TransactionIdEquals(HeapTupleHeaderGetRawXmax(oldtup.t_data), xwait)) goto l2; /* Otherwise check if it committed or aborted */ UpdateXmaxHintBits(oldtup.t_data, buffer, xwait); if (oldtup.t_data->t_infomask & HEAP_XMAX_INVALID) can_continue = true; } } result = can_continue ? HeapTupleMayBeUpdated : HeapTupleUpdated; } if (crosscheck != InvalidSnapshot && result == HeapTupleMayBeUpdated) { /* Perform additional check for transaction-snapshot mode RI updates */ if (!HeapTupleSatisfiesVisibility(&oldtup, crosscheck, buffer)) result = HeapTupleUpdated; } if (result != HeapTupleMayBeUpdated) { Assert(result == HeapTupleSelfUpdated || result == HeapTupleUpdated || result == HeapTupleBeingUpdated); Assert(!(oldtup.t_data->t_infomask & HEAP_XMAX_INVALID)); hufd->ctid = oldtup.t_data->t_ctid; hufd->xmax = HeapTupleHeaderGetUpdateXid(oldtup.t_data); if (result == HeapTupleSelfUpdated) hufd->cmax = HeapTupleHeaderGetCmax(oldtup.t_data); else hufd->cmax = 0; /* for lack of an InvalidCommandId value */ UnlockReleaseBuffer(buffer); if (have_tuple_lock) UnlockTupleTuplock(relation, &(oldtup.t_self), *lockmode); if (vmbuffer != InvalidBuffer) ReleaseBuffer(vmbuffer); bms_free(hot_attrs); bms_free(key_attrs); return result; } /* * If we didn't pin the visibility map page and the page has become all * visible while we were busy locking the buffer, or during some * subsequent window during which we had it unlocked, we'll have to unlock * and re-lock, to avoid holding the buffer lock across an I/O. That's a * bit unfortunate, especially since we'll now have to recheck whether the * tuple has been locked or updated under us, but hopefully it won't * happen very often. */ if (vmbuffer == InvalidBuffer && PageIsAllVisible(page)) { LockBuffer(buffer, BUFFER_LOCK_UNLOCK); visibilitymap_pin(relation, block, &vmbuffer); LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE); goto l2; } /* * We're about to do the actual update -- check for conflict first, to * avoid possibly having to roll back work we've just done. */ CheckForSerializableConflictIn(relation, &oldtup, buffer); /* Fill in transaction status data */ /* * If the tuple we're updating is locked, we need to preserve the locking * info in the old tuple's Xmax. Prepare a new Xmax value for this. */ compute_new_xmax_infomask(HeapTupleHeaderGetRawXmax(oldtup.t_data), oldtup.t_data->t_infomask, oldtup.t_data->t_infomask2, xid, *lockmode, true, &xmax_old_tuple, &infomask_old_tuple, &infomask2_old_tuple); /* * And also prepare an Xmax value for the new copy of the tuple. If there * was no xmax previously, or there was one but all lockers are now gone, * then use InvalidXid; otherwise, get the xmax from the old tuple. (In * rare cases that might also be InvalidXid and yet not have the * HEAP_XMAX_INVALID bit set; that's fine.) */ if ((oldtup.t_data->t_infomask & HEAP_XMAX_INVALID) || (checked_lockers && !locker_remains)) xmax_new_tuple = InvalidTransactionId; else xmax_new_tuple = HeapTupleHeaderGetRawXmax(oldtup.t_data); if (!TransactionIdIsValid(xmax_new_tuple)) { infomask_new_tuple = HEAP_XMAX_INVALID; infomask2_new_tuple = 0; } else { /* * If we found a valid Xmax for the new tuple, then the infomask bits * to use on the new tuple depend on what was there on the old one. * Note that since we're doing an update, the only possibility is that * the lockers had FOR KEY SHARE lock. */ if (oldtup.t_data->t_infomask & HEAP_XMAX_IS_MULTI) { GetMultiXactIdHintBits(xmax_new_tuple, &infomask_new_tuple, &infomask2_new_tuple); } else { infomask_new_tuple = HEAP_XMAX_KEYSHR_LOCK | HEAP_XMAX_LOCK_ONLY; infomask2_new_tuple = 0; } } /* * Prepare the new tuple with the appropriate initial values of Xmin and * Xmax, as well as initial infomask bits as computed above. */ newtup->t_data->t_infomask &= ~(HEAP_XACT_MASK); newtup->t_data->t_infomask2 &= ~(HEAP2_XACT_MASK); HeapTupleHeaderSetXmin(newtup->t_data, xid); HeapTupleHeaderSetCmin(newtup->t_data, cid); newtup->t_data->t_infomask |= HEAP_UPDATED | infomask_new_tuple; newtup->t_data->t_infomask2 |= infomask2_new_tuple; HeapTupleHeaderSetXmax(newtup->t_data, xmax_new_tuple); /* * Replace cid with a combo cid if necessary. Note that we already put * the plain cid into the new tuple. */ HeapTupleHeaderAdjustCmax(oldtup.t_data, &cid, &iscombo); /* * If the toaster needs to be activated, OR if the new tuple will not fit * on the same page as the old, then we need to release the content lock * (but not the pin!) on the old tuple's buffer while we are off doing * TOAST and/or table-file-extension work. We must mark the old tuple to * show that it's already being updated, else other processes may try to * update it themselves. * * We need to invoke the toaster if there are already any out-of-line * toasted values present, or if the new tuple is over-threshold. */ if (relation->rd_rel->relkind != RELKIND_RELATION && relation->rd_rel->relkind != RELKIND_MATVIEW) { /* toast table entries should never be recursively toasted */ Assert(!HeapTupleHasExternal(&oldtup)); Assert(!HeapTupleHasExternal(newtup)); need_toast = false; } else need_toast = (HeapTupleHasExternal(&oldtup) || HeapTupleHasExternal(newtup) || newtup->t_len > TOAST_TUPLE_THRESHOLD); pagefree = PageGetHeapFreeSpace(page); newtupsize = MAXALIGN(newtup->t_len); if (need_toast || newtupsize > pagefree) { /* Clear obsolete visibility flags ... */ oldtup.t_data->t_infomask &= ~(HEAP_XMAX_BITS | HEAP_MOVED); oldtup.t_data->t_infomask2 &= ~HEAP_KEYS_UPDATED; HeapTupleClearHotUpdated(&oldtup); /* ... and store info about transaction updating this tuple */ Assert(TransactionIdIsValid(xmax_old_tuple)); HeapTupleHeaderSetXmax(oldtup.t_data, xmax_old_tuple); oldtup.t_data->t_infomask |= infomask_old_tuple; oldtup.t_data->t_infomask2 |= infomask2_old_tuple; HeapTupleHeaderSetCmax(oldtup.t_data, cid, iscombo); /* temporarily make it look not-updated */ oldtup.t_data->t_ctid = oldtup.t_self; already_marked = true; LockBuffer(buffer, BUFFER_LOCK_UNLOCK); /* * Let the toaster do its thing, if needed. * * Note: below this point, heaptup is the data we actually intend to * store into the relation; newtup is the caller's original untoasted * data. */ if (need_toast) { /* Note we always use WAL and FSM during updates */ heaptup = toast_insert_or_update(relation, newtup, &oldtup, 0); newtupsize = MAXALIGN(heaptup->t_len); } else heaptup = newtup; /* * Now, do we need a new page for the tuple, or not? This is a bit * tricky since someone else could have added tuples to the page while * we weren't looking. We have to recheck the available space after * reacquiring the buffer lock. But don't bother to do that if the * former amount of free space is still not enough; it's unlikely * there's more free now than before. * * What's more, if we need to get a new page, we will need to acquire * buffer locks on both old and new pages. To avoid deadlock against * some other backend trying to get the same two locks in the other * order, we must be consistent about the order we get the locks in. * We use the rule "lock the lower-numbered page of the relation * first". To implement this, we must do RelationGetBufferForTuple * while not holding the lock on the old page, and we must rely on it * to get the locks on both pages in the correct order. */ if (newtupsize > pagefree) { /* Assume there's no chance to put heaptup on same page. */ newbuf = RelationGetBufferForTuple(relation, heaptup->t_len, buffer, 0, NULL, &vmbuffer_new, &vmbuffer); } else { /* Re-acquire the lock on the old tuple's page. */ LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE); /* Re-check using the up-to-date free space */ pagefree = PageGetHeapFreeSpace(page); if (newtupsize > pagefree) { /* * Rats, it doesn't fit anymore. We must now unlock and * relock to avoid deadlock. Fortunately, this path should * seldom be taken. */ LockBuffer(buffer, BUFFER_LOCK_UNLOCK); newbuf = RelationGetBufferForTuple(relation, heaptup->t_len, buffer, 0, NULL, &vmbuffer_new, &vmbuffer); } else { /* OK, it fits here, so we're done. */ newbuf = buffer; } } } else { /* No TOAST work needed, and it'll fit on same page */ already_marked = false; newbuf = buffer; heaptup = newtup; } /* * We're about to create the new tuple -- check for conflict first, to * avoid possibly having to roll back work we've just done. * * NOTE: For a tuple insert, we only need to check for table locks, since * predicate locking at the index level will cover ranges for anything * except a table scan. Therefore, only provide the relation. */ CheckForSerializableConflictIn(relation, NULL, InvalidBuffer); /* * At this point newbuf and buffer are both pinned and locked, and newbuf * has enough space for the new tuple. If they are the same buffer, only * one pin is held. */ if (newbuf == buffer) { /* * Since the new tuple is going into the same page, we might be able * to do a HOT update. Check if any of the index columns have been * changed. If not, then HOT update is possible. */ if (satisfies_hot) use_hot_update = true; } else { /* Set a hint that the old page could use prune/defrag */ PageSetFull(page); } /* NO EREPORT(ERROR) from here till changes are logged */ START_CRIT_SECTION(); /* * If this transaction commits, the old tuple will become DEAD sooner or * later. Set flag that this page is a candidate for pruning once our xid * falls below the OldestXmin horizon. If the transaction finally aborts, * the subsequent page pruning will be a no-op and the hint will be * cleared. * * XXX Should we set hint on newbuf as well? If the transaction aborts, * there would be a prunable tuple in the newbuf; but for now we choose * not to optimize for aborts. Note that heap_xlog_update must be kept in * sync if this decision changes. */ PageSetPrunable(page, xid); if (use_hot_update) { /* Mark the old tuple as HOT-updated */ HeapTupleSetHotUpdated(&oldtup); /* And mark the new tuple as heap-only */ HeapTupleSetHeapOnly(heaptup); /* Mark the caller's copy too, in case different from heaptup */ HeapTupleSetHeapOnly(newtup); } else { /* Make sure tuples are correctly marked as not-HOT */ HeapTupleClearHotUpdated(&oldtup); HeapTupleClearHeapOnly(heaptup); HeapTupleClearHeapOnly(newtup); } RelationPutHeapTuple(relation, newbuf, heaptup); /* insert new tuple */ if (!already_marked) { /* Clear obsolete visibility flags ... */ oldtup.t_data->t_infomask &= ~(HEAP_XMAX_BITS | HEAP_MOVED); oldtup.t_data->t_infomask2 &= ~HEAP_KEYS_UPDATED; /* ... and store info about transaction updating this tuple */ Assert(TransactionIdIsValid(xmax_old_tuple)); HeapTupleHeaderSetXmax(oldtup.t_data, xmax_old_tuple); oldtup.t_data->t_infomask |= infomask_old_tuple; oldtup.t_data->t_infomask2 |= infomask2_old_tuple; HeapTupleHeaderSetCmax(oldtup.t_data, cid, iscombo); } /* record address of new tuple in t_ctid of old one */ oldtup.t_data->t_ctid = heaptup->t_self; /* clear PD_ALL_VISIBLE flags */ if (PageIsAllVisible(BufferGetPage(buffer))) { all_visible_cleared = true; PageClearAllVisible(BufferGetPage(buffer)); visibilitymap_clear(relation, BufferGetBlockNumber(buffer), vmbuffer); } if (newbuf != buffer && PageIsAllVisible(BufferGetPage(newbuf))) { all_visible_cleared_new = true; PageClearAllVisible(BufferGetPage(newbuf)); visibilitymap_clear(relation, BufferGetBlockNumber(newbuf), vmbuffer_new); } if (newbuf != buffer) MarkBufferDirty(newbuf); MarkBufferDirty(buffer); /* XLOG stuff */ if (RelationNeedsWAL(relation)) { XLogRecPtr recptr = log_heap_update(relation, buffer, newbuf, &oldtup, heaptup, all_visible_cleared, all_visible_cleared_new); if (newbuf != buffer) { PageSetLSN(BufferGetPage(newbuf), recptr); } PageSetLSN(BufferGetPage(buffer), recptr); } END_CRIT_SECTION(); if (newbuf != buffer) LockBuffer(newbuf, BUFFER_LOCK_UNLOCK); LockBuffer(buffer, BUFFER_LOCK_UNLOCK); /* * Mark old tuple for invalidation from system caches at next command * boundary, and mark the new tuple for invalidation in case we abort. We * have to do this before releasing the buffer because oldtup is in the * buffer. (heaptup is all in local memory, but it's necessary to process * both tuple versions in one call to inval.c so we can avoid redundant * sinval messages.) */ CacheInvalidateHeapTuple(relation, &oldtup, heaptup); /* Now we can release the buffer(s) */ if (newbuf != buffer) ReleaseBuffer(newbuf); ReleaseBuffer(buffer); if (BufferIsValid(vmbuffer_new)) ReleaseBuffer(vmbuffer_new); if (BufferIsValid(vmbuffer)) ReleaseBuffer(vmbuffer); /* * Release the lmgr tuple lock, if we had it. */ if (have_tuple_lock) UnlockTupleTuplock(relation, &(oldtup.t_self), *lockmode); pgstat_count_heap_update(relation, use_hot_update); /* * If heaptup is a private copy, release it. Don't forget to copy t_self * back to the caller's image, too. */ if (heaptup != newtup) { newtup->t_self = heaptup->t_self; heap_freetuple(heaptup); } bms_free(hot_attrs); bms_free(key_attrs); return HeapTupleMayBeUpdated; } /* * Check if the specified attribute's value is same in both given tuples. * Subroutine for HeapSatisfiesHOTandKeyUpdate. */ static bool heap_tuple_attr_equals(TupleDesc tupdesc, int attrnum, HeapTuple tup1, HeapTuple tup2) { Datum value1, value2; bool isnull1, isnull2; Form_pg_attribute att; /* * If it's a whole-tuple reference, say "not equal". It's not really * worth supporting this case, since it could only succeed after a no-op * update, which is hardly a case worth optimizing for. */ if (attrnum == 0) return false; /* * Likewise, automatically say "not equal" for any system attribute other * than OID and tableOID; we cannot expect these to be consistent in a HOT * chain, or even to be set correctly yet in the new tuple. */ if (attrnum < 0) { if (attrnum != ObjectIdAttributeNumber && attrnum != TableOidAttributeNumber) return false; } /* * Extract the corresponding values. XXX this is pretty inefficient if * there are many indexed columns. Should HeapSatisfiesHOTandKeyUpdate do * a single heap_deform_tuple call on each tuple, instead? But that * doesn't work for system columns ... */ value1 = heap_getattr(tup1, attrnum, tupdesc, &isnull1); value2 = heap_getattr(tup2, attrnum, tupdesc, &isnull2); /* * If one value is NULL and other is not, then they are certainly not * equal */ if (isnull1 != isnull2) return false; /* * If both are NULL, they can be considered equal. */ if (isnull1) return true; /* * We do simple binary comparison of the two datums. This may be overly * strict because there can be multiple binary representations for the * same logical value. But we should be OK as long as there are no false * positives. Using a type-specific equality operator is messy because * there could be multiple notions of equality in different operator * classes; furthermore, we cannot safely invoke user-defined functions * while holding exclusive buffer lock. */ if (attrnum <= 0) { /* The only allowed system columns are OIDs, so do this */ return (DatumGetObjectId(value1) == DatumGetObjectId(value2)); } else { Assert(attrnum <= tupdesc->natts); att = tupdesc->attrs[attrnum - 1]; return datumIsEqual(value1, value2, att->attbyval, att->attlen); } } /* * Check which columns are being updated. * * This simultaneously checks conditions for HOT updates and for FOR KEY * SHARE updates. Since much of the time they will be checking very similar * sets of columns, and doing the same tests on them, it makes sense to * optimize and do them together. * * We receive two bitmapsets comprising the two sets of columns we're * interested in. Note these are destructively modified; that is OK since * this is invoked at most once in heap_update. * * hot_result is set to TRUE if it's okay to do a HOT update (i.e. it does not * modified indexed columns); key_result is set to TRUE if the update does not * modify columns used in the key. */ static void HeapSatisfiesHOTandKeyUpdate(Relation relation, Bitmapset *hot_attrs, Bitmapset *key_attrs, bool *satisfies_hot, bool *satisfies_key, HeapTuple oldtup, HeapTuple newtup) { int next_hot_attnum; int next_key_attnum; bool hot_result = true; bool key_result = true; bool key_done = false; bool hot_done = false; next_hot_attnum = bms_first_member(hot_attrs); if (next_hot_attnum == -1) hot_done = true; else /* Adjust for system attributes */ next_hot_attnum += FirstLowInvalidHeapAttributeNumber; next_key_attnum = bms_first_member(key_attrs); if (next_key_attnum == -1) key_done = true; else /* Adjust for system attributes */ next_key_attnum += FirstLowInvalidHeapAttributeNumber; for (;;) { int check_now; bool changed; /* both bitmapsets are now empty */ if (key_done && hot_done) break; /* XXX there's probably an easier way ... */ if (hot_done) check_now = next_key_attnum; if (key_done) check_now = next_hot_attnum; else check_now = Min(next_hot_attnum, next_key_attnum); changed = !heap_tuple_attr_equals(RelationGetDescr(relation), check_now, oldtup, newtup); if (changed) { if (check_now == next_hot_attnum) hot_result = false; if (check_now == next_key_attnum) key_result = false; } /* if both are false now, we can stop checking */ if (!hot_result && !key_result) break; if (check_now == next_hot_attnum) { next_hot_attnum = bms_first_member(hot_attrs); if (next_hot_attnum == -1) hot_done = true; else /* Adjust for system attributes */ next_hot_attnum += FirstLowInvalidHeapAttributeNumber; } if (check_now == next_key_attnum) { next_key_attnum = bms_first_member(key_attrs); if (next_key_attnum == -1) key_done = true; else /* Adjust for system attributes */ next_key_attnum += FirstLowInvalidHeapAttributeNumber; } } *satisfies_hot = hot_result; *satisfies_key = key_result; } /* * simple_heap_update - replace a tuple * * This routine may be used to update a tuple when concurrent updates of * the target tuple are not expected (for example, because we have a lock * on the relation associated with the tuple). Any failure is reported * via ereport(). */ void simple_heap_update(Relation relation, ItemPointer otid, HeapTuple tup) { HTSU_Result result; HeapUpdateFailureData hufd; LockTupleMode lockmode; result = heap_update(relation, otid, tup, GetCurrentCommandId(true), InvalidSnapshot, true /* wait for commit */ , &hufd, &lockmode); switch (result) { case HeapTupleSelfUpdated: /* Tuple was already updated in current command? */ elog(ERROR, "tuple already updated by self"); break; case HeapTupleMayBeUpdated: /* done successfully */ break; case HeapTupleUpdated: elog(ERROR, "tuple concurrently updated"); break; default: elog(ERROR, "unrecognized heap_update status: %u", result); break; } } /* * Return the MultiXactStatus corresponding to the given tuple lock mode. */ static MultiXactStatus get_mxact_status_for_lock(LockTupleMode mode, bool is_update) { MultiXactStatus retval; if (is_update) retval = tupleLockExtraInfo[mode].updstatus; else retval = tupleLockExtraInfo[mode].lockstatus; if (retval == -1) elog(ERROR, "invalid lock tuple mode %d/%s", mode, is_update ? "true" : "false"); return retval; } /* * heap_lock_tuple - lock a tuple in shared or exclusive mode * * Note that this acquires a buffer pin, which the caller must release. * * Input parameters: * relation: relation containing tuple (caller must hold suitable lock) * tuple->t_self: TID of tuple to lock (rest of struct need not be valid) * cid: current command ID (used for visibility test, and stored into * tuple's cmax if lock is successful) * mode: indicates if shared or exclusive tuple lock is desired * nowait: if true, ereport rather than blocking if lock not available * follow_updates: if true, follow the update chain to also lock descendant * tuples. * * Output parameters: * *tuple: all fields filled in * *buffer: set to buffer holding tuple (pinned but not locked at exit) * *hufd: filled in failure cases (see below) * * Function result may be: * HeapTupleMayBeUpdated: lock was successfully acquired * HeapTupleSelfUpdated: lock failed because tuple updated by self * HeapTupleUpdated: lock failed because tuple updated by other xact * * In the failure cases, the routine fills *hufd with the tuple's t_ctid, * t_xmax (resolving a possible MultiXact, if necessary), and t_cmax * (the last only for HeapTupleSelfUpdated, since we * cannot obtain cmax from a combocid generated by another transaction). * See comments for struct HeapUpdateFailureData for additional info. * * See README.tuplock for a thorough explanation of this mechanism. */ HTSU_Result heap_lock_tuple(Relation relation, HeapTuple tuple, CommandId cid, LockTupleMode mode, bool nowait, bool follow_updates, Buffer *buffer, HeapUpdateFailureData *hufd) { HTSU_Result result; ItemPointer tid = &(tuple->t_self); ItemId lp; Page page; TransactionId xid, xmax; uint16 old_infomask, new_infomask, new_infomask2; bool have_tuple_lock = false; *buffer = ReadBuffer(relation, ItemPointerGetBlockNumber(tid)); LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE); page = BufferGetPage(*buffer); lp = PageGetItemId(page, ItemPointerGetOffsetNumber(tid)); Assert(ItemIdIsNormal(lp)); tuple->t_data = (HeapTupleHeader) PageGetItem(page, lp); tuple->t_len = ItemIdGetLength(lp); tuple->t_tableOid = RelationGetRelid(relation); l3: result = HeapTupleSatisfiesUpdate(tuple->t_data, cid, *buffer); if (result == HeapTupleInvisible) { UnlockReleaseBuffer(*buffer); elog(ERROR, "attempted to lock invisible tuple"); } else if (result == HeapTupleBeingUpdated) { TransactionId xwait; uint16 infomask; uint16 infomask2; bool require_sleep; ItemPointerData t_ctid; /* must copy state data before unlocking buffer */ xwait = HeapTupleHeaderGetRawXmax(tuple->t_data); infomask = tuple->t_data->t_infomask; infomask2 = tuple->t_data->t_infomask2; ItemPointerCopy(&tuple->t_data->t_ctid, &t_ctid); LockBuffer(*buffer, BUFFER_LOCK_UNLOCK); /* * If any subtransaction of the current top transaction already holds * a lock as strong or stronger than what we're requesting, we * effectively hold the desired lock already. We *must* succeed * without trying to take the tuple lock, else we will deadlock * against anyone wanting to acquire a stronger lock. */ if (infomask & HEAP_XMAX_IS_MULTI) { int i; int nmembers; MultiXactMember *members; /* * We don't need to allow old multixacts here; if that had been * the case, HeapTupleSatisfiesUpdate would have returned * MayBeUpdated and we wouldn't be here. */ nmembers = GetMultiXactIdMembers(xwait, &members, false); for (i = 0; i < nmembers; i++) { if (TransactionIdIsCurrentTransactionId(members[i].xid)) { LockTupleMode membermode; membermode = TUPLOCK_from_mxstatus(members[i].status); if (membermode >= mode) { if (have_tuple_lock) UnlockTupleTuplock(relation, tid, mode); pfree(members); return HeapTupleMayBeUpdated; } } } pfree(members); } /* * Acquire tuple lock to establish our priority for the tuple. * LockTuple will release us when we are next-in-line for the tuple. * We must do this even if we are share-locking. * * If we are forced to "start over" below, we keep the tuple lock; * this arranges that we stay at the head of the line while rechecking * tuple state. */ if (!have_tuple_lock) { if (nowait) { if (!ConditionalLockTupleTuplock(relation, tid, mode)) ereport(ERROR, (errcode(ERRCODE_LOCK_NOT_AVAILABLE), errmsg("could not obtain lock on row in relation \"%s\"", RelationGetRelationName(relation)))); } else LockTupleTuplock(relation, tid, mode); have_tuple_lock = true; } /* * Initially assume that we will have to wait for the locking * transaction(s) to finish. We check various cases below in which * this can be turned off. */ require_sleep = true; if (mode == LockTupleKeyShare) { /* * If we're requesting KeyShare, and there's no update present, we * don't need to wait. Even if there is an update, we can still * continue if the key hasn't been modified. * * However, if there are updates, we need to walk the update chain * to mark future versions of the row as locked, too. That way, * if somebody deletes that future version, we're protected * against the key going away. This locking of future versions * could block momentarily, if a concurrent transaction is * deleting a key; or it could return a value to the effect that * the transaction deleting the key has already committed. So we * do this before re-locking the buffer; otherwise this would be * prone to deadlocks. * * Note that the TID we're locking was grabbed before we unlocked * the buffer. For it to change while we're not looking, the * other properties we're testing for below after re-locking the * buffer would also change, in which case we would restart this * loop above. */ if (!(infomask2 & HEAP_KEYS_UPDATED)) { bool updated; updated = !HEAP_XMAX_IS_LOCKED_ONLY(infomask); /* * If there are updates, follow the update chain; bail out if * that cannot be done. */ if (follow_updates && updated) { HTSU_Result res; res = heap_lock_updated_tuple(relation, tuple, &t_ctid, GetCurrentTransactionId(), mode); if (res != HeapTupleMayBeUpdated) { result = res; /* recovery code expects to have buffer lock held */ LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE); goto failed; } } LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE); /* * Make sure it's still an appropriate lock, else start over. * Also, if it wasn't updated before we released the lock, but * is updated now, we start over too; the reason is that we * now need to follow the update chain to lock the new * versions. */ if (!HeapTupleHeaderIsOnlyLocked(tuple->t_data) && ((tuple->t_data->t_infomask2 & HEAP_KEYS_UPDATED) || !updated)) goto l3; /* Things look okay, so we can skip sleeping */ require_sleep = false; /* * Note we allow Xmax to change here; other updaters/lockers * could have modified it before we grabbed the buffer lock. * However, this is not a problem, because with the recheck we * just did we ensure that they still don't conflict with the * lock we want. */ } } else if (mode == LockTupleShare) { /* * If we're requesting Share, we can similarly avoid sleeping if * there's no update and no exclusive lock present. */ if (HEAP_XMAX_IS_LOCKED_ONLY(infomask) && !HEAP_XMAX_IS_EXCL_LOCKED(infomask)) { LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE); /* * Make sure it's still an appropriate lock, else start over. * See above about allowing xmax to change. */ if (!HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_data->t_infomask) || HEAP_XMAX_IS_EXCL_LOCKED(tuple->t_data->t_infomask)) goto l3; require_sleep = false; } } else if (mode == LockTupleNoKeyExclusive) { /* * If we're requesting NoKeyExclusive, we might also be able to * avoid sleeping; just ensure that there's no other lock type * than KeyShare. Note that this is a bit more involved than just * checking hint bits -- we need to expand the multixact to figure * out lock modes for each one (unless there was only one such * locker). */ if (infomask & HEAP_XMAX_IS_MULTI) { int nmembers; MultiXactMember *members; /* * We don't need to allow old multixacts here; if that had * been the case, HeapTupleSatisfiesUpdate would have returned * MayBeUpdated and we wouldn't be here. */ nmembers = GetMultiXactIdMembers(xwait, &members, false); if (nmembers <= 0) { /* * No need to keep the previous xmax here. This is * unlikely to happen. */ require_sleep = false; } else { int i; bool allowed = true; for (i = 0; i < nmembers; i++) { if (members[i].status != MultiXactStatusForKeyShare) { allowed = false; break; } } if (allowed) { /* * if the xmax changed under us in the meantime, start * over. */ LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE); if (!(tuple->t_data->t_infomask & HEAP_XMAX_IS_MULTI) || !TransactionIdEquals(HeapTupleHeaderGetRawXmax(tuple->t_data), xwait)) { pfree(members); goto l3; } /* otherwise, we're good */ require_sleep = false; } pfree(members); } } else if (HEAP_XMAX_IS_KEYSHR_LOCKED(infomask)) { LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE); /* if the xmax changed in the meantime, start over */ if ((tuple->t_data->t_infomask & HEAP_XMAX_IS_MULTI) || !TransactionIdEquals(HeapTupleHeaderGetRawXmax(tuple->t_data), xwait)) goto l3; /* otherwise, we're good */ require_sleep = false; } } /* * By here, we either have already acquired the buffer exclusive lock, * or we must wait for the locking transaction or multixact; so below * we ensure that we grab buffer lock after the sleep. */ if (require_sleep) { if (infomask & HEAP_XMAX_IS_MULTI) { MultiXactStatus status = get_mxact_status_for_lock(mode, false); /* We only ever lock tuples, never update them */ if (status >= MultiXactStatusNoKeyUpdate) elog(ERROR, "invalid lock mode in heap_lock_tuple"); /* wait for multixact to end */ if (nowait) { if (!ConditionalMultiXactIdWait((MultiXactId) xwait, status, NULL, infomask)) ereport(ERROR, (errcode(ERRCODE_LOCK_NOT_AVAILABLE), errmsg("could not obtain lock on row in relation \"%s\"", RelationGetRelationName(relation)))); } else MultiXactIdWait((MultiXactId) xwait, status, NULL, infomask); /* if there are updates, follow the update chain */ if (follow_updates && !HEAP_XMAX_IS_LOCKED_ONLY(infomask)) { HTSU_Result res; res = heap_lock_updated_tuple(relation, tuple, &t_ctid, GetCurrentTransactionId(), mode); if (res != HeapTupleMayBeUpdated) { result = res; /* recovery code expects to have buffer lock held */ LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE); goto failed; } } LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE); /* * If xwait had just locked the tuple then some other xact * could update this tuple before we get to this point. Check * for xmax change, and start over if so. */ if (!(tuple->t_data->t_infomask & HEAP_XMAX_IS_MULTI) || !TransactionIdEquals(HeapTupleHeaderGetRawXmax(tuple->t_data), xwait)) goto l3; /* * Of course, the multixact might not be done here: if we're * requesting a light lock mode, other transactions with light * locks could still be alive, as well as locks owned by our * own xact or other subxacts of this backend. We need to * preserve the surviving MultiXact members. Note that it * isn't absolutely necessary in the latter case, but doing so * is simpler. */ } else { /* wait for regular transaction to end */ if (nowait) { if (!ConditionalXactLockTableWait(xwait)) ereport(ERROR, (errcode(ERRCODE_LOCK_NOT_AVAILABLE), errmsg("could not obtain lock on row in relation \"%s\"", RelationGetRelationName(relation)))); } else XactLockTableWait(xwait); /* if there are updates, follow the update chain */ if (follow_updates && !HEAP_XMAX_IS_LOCKED_ONLY(infomask)) { HTSU_Result res; res = heap_lock_updated_tuple(relation, tuple, &t_ctid, GetCurrentTransactionId(), mode); if (res != HeapTupleMayBeUpdated) { result = res; /* recovery code expects to have buffer lock held */ LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE); goto failed; } } LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE); /* * xwait is done, but if xwait had just locked the tuple then * some other xact could update this tuple before we get to * this point. Check for xmax change, and start over if so. */ if ((tuple->t_data->t_infomask & HEAP_XMAX_IS_MULTI) || !TransactionIdEquals(HeapTupleHeaderGetRawXmax(tuple->t_data), xwait)) goto l3; /* * Otherwise check if it committed or aborted. Note we cannot * be here if the tuple was only locked by somebody who didn't * conflict with us; that should have been handled above. So * that transaction must necessarily be gone by now. */ UpdateXmaxHintBits(tuple->t_data, *buffer, xwait); } } /* By here, we're certain that we hold buffer exclusive lock again */ /* * We may lock if previous xmax aborted, or if it committed but only * locked the tuple without updating it; or if we didn't have to wait * at all for whatever reason. */ if (!require_sleep || (tuple->t_data->t_infomask & HEAP_XMAX_INVALID) || HEAP_XMAX_IS_LOCKED_ONLY(tuple->t_data->t_infomask) || HeapTupleHeaderIsOnlyLocked(tuple->t_data)) result = HeapTupleMayBeUpdated; else result = HeapTupleUpdated; } failed: if (result != HeapTupleMayBeUpdated) { Assert(result == HeapTupleSelfUpdated || result == HeapTupleUpdated); Assert(!(tuple->t_data->t_infomask & HEAP_XMAX_INVALID)); hufd->ctid = tuple->t_data->t_ctid; hufd->xmax = HeapTupleHeaderGetUpdateXid(tuple->t_data); if (result == HeapTupleSelfUpdated) hufd->cmax = HeapTupleHeaderGetCmax(tuple->t_data); else hufd->cmax = 0; /* for lack of an InvalidCommandId value */ LockBuffer(*buffer, BUFFER_LOCK_UNLOCK); if (have_tuple_lock) UnlockTupleTuplock(relation, tid, mode); return result; } xmax = HeapTupleHeaderGetRawXmax(tuple->t_data); old_infomask = tuple->t_data->t_infomask; /* * We might already hold the desired lock (or stronger), possibly under a * different subtransaction of the current top transaction. If so, there * is no need to change state or issue a WAL record. We already handled * the case where this is true for xmax being a MultiXactId, so now check * for cases where it is a plain TransactionId. * * Note in particular that this covers the case where we already hold * exclusive lock on the tuple and the caller only wants key share or * share lock. It would certainly not do to give up the exclusive lock. */ if (!(old_infomask & (HEAP_XMAX_INVALID | HEAP_XMAX_COMMITTED | HEAP_XMAX_IS_MULTI)) && (mode == LockTupleKeyShare ? (HEAP_XMAX_IS_KEYSHR_LOCKED(old_infomask) || HEAP_XMAX_IS_SHR_LOCKED(old_infomask) || HEAP_XMAX_IS_EXCL_LOCKED(old_infomask)) : mode == LockTupleShare ? (HEAP_XMAX_IS_SHR_LOCKED(old_infomask) || HEAP_XMAX_IS_EXCL_LOCKED(old_infomask)) : (HEAP_XMAX_IS_EXCL_LOCKED(old_infomask))) && TransactionIdIsCurrentTransactionId(xmax)) { LockBuffer(*buffer, BUFFER_LOCK_UNLOCK); /* Probably can't hold tuple lock here, but may as well check */ if (have_tuple_lock) UnlockTupleTuplock(relation, tid, mode); return HeapTupleMayBeUpdated; } /* * If this is the first possibly-multixact-able operation in the current * transaction, set my per-backend OldestMemberMXactId setting. We can be * certain that the transaction will never become a member of any older * MultiXactIds than that. (We have to do this even if we end up just * using our own TransactionId below, since some other backend could * incorporate our XID into a MultiXact immediately afterwards.) */ MultiXactIdSetOldestMember(); /* * Compute the new xmax and infomask to store into the tuple. Note we do * not modify the tuple just yet, because that would leave it in the wrong * state if multixact.c elogs. */ compute_new_xmax_infomask(xmax, old_infomask, tuple->t_data->t_infomask2, GetCurrentTransactionId(), mode, false, &xid, &new_infomask, &new_infomask2); START_CRIT_SECTION(); /* * Store transaction information of xact locking the tuple. * * Note: Cmax is meaningless in this context, so don't set it; this avoids * possibly generating a useless combo CID. Moreover, if we're locking a * previously updated tuple, it's important to preserve the Cmax. * * Also reset the HOT UPDATE bit, but only if there's no update; otherwise * we would break the HOT chain. */ tuple->t_data->t_infomask &= ~HEAP_XMAX_BITS; tuple->t_data->t_infomask2 &= ~HEAP_KEYS_UPDATED; tuple->t_data->t_infomask |= new_infomask; tuple->t_data->t_infomask2 |= new_infomask2; if (HEAP_XMAX_IS_LOCKED_ONLY(new_infomask)) HeapTupleHeaderClearHotUpdated(tuple->t_data); HeapTupleHeaderSetXmax(tuple->t_data, xid); /* * Make sure there is no forward chain link in t_ctid. Note that in the * cases where the tuple has been updated, we must not overwrite t_ctid, * because it was set by the updater. Moreover, if the tuple has been * updated, we need to follow the update chain to lock the new versions of * the tuple as well. */ if (HEAP_XMAX_IS_LOCKED_ONLY(new_infomask)) tuple->t_data->t_ctid = *tid; MarkBufferDirty(*buffer); /* * XLOG stuff. You might think that we don't need an XLOG record because * there is no state change worth restoring after a crash. You would be * wrong however: we have just written either a TransactionId or a * MultiXactId that may never have been seen on disk before, and we need * to make sure that there are XLOG entries covering those ID numbers. * Else the same IDs might be re-used after a crash, which would be * disastrous if this page made it to disk before the crash. Essentially * we have to enforce the WAL log-before-data rule even in this case. * (Also, in a PITR log-shipping or 2PC environment, we have to have XLOG * entries for everything anyway.) */ if (RelationNeedsWAL(relation)) { xl_heap_lock xlrec; XLogRecPtr recptr; XLogRecData rdata[2]; xlrec.target.node = relation->rd_node; xlrec.target.tid = tuple->t_self; xlrec.locking_xid = xid; xlrec.infobits_set = compute_infobits(new_infomask, tuple->t_data->t_infomask2); rdata[0].data = (char *) &xlrec; rdata[0].len = SizeOfHeapLock; rdata[0].buffer = InvalidBuffer; rdata[0].next = &(rdata[1]); rdata[1].data = NULL; rdata[1].len = 0; rdata[1].buffer = *buffer; rdata[1].buffer_std = true; rdata[1].next = NULL; recptr = XLogInsert(RM_HEAP_ID, XLOG_HEAP_LOCK, rdata); PageSetLSN(page, recptr); } END_CRIT_SECTION(); LockBuffer(*buffer, BUFFER_LOCK_UNLOCK); /* * Don't update the visibility map here. Locking a tuple doesn't change * visibility info. */ /* * Now that we have successfully marked the tuple as locked, we can * release the lmgr tuple lock, if we had it. */ if (have_tuple_lock) UnlockTupleTuplock(relation, tid, mode); return HeapTupleMayBeUpdated; } /* * Given an original set of Xmax and infomask, and a transaction (identified by * add_to_xmax) acquiring a new lock of some mode, compute the new Xmax and * corresponding infomasks to use on the tuple. * * Note that this might have side effects such as creating a new MultiXactId. * * Most callers will have called HeapTupleSatisfiesUpdate before this function; * that will have set the HEAP_XMAX_INVALID bit if the xmax was a MultiXactId * but it was not running anymore. There is a race condition, which is that the * MultiXactId may have finished since then, but that uncommon case is handled * either here, or within MultiXactIdExpand. * * There is a similar race condition possible when the old xmax was a regular * TransactionId. We test TransactionIdIsInProgress again just to narrow the * window, but it's still possible to end up creating an unnecessary * MultiXactId. Fortunately this is harmless. */ static void compute_new_xmax_infomask(TransactionId xmax, uint16 old_infomask, uint16 old_infomask2, TransactionId add_to_xmax, LockTupleMode mode, bool is_update, TransactionId *result_xmax, uint16 *result_infomask, uint16 *result_infomask2) { TransactionId new_xmax; uint16 new_infomask, new_infomask2; l5: new_infomask = 0; new_infomask2 = 0; if (old_infomask & HEAP_XMAX_INVALID) { /* * No previous locker; we just insert our own TransactionId. */ if (is_update) { new_xmax = add_to_xmax; if (mode == LockTupleExclusive) new_infomask2 |= HEAP_KEYS_UPDATED; } else { new_infomask |= HEAP_XMAX_LOCK_ONLY; switch (mode) { case LockTupleKeyShare: new_xmax = add_to_xmax; new_infomask |= HEAP_XMAX_KEYSHR_LOCK; break; case LockTupleShare: new_xmax = add_to_xmax; new_infomask |= HEAP_XMAX_SHR_LOCK; break; case LockTupleNoKeyExclusive: new_xmax = add_to_xmax; new_infomask |= HEAP_XMAX_EXCL_LOCK; break; case LockTupleExclusive: new_xmax = add_to_xmax; new_infomask |= HEAP_XMAX_EXCL_LOCK; new_infomask2 |= HEAP_KEYS_UPDATED; break; default: new_xmax = InvalidTransactionId; /* silence compiler */ elog(ERROR, "invalid lock mode"); } } } else if (old_infomask & HEAP_XMAX_IS_MULTI) { MultiXactStatus new_status; /* * Currently we don't allow XMAX_COMMITTED to be set for multis, so * cross-check. */ Assert(!(old_infomask & HEAP_XMAX_COMMITTED)); /* * A multixact together with LOCK_ONLY set but neither lock bit set * (i.e. a pg_upgraded share locked tuple) cannot possibly be running * anymore. This check is critical for databases upgraded by * pg_upgrade; both MultiXactIdIsRunning and MultiXactIdExpand assume * that such multis are never passed. */ if (!(old_infomask & HEAP_LOCK_MASK) && HEAP_XMAX_IS_LOCKED_ONLY(old_infomask)) { old_infomask &= ~HEAP_XMAX_IS_MULTI; old_infomask |= HEAP_XMAX_INVALID; goto l5; } /* * If the XMAX is already a MultiXactId, then we need to expand it to * include add_to_xmax; but if all the members were lockers and are * all gone, we can do away with the IS_MULTI bit and just set * add_to_xmax as the only locker/updater. If all lockers are gone * and we have an updater that aborted, we can also do without a * multi. * * The cost of doing GetMultiXactIdMembers would be paid by * MultiXactIdExpand if we weren't to do this, so this check is not * incurring extra work anyhow. */ if (!MultiXactIdIsRunning(xmax)) { if (HEAP_XMAX_IS_LOCKED_ONLY(old_infomask) || TransactionIdDidAbort(MultiXactIdGetUpdateXid(xmax, old_infomask))) { /* * Reset these bits and restart; otherwise fall through to * create a new multi below. */ old_infomask &= ~HEAP_XMAX_IS_MULTI; old_infomask |= HEAP_XMAX_INVALID; goto l5; } } new_status = get_mxact_status_for_lock(mode, is_update); new_xmax = MultiXactIdExpand((MultiXactId) xmax, add_to_xmax, new_status); GetMultiXactIdHintBits(new_xmax, &new_infomask, &new_infomask2); } else if (old_infomask & HEAP_XMAX_COMMITTED) { /* * It's a committed update, so we need to preserve him as updater of * the tuple. */ MultiXactStatus status; MultiXactStatus new_status; if (old_infomask2 & HEAP_KEYS_UPDATED) status = MultiXactStatusUpdate; else status = MultiXactStatusNoKeyUpdate; new_status = get_mxact_status_for_lock(mode, is_update); /* * since it's not running, it's obviously impossible for the old * updater to be identical to the current one, so we need not check * for that case as we do in the block above. */ new_xmax = MultiXactIdCreate(xmax, status, add_to_xmax, new_status); GetMultiXactIdHintBits(new_xmax, &new_infomask, &new_infomask2); } else if (TransactionIdIsInProgress(xmax)) { /* * If the XMAX is a valid, in-progress TransactionId, then we need to * create a new MultiXactId that includes both the old locker or * updater and our own TransactionId. */ MultiXactStatus status; MultiXactStatus new_status; if (HEAP_XMAX_IS_LOCKED_ONLY(old_infomask)) { if (HEAP_XMAX_IS_KEYSHR_LOCKED(old_infomask)) status = MultiXactStatusForKeyShare; else if (HEAP_XMAX_IS_SHR_LOCKED(old_infomask)) status = MultiXactStatusForShare; else if (HEAP_XMAX_IS_EXCL_LOCKED(old_infomask)) { if (old_infomask2 & HEAP_KEYS_UPDATED) status = MultiXactStatusForUpdate; else status = MultiXactStatusForNoKeyUpdate; } else { /* * LOCK_ONLY can be present alone only when a page has been * upgraded by pg_upgrade. But in that case, * TransactionIdIsInProgress() should have returned false. We * assume it's no longer locked in this case. */ elog(WARNING, "LOCK_ONLY found for Xid in progress %u", xmax); old_infomask |= HEAP_XMAX_INVALID; old_infomask &= ~HEAP_XMAX_LOCK_ONLY; goto l5; } } else { /* it's an update, but which kind? */ if (old_infomask2 & HEAP_KEYS_UPDATED) status = MultiXactStatusUpdate; else status = MultiXactStatusNoKeyUpdate; } new_status = get_mxact_status_for_lock(mode, is_update); /* * If the existing lock mode is identical to or weaker than the new * one, we can act as though there is no existing lock, so set * XMAX_INVALID and restart. */ if (xmax == add_to_xmax) { LockTupleMode old_mode = TUPLOCK_from_mxstatus(status); bool old_isupd = ISUPDATE_from_mxstatus(status); /* * We can do this if the new LockTupleMode is higher or equal than * the old one; and if there was previously an update, we need an * update, but if there wasn't, then we can accept there not being * one. */ if ((mode >= old_mode) && (is_update || !old_isupd)) { /* * Note that the infomask might contain some other dirty bits. * However, since the new infomask is reset to zero, we only * set what's minimally necessary, and that the case that * checks HEAP_XMAX_INVALID is the very first above, there is * no need for extra cleanup of the infomask here. */ old_infomask |= HEAP_XMAX_INVALID; goto l5; } } new_xmax = MultiXactIdCreate(xmax, status, add_to_xmax, new_status); GetMultiXactIdHintBits(new_xmax, &new_infomask, &new_infomask2); } else if (!HEAP_XMAX_IS_LOCKED_ONLY(old_infomask) && TransactionIdDidCommit(xmax)) { /* * It's a committed update, so we gotta preserve him as updater of the * tuple. */ MultiXactStatus status; MultiXactStatus new_status; if (old_infomask2 & HEAP_KEYS_UPDATED) status = MultiXactStatusUpdate; else status = MultiXactStatusNoKeyUpdate; new_status = get_mxact_status_for_lock(mode, is_update); /* * since it's not running, it's obviously impossible for the old * updater to be identical to the current one, so we need not check * for that case as we do in the block above. */ new_xmax = MultiXactIdCreate(xmax, status, add_to_xmax, new_status); GetMultiXactIdHintBits(new_xmax, &new_infomask, &new_infomask2); } else { /* * Can get here iff the locking/updating transaction was running when * the infomask was extracted from the tuple, but finished before * TransactionIdIsInProgress got to run. Deal with it as if there was * no locker at all in the first place. */ old_infomask |= HEAP_XMAX_INVALID; goto l5; } *result_infomask = new_infomask; *result_infomask2 = new_infomask2; *result_xmax = new_xmax; } /* * Recursive part of heap_lock_updated_tuple * * Fetch the tuple pointed to by tid in rel, and mark it as locked by the given * xid with the given mode; if this tuple is updated, recurse to lock the new * version as well. */ static HTSU_Result heap_lock_updated_tuple_rec(Relation rel, ItemPointer tid, TransactionId xid, LockTupleMode mode) { ItemPointerData tupid; HeapTupleData mytup; Buffer buf; uint16 new_infomask, new_infomask2, old_infomask; TransactionId xmax, new_xmax; ItemPointerCopy(tid, &tupid); for (;;) { new_infomask = 0; new_xmax = InvalidTransactionId; ItemPointerCopy(&tupid, &(mytup.t_self)); if (!heap_fetch(rel, SnapshotAny, &mytup, &buf, false, NULL)) elog(ERROR, "unable to fetch updated version of tuple"); l4: CHECK_FOR_INTERRUPTS(); LockBuffer(buf, BUFFER_LOCK_EXCLUSIVE); old_infomask = mytup.t_data->t_infomask; xmax = HeapTupleHeaderGetRawXmax(mytup.t_data); /* * If this tuple is updated and the key has been modified (or * deleted), what we do depends on the status of the updating * transaction: if it's live, we sleep until it finishes; if it has * committed, we have to fail (i.e. return HeapTupleUpdated); if it * aborted, we ignore it. For updates that didn't touch the key, we * can just plough ahead. */ if (!(old_infomask & HEAP_XMAX_INVALID) && (mytup.t_data->t_infomask2 & HEAP_KEYS_UPDATED)) { TransactionId update_xid; /* * Note: we *must* check TransactionIdIsInProgress before * TransactionIdDidAbort/Commit; see comment at top of tqual.c for * an explanation. */ update_xid = HeapTupleHeaderGetUpdateXid(mytup.t_data); if (TransactionIdIsCurrentTransactionId(update_xid)) { UnlockReleaseBuffer(buf); return HeapTupleSelfUpdated; } else if (TransactionIdIsInProgress(update_xid)) { LockBuffer(buf, BUFFER_LOCK_UNLOCK); /* No LockTupleTuplock here -- see heap_lock_updated_tuple */ XactLockTableWait(update_xid); goto l4; } else if (TransactionIdDidAbort(update_xid)) ; /* okay to proceed */ else if (TransactionIdDidCommit(update_xid)) { UnlockReleaseBuffer(buf); return HeapTupleUpdated; } } /* compute the new Xmax and infomask values for the tuple ... */ compute_new_xmax_infomask(xmax, old_infomask, mytup.t_data->t_infomask2, xid, mode, false, &new_xmax, &new_infomask, &new_infomask2); START_CRIT_SECTION(); /* ... and set them */ HeapTupleHeaderSetXmax(mytup.t_data, new_xmax); mytup.t_data->t_infomask &= ~HEAP_XMAX_BITS; mytup.t_data->t_infomask2 &= ~HEAP_KEYS_UPDATED; mytup.t_data->t_infomask |= new_infomask; mytup.t_data->t_infomask2 |= new_infomask2; MarkBufferDirty(buf); /* XLOG stuff */ if (RelationNeedsWAL(rel)) { xl_heap_lock_updated xlrec; XLogRecPtr recptr; XLogRecData rdata[2]; Page page = BufferGetPage(buf); xlrec.target.node = rel->rd_node; xlrec.target.tid = mytup.t_self; xlrec.xmax = new_xmax; xlrec.infobits_set = compute_infobits(new_infomask, new_infomask2); rdata[0].data = (char *) &xlrec; rdata[0].len = SizeOfHeapLockUpdated; rdata[0].buffer = InvalidBuffer; rdata[0].next = &(rdata[1]); rdata[1].data = NULL; rdata[1].len = 0; rdata[1].buffer = buf; rdata[1].buffer_std = true; rdata[1].next = NULL; recptr = XLogInsert(RM_HEAP2_ID, XLOG_HEAP2_LOCK_UPDATED, rdata); PageSetLSN(page, recptr); } END_CRIT_SECTION(); /* if we find the end of update chain, we're done. */ if (mytup.t_data->t_infomask & HEAP_XMAX_INVALID || ItemPointerEquals(&mytup.t_self, &mytup.t_data->t_ctid) || HeapTupleHeaderIsOnlyLocked(mytup.t_data)) { UnlockReleaseBuffer(buf); return HeapTupleMayBeUpdated; } /* tail recursion */ ItemPointerCopy(&(mytup.t_data->t_ctid), &tupid); UnlockReleaseBuffer(buf); } } /* * heap_lock_updated_tuple * Follow update chain when locking an updated tuple, acquiring locks (row * marks) on the updated versions. * * The initial tuple is assumed to be already locked. * * This function doesn't check visibility, it just inconditionally marks the * tuple(s) as locked. If any tuple in the updated chain is being deleted * concurrently (or updated with the key being modified), sleep until the * transaction doing it is finished. * * Note that we don't acquire heavyweight tuple locks on the tuples we walk * when we have to wait for other transactions to release them, as opposed to * what heap_lock_tuple does. The reason is that having more than one * transaction walking the chain is probably uncommon enough that risk of * starvation is not likely: one of the preconditions for being here is that * the snapshot in use predates the update that created this tuple (because we * started at an earlier version of the tuple), but at the same time such a * transaction cannot be using repeatable read or serializable isolation * levels, because that would lead to a serializability failure. */ static HTSU_Result heap_lock_updated_tuple(Relation rel, HeapTuple tuple, ItemPointer ctid, TransactionId xid, LockTupleMode mode) { if (!ItemPointerEquals(&tuple->t_self, ctid)) { /* * If this is the first possibly-multixact-able operation in the * current transaction, set my per-backend OldestMemberMXactId * setting. We can be certain that the transaction will never become a * member of any older MultiXactIds than that. (We have to do this * even if we end up just using our own TransactionId below, since * some other backend could incorporate our XID into a MultiXact * immediately afterwards.) */ MultiXactIdSetOldestMember(); return heap_lock_updated_tuple_rec(rel, ctid, xid, mode); } /* nothing to lock */ return HeapTupleMayBeUpdated; } /* * heap_inplace_update - update a tuple "in place" (ie, overwrite it) * * Overwriting violates both MVCC and transactional safety, so the uses * of this function in Postgres are extremely limited. Nonetheless we * find some places to use it. * * The tuple cannot change size, and therefore it's reasonable to assume * that its null bitmap (if any) doesn't change either. So we just * overwrite the data portion of the tuple without touching the null * bitmap or any of the header fields. * * tuple is an in-memory tuple structure containing the data to be written * over the target tuple. Also, tuple->t_self identifies the target tuple. */ void heap_inplace_update(Relation relation, HeapTuple tuple) { Buffer buffer; Page page; OffsetNumber offnum; ItemId lp = NULL; HeapTupleHeader htup; uint32 oldlen; uint32 newlen; buffer = ReadBuffer(relation, ItemPointerGetBlockNumber(&(tuple->t_self))); LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE); page = (Page) BufferGetPage(buffer); offnum = ItemPointerGetOffsetNumber(&(tuple->t_self)); if (PageGetMaxOffsetNumber(page) >= offnum) lp = PageGetItemId(page, offnum); if (PageGetMaxOffsetNumber(page) < offnum || !ItemIdIsNormal(lp)) elog(ERROR, "heap_inplace_update: invalid lp"); htup = (HeapTupleHeader) PageGetItem(page, lp); oldlen = ItemIdGetLength(lp) - htup->t_hoff; newlen = tuple->t_len - tuple->t_data->t_hoff; if (oldlen != newlen || htup->t_hoff != tuple->t_data->t_hoff) elog(ERROR, "heap_inplace_update: wrong tuple length"); /* NO EREPORT(ERROR) from here till changes are logged */ START_CRIT_SECTION(); memcpy((char *) htup + htup->t_hoff, (char *) tuple->t_data + tuple->t_data->t_hoff, newlen); MarkBufferDirty(buffer); /* XLOG stuff */ if (RelationNeedsWAL(relation)) { xl_heap_inplace xlrec; XLogRecPtr recptr; XLogRecData rdata[2]; xlrec.target.node = relation->rd_node; xlrec.target.tid = tuple->t_self; rdata[0].data = (char *) &xlrec; rdata[0].len = SizeOfHeapInplace; rdata[0].buffer = InvalidBuffer; rdata[0].next = &(rdata[1]); rdata[1].data = (char *) htup + htup->t_hoff; rdata[1].len = newlen; rdata[1].buffer = buffer; rdata[1].buffer_std = true; rdata[1].next = NULL; recptr = XLogInsert(RM_HEAP_ID, XLOG_HEAP_INPLACE, rdata); PageSetLSN(page, recptr); } END_CRIT_SECTION(); UnlockReleaseBuffer(buffer); /* * Send out shared cache inval if necessary. Note that because we only * pass the new version of the tuple, this mustn't be used for any * operations that could change catcache lookup keys. But we aren't * bothering with index updates either, so that's true a fortiori. */ if (!IsBootstrapProcessingMode()) CacheInvalidateHeapTuple(relation, tuple, NULL); } /* * heap_freeze_tuple * * Check to see whether any of the XID fields of a tuple (xmin, xmax, xvac) * are older than the specified cutoff XID. If so, replace them with * FrozenTransactionId or InvalidTransactionId as appropriate, and return * TRUE. Return FALSE if nothing was changed. * * It is assumed that the caller has checked the tuple with * HeapTupleSatisfiesVacuum() and determined that it is not HEAPTUPLE_DEAD * (else we should be removing the tuple, not freezing it). * * NB: cutoff_xid *must* be <= the current global xmin, to ensure that any * XID older than it could neither be running nor seen as running by any * open transaction. This ensures that the replacement will not change * anyone's idea of the tuple state. Also, since we assume the tuple is * not HEAPTUPLE_DEAD, the fact that an XID is not still running allows us * to assume that it is either committed good or aborted, as appropriate; * so we need no external state checks to decide what to do. (This is good * because this function is applied during WAL recovery, when we don't have * access to any such state, and can't depend on the hint bits to be set.) * * Similarly, cutoff_multi must be less than or equal to the smallest * MultiXactId used by any transaction currently open. * * If the tuple is in a shared buffer, caller must hold an exclusive lock on * that buffer. * * Note: it might seem we could make the changes without exclusive lock, since * TransactionId read/write is assumed atomic anyway. However there is a race * condition: someone who just fetched an old XID that we overwrite here could * conceivably not finish checking the XID against pg_clog before we finish * the VACUUM and perhaps truncate off the part of pg_clog he needs. Getting * exclusive lock ensures no other backend is in process of checking the * tuple status. Also, getting exclusive lock makes it safe to adjust the * infomask bits. */ bool heap_freeze_tuple(HeapTupleHeader tuple, TransactionId cutoff_xid, MultiXactId cutoff_multi) { bool changed = false; TransactionId xid; xid = HeapTupleHeaderGetXmin(tuple); if (TransactionIdIsNormal(xid) && TransactionIdPrecedes(xid, cutoff_xid)) { HeapTupleHeaderSetXmin(tuple, FrozenTransactionId); /* * Might as well fix the hint bits too; usually XMIN_COMMITTED will * already be set here, but there's a small chance not. */ Assert(!(tuple->t_infomask & HEAP_XMIN_INVALID)); tuple->t_infomask |= HEAP_XMIN_COMMITTED; changed = true; } /* * Note that this code handles IS_MULTI Xmax values, too, but only to mark * the tuple frozen if the updating Xid in the mxact is below the freeze * cutoff; it doesn't remove dead members of a very old multixact. */ xid = HeapTupleHeaderGetRawXmax(tuple); if ((tuple->t_infomask & HEAP_XMAX_IS_MULTI) ? (MultiXactIdIsValid(xid) && MultiXactIdPrecedes(xid, cutoff_multi)) : (TransactionIdIsNormal(xid) && TransactionIdPrecedes(xid, cutoff_xid))) { HeapTupleHeaderSetXmax(tuple, InvalidTransactionId); /* * The tuple might be marked either XMAX_INVALID or XMAX_COMMITTED + * LOCKED. Normalize to INVALID just to be sure no one gets confused. * Also get rid of the HEAP_KEYS_UPDATED bit. */ tuple->t_infomask &= ~HEAP_XMAX_BITS; tuple->t_infomask |= HEAP_XMAX_INVALID; HeapTupleHeaderClearHotUpdated(tuple); tuple->t_infomask2 &= ~HEAP_KEYS_UPDATED; changed = true; } /* * Old-style VACUUM FULL is gone, but we have to keep this code as long as * we support having MOVED_OFF/MOVED_IN tuples in the database. */ if (tuple->t_infomask & HEAP_MOVED) { xid = HeapTupleHeaderGetXvac(tuple); if (TransactionIdIsNormal(xid) && TransactionIdPrecedes(xid, cutoff_xid)) { /* * If a MOVED_OFF tuple is not dead, the xvac transaction must * have failed; whereas a non-dead MOVED_IN tuple must mean the * xvac transaction succeeded. */ if (tuple->t_infomask & HEAP_MOVED_OFF) HeapTupleHeaderSetXvac(tuple, InvalidTransactionId); else HeapTupleHeaderSetXvac(tuple, FrozenTransactionId); /* * Might as well fix the hint bits too; usually XMIN_COMMITTED * will already be set here, but there's a small chance not. */ Assert(!(tuple->t_infomask & HEAP_XMIN_INVALID)); tuple->t_infomask |= HEAP_XMIN_COMMITTED; changed = true; } } return changed; } /* * For a given MultiXactId, return the hint bits that should be set in the * tuple's infomask. * * Normally this should be called for a multixact that was just created, and * so is on our local cache, so the GetMembers call is fast. */ static void GetMultiXactIdHintBits(MultiXactId multi, uint16 *new_infomask, uint16 *new_infomask2) { int nmembers; MultiXactMember *members; int i; uint16 bits = HEAP_XMAX_IS_MULTI; uint16 bits2 = 0; bool has_update = false; LockTupleMode strongest = LockTupleKeyShare; /* * We only use this in multis we just created, so they cannot be values * pre-pg_upgrade. */ nmembers = GetMultiXactIdMembers(multi, &members, false); for (i = 0; i < nmembers; i++) { LockTupleMode mode; /* * Remember the strongest lock mode held by any member of the * multixact. */ mode = TUPLOCK_from_mxstatus(members[i].status); if (mode > strongest) strongest = mode; /* See what other bits we need */ switch (members[i].status) { case MultiXactStatusForKeyShare: case MultiXactStatusForShare: case MultiXactStatusForNoKeyUpdate: break; case MultiXactStatusForUpdate: bits2 |= HEAP_KEYS_UPDATED; break; case MultiXactStatusNoKeyUpdate: has_update = true; break; case MultiXactStatusUpdate: bits2 |= HEAP_KEYS_UPDATED; has_update = true; break; } } if (strongest == LockTupleExclusive || strongest == LockTupleNoKeyExclusive) bits |= HEAP_XMAX_EXCL_LOCK; else if (strongest == LockTupleShare) bits |= HEAP_XMAX_SHR_LOCK; else if (strongest == LockTupleKeyShare) bits |= HEAP_XMAX_KEYSHR_LOCK; if (!has_update) bits |= HEAP_XMAX_LOCK_ONLY; if (nmembers > 0) pfree(members); *new_infomask = bits; *new_infomask2 = bits2; } /* * MultiXactIdGetUpdateXid * * Given a multixact Xmax and corresponding infomask, which does not have the * HEAP_XMAX_LOCK_ONLY bit set, obtain and return the Xid of the updating * transaction. */ static TransactionId MultiXactIdGetUpdateXid(TransactionId xmax, uint16 t_infomask) { TransactionId update_xact = InvalidTransactionId; MultiXactMember *members; int nmembers; Assert(!(t_infomask & HEAP_XMAX_LOCK_ONLY)); Assert(t_infomask & HEAP_XMAX_IS_MULTI); /* * Since we know the LOCK_ONLY bit is not set, this cannot be a multi from * pre-pg_upgrade. */ nmembers = GetMultiXactIdMembers(xmax, &members, false); if (nmembers > 0) { int i; for (i = 0; i < nmembers; i++) { /* Ignore lockers */ if (members[i].status == MultiXactStatusForKeyShare || members[i].status == MultiXactStatusForShare || members[i].status == MultiXactStatusForNoKeyUpdate || members[i].status == MultiXactStatusForUpdate) continue; /* ignore aborted transactions */ if (TransactionIdDidAbort(members[i].xid)) continue; /* there should be at most one non-aborted updater */ Assert(update_xact == InvalidTransactionId); Assert(members[i].status == MultiXactStatusNoKeyUpdate || members[i].status == MultiXactStatusUpdate); update_xact = members[i].xid; #ifndef USE_ASSERT_CHECKING /* * in an assert-enabled build, walk the whole array to ensure * there's no other updater. */ break; #endif } pfree(members); } return update_xact; } /* * HeapTupleGetUpdateXid * As above, but use a HeapTupleHeader * * See also HeapTupleHeaderGetUpdateXid, which can be used without previously * checking the hint bits. */ TransactionId HeapTupleGetUpdateXid(HeapTupleHeader tuple) { return MultiXactIdGetUpdateXid(HeapTupleHeaderGetRawXmax(tuple), tuple->t_infomask); } /* * Do_MultiXactIdWait * Actual implementation for the two functions below. * * We do this by sleeping on each member using XactLockTableWait. Any * members that belong to the current backend are *not* waited for, however; * this would not merely be useless but would lead to Assert failure inside * XactLockTableWait. By the time this returns, it is certain that all * transactions *of other backends* that were members of the MultiXactId * that conflict with the requested status are dead (and no new ones can have * been added, since it is not legal to add members to an existing * MultiXactId). * * But by the time we finish sleeping, someone else may have changed the Xmax * of the containing tuple, so the caller needs to iterate on us somehow. * * Note that in case we return false, the number of remaining members is * not to be trusted. */ static bool Do_MultiXactIdWait(MultiXactId multi, MultiXactStatus status, int *remaining, uint16 infomask, bool nowait) { bool allow_old; bool result = true; MultiXactMember *members; int nmembers; int remain = 0; allow_old = !(infomask & HEAP_LOCK_MASK) && HEAP_XMAX_IS_LOCKED_ONLY(infomask); nmembers = GetMultiXactIdMembers(multi, &members, allow_old); if (nmembers >= 0) { int i; for (i = 0; i < nmembers; i++) { TransactionId memxid = members[i].xid; MultiXactStatus memstatus = members[i].status; if (TransactionIdIsCurrentTransactionId(memxid)) { remain++; continue; } if (!DoLockModesConflict(LOCKMODE_from_mxstatus(memstatus), LOCKMODE_from_mxstatus(status))) { if (remaining && TransactionIdIsInProgress(memxid)) remain++; continue; } /* * This member conflicts with our multi, so we have to sleep (or * return failure, if asked to avoid waiting.) */ if (nowait) { result = ConditionalXactLockTableWait(memxid); if (!result) break; } else XactLockTableWait(memxid); } pfree(members); } if (remaining) *remaining = remain; return result; } /* * MultiXactIdWait * Sleep on a MultiXactId. * * By the time we finish sleeping, someone else may have changed the Xmax * of the containing tuple, so the caller needs to iterate on us somehow. * * We return (in *remaining, if not NULL) the number of members that are still * running, including any (non-aborted) subtransactions of our own transaction. * */ static void MultiXactIdWait(MultiXactId multi, MultiXactStatus status, int *remaining, uint16 infomask) { Do_MultiXactIdWait(multi, status, remaining, infomask, false); } /* * ConditionalMultiXactIdWait * As above, but only lock if we can get the lock without blocking. * * By the time we finish sleeping, someone else may have changed the Xmax * of the containing tuple, so the caller needs to iterate on us somehow. * * If the multixact is now all gone, return true. Returns false if some * transactions might still be running. * * We return (in *remaining, if not NULL) the number of members that are still * running, including any (non-aborted) subtransactions of our own transaction. */ static bool ConditionalMultiXactIdWait(MultiXactId multi, MultiXactStatus status, int *remaining, uint16 infomask) { return Do_MultiXactIdWait(multi, status, remaining, infomask, true); } /* * heap_tuple_needs_freeze * * Check to see whether any of the XID fields of a tuple (xmin, xmax, xvac) * are older than the specified cutoff XID or MultiXactId. If so, return TRUE. * * It doesn't matter whether the tuple is alive or dead, we are checking * to see if a tuple needs to be removed or frozen to avoid wraparound. */ bool heap_tuple_needs_freeze(HeapTupleHeader tuple, TransactionId cutoff_xid, MultiXactId cutoff_multi, Buffer buf) { TransactionId xid; xid = HeapTupleHeaderGetXmin(tuple); if (TransactionIdIsNormal(xid) && TransactionIdPrecedes(xid, cutoff_xid)) return true; if (!(tuple->t_infomask & HEAP_XMAX_INVALID)) { if (!(tuple->t_infomask & HEAP_XMAX_IS_MULTI)) { xid = HeapTupleHeaderGetRawXmax(tuple); if (TransactionIdIsNormal(xid) && TransactionIdPrecedes(xid, cutoff_xid)) return true; } else { MultiXactId multi; multi = HeapTupleHeaderGetRawXmax(tuple); if (MultiXactIdPrecedes(multi, cutoff_multi)) return true; } } if (tuple->t_infomask & HEAP_MOVED) { xid = HeapTupleHeaderGetXvac(tuple); if (TransactionIdIsNormal(xid) && TransactionIdPrecedes(xid, cutoff_xid)) return true; } return false; } /* ---------------- * heap_markpos - mark scan position * ---------------- */ void heap_markpos(HeapScanDesc scan) { /* Note: no locking manipulations needed */ if (scan->rs_ctup.t_data != NULL) { scan->rs_mctid = scan->rs_ctup.t_self; if (scan->rs_pageatatime) scan->rs_mindex = scan->rs_cindex; } else ItemPointerSetInvalid(&scan->rs_mctid); } /* ---------------- * heap_restrpos - restore position to marked location * ---------------- */ void heap_restrpos(HeapScanDesc scan) { /* XXX no amrestrpos checking that ammarkpos called */ if (!ItemPointerIsValid(&scan->rs_mctid)) { scan->rs_ctup.t_data = NULL; /* * unpin scan buffers */ if (BufferIsValid(scan->rs_cbuf)) ReleaseBuffer(scan->rs_cbuf); scan->rs_cbuf = InvalidBuffer; scan->rs_cblock = InvalidBlockNumber; scan->rs_inited = false; } else { /* * If we reached end of scan, rs_inited will now be false. We must * reset it to true to keep heapgettup from doing the wrong thing. */ scan->rs_inited = true; scan->rs_ctup.t_self = scan->rs_mctid; if (scan->rs_pageatatime) { scan->rs_cindex = scan->rs_mindex; heapgettup_pagemode(scan, NoMovementScanDirection, 0, /* needn't recheck scan keys */ NULL); } else heapgettup(scan, NoMovementScanDirection, 0, /* needn't recheck scan keys */ NULL); } } /* * If 'tuple' contains any visible XID greater than latestRemovedXid, * ratchet forwards latestRemovedXid to the greatest one found. * This is used as the basis for generating Hot Standby conflicts, so * if a tuple was never visible then removing it should not conflict * with queries. */ void HeapTupleHeaderAdvanceLatestRemovedXid(HeapTupleHeader tuple, TransactionId *latestRemovedXid) { TransactionId xmin = HeapTupleHeaderGetXmin(tuple); TransactionId xmax = HeapTupleHeaderGetUpdateXid(tuple); TransactionId xvac = HeapTupleHeaderGetXvac(tuple); if (tuple->t_infomask & HEAP_MOVED) { if (TransactionIdPrecedes(*latestRemovedXid, xvac)) *latestRemovedXid = xvac; } /* * Ignore tuples inserted by an aborted transaction or if the tuple was * updated/deleted by the inserting transaction. * * Look for a committed hint bit, or if no xmin bit is set, check clog. * This needs to work on both master and standby, where it is used to * assess btree delete records. */ if ((tuple->t_infomask & HEAP_XMIN_COMMITTED) || (!(tuple->t_infomask & HEAP_XMIN_COMMITTED) && !(tuple->t_infomask & HEAP_XMIN_INVALID) && TransactionIdDidCommit(xmin))) { if (xmax != xmin && TransactionIdFollows(xmax, *latestRemovedXid)) *latestRemovedXid = xmax; } /* *latestRemovedXid may still be invalid at end */ } /* * Perform XLogInsert to register a heap cleanup info message. These * messages are sent once per VACUUM and are required because * of the phasing of removal operations during a lazy VACUUM. * see comments for vacuum_log_cleanup_info(). */ XLogRecPtr log_heap_cleanup_info(RelFileNode rnode, TransactionId latestRemovedXid) { xl_heap_cleanup_info xlrec; XLogRecPtr recptr; XLogRecData rdata; xlrec.node = rnode; xlrec.latestRemovedXid = latestRemovedXid; rdata.data = (char *) &xlrec; rdata.len = SizeOfHeapCleanupInfo; rdata.buffer = InvalidBuffer; rdata.next = NULL; recptr = XLogInsert(RM_HEAP2_ID, XLOG_HEAP2_CLEANUP_INFO, &rdata); return recptr; } /* * Perform XLogInsert for a heap-clean operation. Caller must already * have modified the buffer and marked it dirty. * * Note: prior to Postgres 8.3, the entries in the nowunused[] array were * zero-based tuple indexes. Now they are one-based like other uses * of OffsetNumber. * * We also include latestRemovedXid, which is the greatest XID present in * the removed tuples. That allows recovery processing to cancel or wait * for long standby queries that can still see these tuples. */ XLogRecPtr log_heap_clean(Relation reln, Buffer buffer, OffsetNumber *redirected, int nredirected, OffsetNumber *nowdead, int ndead, OffsetNumber *nowunused, int nunused, TransactionId latestRemovedXid) { xl_heap_clean xlrec; uint8 info; XLogRecPtr recptr; XLogRecData rdata[4]; /* Caller should not call me on a non-WAL-logged relation */ Assert(RelationNeedsWAL(reln)); xlrec.node = reln->rd_node; xlrec.block = BufferGetBlockNumber(buffer); xlrec.latestRemovedXid = latestRemovedXid; xlrec.nredirected = nredirected; xlrec.ndead = ndead; rdata[0].data = (char *) &xlrec; rdata[0].len = SizeOfHeapClean; rdata[0].buffer = InvalidBuffer; rdata[0].next = &(rdata[1]); /* * The OffsetNumber arrays are not actually in the buffer, but we pretend * that they are. When XLogInsert stores the whole buffer, the offset * arrays need not be stored too. Note that even if all three arrays are * empty, we want to expose the buffer as a candidate for whole-page * storage, since this record type implies a defragmentation operation * even if no item pointers changed state. */ if (nredirected > 0) { rdata[1].data = (char *) redirected; rdata[1].len = nredirected * sizeof(OffsetNumber) * 2; } else { rdata[1].data = NULL; rdata[1].len = 0; } rdata[1].buffer = buffer; rdata[1].buffer_std = true; rdata[1].next = &(rdata[2]); if (ndead > 0) { rdata[2].data = (char *) nowdead; rdata[2].len = ndead * sizeof(OffsetNumber); } else { rdata[2].data = NULL; rdata[2].len = 0; } rdata[2].buffer = buffer; rdata[2].buffer_std = true; rdata[2].next = &(rdata[3]); if (nunused > 0) { rdata[3].data = (char *) nowunused; rdata[3].len = nunused * sizeof(OffsetNumber); } else { rdata[3].data = NULL; rdata[3].len = 0; } rdata[3].buffer = buffer; rdata[3].buffer_std = true; rdata[3].next = NULL; info = XLOG_HEAP2_CLEAN; recptr = XLogInsert(RM_HEAP2_ID, info, rdata); return recptr; } /* * Perform XLogInsert for a heap-freeze operation. Caller must already * have modified the buffer and marked it dirty. */ XLogRecPtr log_heap_freeze(Relation reln, Buffer buffer, TransactionId cutoff_xid, MultiXactId cutoff_multi, OffsetNumber *offsets, int offcnt) { xl_heap_freeze xlrec; XLogRecPtr recptr; XLogRecData rdata[2]; /* Caller should not call me on a non-WAL-logged relation */ Assert(RelationNeedsWAL(reln)); /* nor when there are no tuples to freeze */ Assert(offcnt > 0); xlrec.node = reln->rd_node; xlrec.block = BufferGetBlockNumber(buffer); xlrec.cutoff_xid = cutoff_xid; xlrec.cutoff_multi = cutoff_multi; rdata[0].data = (char *) &xlrec; rdata[0].len = SizeOfHeapFreeze; rdata[0].buffer = InvalidBuffer; rdata[0].next = &(rdata[1]); /* * The tuple-offsets array is not actually in the buffer, but pretend that * it is. When XLogInsert stores the whole buffer, the offsets array need * not be stored too. */ rdata[1].data = (char *) offsets; rdata[1].len = offcnt * sizeof(OffsetNumber); rdata[1].buffer = buffer; rdata[1].buffer_std = true; rdata[1].next = NULL; recptr = XLogInsert(RM_HEAP2_ID, XLOG_HEAP2_FREEZE, rdata); return recptr; } /* * Perform XLogInsert for a heap-visible operation. 'block' is the block * being marked all-visible, and vm_buffer is the buffer containing the * corresponding visibility map block. Both should have already been modified * and dirtied. * * If checksums are enabled, we also add the heap_buffer to the chain to * protect it from being torn. */ XLogRecPtr log_heap_visible(RelFileNode rnode, Buffer heap_buffer, Buffer vm_buffer, TransactionId cutoff_xid) { xl_heap_visible xlrec; XLogRecPtr recptr; XLogRecData rdata[3]; Assert(BufferIsValid(heap_buffer)); Assert(BufferIsValid(vm_buffer)); xlrec.node = rnode; xlrec.block = BufferGetBlockNumber(heap_buffer); xlrec.cutoff_xid = cutoff_xid; rdata[0].data = (char *) &xlrec; rdata[0].len = SizeOfHeapVisible; rdata[0].buffer = InvalidBuffer; rdata[0].next = &(rdata[1]); rdata[1].data = NULL; rdata[1].len = 0; rdata[1].buffer = vm_buffer; rdata[1].buffer_std = false; rdata[1].next = NULL; if (DataChecksumsEnabled()) { rdata[1].next = &(rdata[2]); rdata[2].data = NULL; rdata[2].len = 0; rdata[2].buffer = heap_buffer; rdata[2].buffer_std = true; rdata[2].next = NULL; } recptr = XLogInsert(RM_HEAP2_ID, XLOG_HEAP2_VISIBLE, rdata); return recptr; } /* * Perform XLogInsert for a heap-update operation. Caller must already * have modified the buffer(s) and marked them dirty. */ static XLogRecPtr log_heap_update(Relation reln, Buffer oldbuf, Buffer newbuf, HeapTuple oldtup, HeapTuple newtup, bool all_visible_cleared, bool new_all_visible_cleared) { xl_heap_update xlrec; xl_heap_header xlhdr; uint8 info; XLogRecPtr recptr; XLogRecData rdata[4]; Page page = BufferGetPage(newbuf); /* Caller should not call me on a non-WAL-logged relation */ Assert(RelationNeedsWAL(reln)); if (HeapTupleIsHeapOnly(newtup)) info = XLOG_HEAP_HOT_UPDATE; else info = XLOG_HEAP_UPDATE; xlrec.target.node = reln->rd_node; xlrec.target.tid = oldtup->t_self; xlrec.old_xmax = HeapTupleHeaderGetRawXmax(oldtup->t_data); xlrec.old_infobits_set = compute_infobits(oldtup->t_data->t_infomask, oldtup->t_data->t_infomask2); xlrec.new_xmax = HeapTupleHeaderGetRawXmax(newtup->t_data); xlrec.all_visible_cleared = all_visible_cleared; xlrec.newtid = newtup->t_self; xlrec.new_all_visible_cleared = new_all_visible_cleared; rdata[0].data = (char *) &xlrec; rdata[0].len = SizeOfHeapUpdate; rdata[0].buffer = InvalidBuffer; rdata[0].next = &(rdata[1]); rdata[1].data = NULL; rdata[1].len = 0; rdata[1].buffer = oldbuf; rdata[1].buffer_std = true; rdata[1].next = &(rdata[2]); xlhdr.t_infomask2 = newtup->t_data->t_infomask2; xlhdr.t_infomask = newtup->t_data->t_infomask; xlhdr.t_hoff = newtup->t_data->t_hoff; /* * As with insert records, we need not store the rdata[2] segment if we * decide to store the whole buffer instead. */ rdata[2].data = (char *) &xlhdr; rdata[2].len = SizeOfHeapHeader; rdata[2].buffer = newbuf; rdata[2].buffer_std = true; rdata[2].next = &(rdata[3]); /* PG73FORMAT: write bitmap [+ padding] [+ oid] + data */ rdata[3].data = (char *) newtup->t_data + offsetof(HeapTupleHeaderData, t_bits); rdata[3].len = newtup->t_len - offsetof(HeapTupleHeaderData, t_bits); rdata[3].buffer = newbuf; rdata[3].buffer_std = true; rdata[3].next = NULL; /* If new tuple is the single and first tuple on page... */ if (ItemPointerGetOffsetNumber(&(newtup->t_self)) == FirstOffsetNumber && PageGetMaxOffsetNumber(page) == FirstOffsetNumber) { info |= XLOG_HEAP_INIT_PAGE; rdata[2].buffer = rdata[3].buffer = InvalidBuffer; } recptr = XLogInsert(RM_HEAP_ID, info, rdata); return recptr; } /* * Perform XLogInsert of a HEAP_NEWPAGE record to WAL. Caller is responsible * for writing the page to disk after calling this routine. * * Note: If you're using this function, you should be building pages in private * memory and writing them directly to smgr. If you're using buffers, call * log_newpage_buffer instead. * * Note: the NEWPAGE log record is used for both heaps and indexes, so do * not do anything that assumes we are touching a heap. */ XLogRecPtr log_newpage(RelFileNode *rnode, ForkNumber forkNum, BlockNumber blkno, Page page) { xl_heap_newpage xlrec; XLogRecPtr recptr; XLogRecData rdata[2]; /* NO ELOG(ERROR) from here till newpage op is logged */ START_CRIT_SECTION(); xlrec.node = *rnode; xlrec.forknum = forkNum; xlrec.blkno = blkno; rdata[0].data = (char *) &xlrec; rdata[0].len = SizeOfHeapNewpage; rdata[0].buffer = InvalidBuffer; rdata[0].next = &(rdata[1]); rdata[1].data = (char *) page; rdata[1].len = BLCKSZ; rdata[1].buffer = InvalidBuffer; rdata[1].next = NULL; recptr = XLogInsert(RM_HEAP_ID, XLOG_HEAP_NEWPAGE, rdata); /* * The page may be uninitialized. If so, we can't set the LSN and TLI * because that would corrupt the page. */ if (!PageIsNew(page)) { PageSetLSN(page, recptr); } END_CRIT_SECTION(); return recptr; } /* * Perform XLogInsert of a HEAP_NEWPAGE record to WAL. * * Caller should initialize the buffer and mark it dirty before calling this * function. This function will set the page LSN and TLI. * * Note: the NEWPAGE log record is used for both heaps and indexes, so do * not do anything that assumes we are touching a heap. */ XLogRecPtr log_newpage_buffer(Buffer buffer) { xl_heap_newpage xlrec; XLogRecPtr recptr; XLogRecData rdata[2]; Page page = BufferGetPage(buffer); /* We should be in a critical section. */ Assert(CritSectionCount > 0); BufferGetTag(buffer, &xlrec.node, &xlrec.forknum, &xlrec.blkno); rdata[0].data = (char *) &xlrec; rdata[0].len = SizeOfHeapNewpage; rdata[0].buffer = InvalidBuffer; rdata[0].next = &(rdata[1]); rdata[1].data = page; rdata[1].len = BLCKSZ; rdata[1].buffer = InvalidBuffer; rdata[1].next = NULL; recptr = XLogInsert(RM_HEAP_ID, XLOG_HEAP_NEWPAGE, rdata); /* * The page may be uninitialized. If so, we can't set the LSN and TLI * because that would corrupt the page. */ if (!PageIsNew(page)) { PageSetLSN(page, recptr); } return recptr; } /* * Handles CLEANUP_INFO */ static void heap_xlog_cleanup_info(XLogRecPtr lsn, XLogRecord *record) { xl_heap_cleanup_info *xlrec = (xl_heap_cleanup_info *) XLogRecGetData(record); if (InHotStandby) ResolveRecoveryConflictWithSnapshot(xlrec->latestRemovedXid, xlrec->node); /* * Actual operation is a no-op. Record type exists to provide a means for * conflict processing to occur before we begin index vacuum actions. see * vacuumlazy.c and also comments in btvacuumpage() */ /* Backup blocks are not used in cleanup_info records */ Assert(!(record->xl_info & XLR_BKP_BLOCK_MASK)); } /* * Handles HEAP2_CLEAN record type */ static void heap_xlog_clean(XLogRecPtr lsn, XLogRecord *record) { xl_heap_clean *xlrec = (xl_heap_clean *) XLogRecGetData(record); Buffer buffer; Page page; OffsetNumber *end; OffsetNumber *redirected; OffsetNumber *nowdead; OffsetNumber *nowunused; int nredirected; int ndead; int nunused; Size freespace; /* * We're about to remove tuples. In Hot Standby mode, ensure that there's * no queries running for which the removed tuples are still visible. * * Not all HEAP2_CLEAN records remove tuples with xids, so we only want to * conflict on the records that cause MVCC failures for user queries. If * latestRemovedXid is invalid, skip conflict processing. */ if (InHotStandby && TransactionIdIsValid(xlrec->latestRemovedXid)) ResolveRecoveryConflictWithSnapshot(xlrec->latestRemovedXid, xlrec->node); /* * If we have a full-page image, restore it (using a cleanup lock) and * we're done. */ if (record->xl_info & XLR_BKP_BLOCK(0)) { (void) RestoreBackupBlock(lsn, record, 0, true, false); return; } buffer = XLogReadBufferExtended(xlrec->node, MAIN_FORKNUM, xlrec->block, RBM_NORMAL); if (!BufferIsValid(buffer)) return; LockBufferForCleanup(buffer); page = (Page) BufferGetPage(buffer); if (lsn <= PageGetLSN(page)) { UnlockReleaseBuffer(buffer); return; } nredirected = xlrec->nredirected; ndead = xlrec->ndead; end = (OffsetNumber *) ((char *) xlrec + record->xl_len); redirected = (OffsetNumber *) ((char *) xlrec + SizeOfHeapClean); nowdead = redirected + (nredirected * 2); nowunused = nowdead + ndead; nunused = (end - nowunused); Assert(nunused >= 0); /* Update all item pointers per the record, and repair fragmentation */ heap_page_prune_execute(buffer, redirected, nredirected, nowdead, ndead, nowunused, nunused); freespace = PageGetHeapFreeSpace(page); /* needed to update FSM below */ /* * Note: we don't worry about updating the page's prunability hints. At * worst this will cause an extra prune cycle to occur soon. */ PageSetLSN(page, lsn); MarkBufferDirty(buffer); UnlockReleaseBuffer(buffer); /* * Update the FSM as well. * * XXX: We don't get here if the page was restored from full page image. * We don't bother to update the FSM in that case, it doesn't need to be * totally accurate anyway. */ XLogRecordPageWithFreeSpace(xlrec->node, xlrec->block, freespace); } static void heap_xlog_freeze(XLogRecPtr lsn, XLogRecord *record) { xl_heap_freeze *xlrec = (xl_heap_freeze *) XLogRecGetData(record); TransactionId cutoff_xid = xlrec->cutoff_xid; MultiXactId cutoff_multi = xlrec->cutoff_multi; Buffer buffer; Page page; /* * In Hot Standby mode, ensure that there's no queries running which still * consider the frozen xids as running. */ if (InHotStandby) ResolveRecoveryConflictWithSnapshot(cutoff_xid, xlrec->node); /* If we have a full-page image, restore it and we're done */ if (record->xl_info & XLR_BKP_BLOCK(0)) { (void) RestoreBackupBlock(lsn, record, 0, false, false); return; } buffer = XLogReadBuffer(xlrec->node, xlrec->block, false); if (!BufferIsValid(buffer)) return; page = (Page) BufferGetPage(buffer); if (lsn <= PageGetLSN(page)) { UnlockReleaseBuffer(buffer); return; } if (record->xl_len > SizeOfHeapFreeze) { OffsetNumber *offsets; OffsetNumber *offsets_end; offsets = (OffsetNumber *) ((char *) xlrec + SizeOfHeapFreeze); offsets_end = (OffsetNumber *) ((char *) xlrec + record->xl_len); while (offsets < offsets_end) { /* offsets[] entries are one-based */ ItemId lp = PageGetItemId(page, *offsets); HeapTupleHeader tuple = (HeapTupleHeader) PageGetItem(page, lp); (void) heap_freeze_tuple(tuple, cutoff_xid, cutoff_multi); offsets++; } } PageSetLSN(page, lsn); MarkBufferDirty(buffer); UnlockReleaseBuffer(buffer); } /* * Replay XLOG_HEAP2_VISIBLE record. * * The critical integrity requirement here is that we must never end up with * a situation where the visibility map bit is set, and the page-level * PD_ALL_VISIBLE bit is clear. If that were to occur, then a subsequent * page modification would fail to clear the visibility map bit. */ static void heap_xlog_visible(XLogRecPtr lsn, XLogRecord *record) { xl_heap_visible *xlrec = (xl_heap_visible *) XLogRecGetData(record); /* * If there are any Hot Standby transactions running that have an xmin * horizon old enough that this page isn't all-visible for them, they * might incorrectly decide that an index-only scan can skip a heap fetch. * * NB: It might be better to throw some kind of "soft" conflict here that * forces any index-only scan that is in flight to perform heap fetches, * rather than killing the transaction outright. */ if (InHotStandby) ResolveRecoveryConflictWithSnapshot(xlrec->cutoff_xid, xlrec->node); /* * If heap block was backed up, restore it. This can only happen with * checksums enabled. */ if (record->xl_info & XLR_BKP_BLOCK(1)) { Assert(DataChecksumsEnabled()); (void) RestoreBackupBlock(lsn, record, 1, false, false); } else { Buffer buffer; Page page; /* * Read the heap page, if it still exists. If the heap file has been * dropped or truncated later in recovery, we don't need to update the * page, but we'd better still update the visibility map. */ buffer = XLogReadBufferExtended(xlrec->node, MAIN_FORKNUM, xlrec->block, RBM_NORMAL); if (BufferIsValid(buffer)) { LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE); page = (Page) BufferGetPage(buffer); /* * We don't bump the LSN of the heap page when setting the * visibility map bit (unless checksums are enabled, in which case * we must), because that would generate an unworkable volume of * full-page writes. This exposes us to torn page hazards, but * since we're not inspecting the existing page contents in any * way, we don't care. * * However, all operations that clear the visibility map bit *do* * bump the LSN, and those operations will only be replayed if the * XLOG LSN follows the page LSN. Thus, if the page LSN has * advanced past our XLOG record's LSN, we mustn't mark the page * all-visible, because the subsequent update won't be replayed to * clear the flag. */ if (lsn > PageGetLSN(page)) { PageSetAllVisible(page); MarkBufferDirty(buffer); } /* Done with heap page. */ UnlockReleaseBuffer(buffer); } } /* * Even if we skipped the heap page update due to the LSN interlock, it's * still safe to update the visibility map. Any WAL record that clears * the visibility map bit does so before checking the page LSN, so any * bits that need to be cleared will still be cleared. */ if (record->xl_info & XLR_BKP_BLOCK(0)) (void) RestoreBackupBlock(lsn, record, 0, false, false); else { Relation reln; Buffer vmbuffer = InvalidBuffer; reln = CreateFakeRelcacheEntry(xlrec->node); visibilitymap_pin(reln, xlrec->block, &vmbuffer); /* * Don't set the bit if replay has already passed this point. * * It might be safe to do this unconditionally; if replay has passed * this point, we'll replay at least as far this time as we did * before, and if this bit needs to be cleared, the record responsible * for doing so should be again replayed, and clear it. For right * now, out of an abundance of conservatism, we use the same test here * we did for the heap page. If this results in a dropped bit, no * real harm is done; and the next VACUUM will fix it. */ if (lsn > PageGetLSN(BufferGetPage(vmbuffer))) visibilitymap_set(reln, xlrec->block, InvalidBuffer, lsn, vmbuffer, xlrec->cutoff_xid); ReleaseBuffer(vmbuffer); FreeFakeRelcacheEntry(reln); } } static void heap_xlog_newpage(XLogRecPtr lsn, XLogRecord *record) { xl_heap_newpage *xlrec = (xl_heap_newpage *) XLogRecGetData(record); Buffer buffer; Page page; /* Backup blocks are not used in newpage records */ Assert(!(record->xl_info & XLR_BKP_BLOCK_MASK)); /* * Note: the NEWPAGE log record is used for both heaps and indexes, so do * not do anything that assumes we are touching a heap. */ buffer = XLogReadBufferExtended(xlrec->node, xlrec->forknum, xlrec->blkno, RBM_ZERO); Assert(BufferIsValid(buffer)); LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE); page = (Page) BufferGetPage(buffer); Assert(record->xl_len == SizeOfHeapNewpage + BLCKSZ); memcpy(page, (char *) xlrec + SizeOfHeapNewpage, BLCKSZ); /* * The page may be uninitialized. If so, we can't set the LSN because that * would corrupt the page. */ if (!PageIsNew(page)) { PageSetLSN(page, lsn); } MarkBufferDirty(buffer); UnlockReleaseBuffer(buffer); } /* * Given an "infobits" field from an XLog record, set the correct bits in the * given infomask and infomask2 for the tuple touched by the record. * * (This is the reverse of compute_infobits). */ static void fix_infomask_from_infobits(uint8 infobits, uint16 *infomask, uint16 *infomask2) { *infomask &= ~(HEAP_XMAX_IS_MULTI | HEAP_XMAX_LOCK_ONLY | HEAP_XMAX_KEYSHR_LOCK | HEAP_XMAX_EXCL_LOCK); *infomask2 &= ~HEAP_KEYS_UPDATED; if (infobits & XLHL_XMAX_IS_MULTI) *infomask |= HEAP_XMAX_IS_MULTI; if (infobits & XLHL_XMAX_LOCK_ONLY) *infomask |= HEAP_XMAX_LOCK_ONLY; if (infobits & XLHL_XMAX_EXCL_LOCK) *infomask |= HEAP_XMAX_EXCL_LOCK; /* note HEAP_XMAX_SHR_LOCK isn't considered here */ if (infobits & XLHL_XMAX_KEYSHR_LOCK) *infomask |= HEAP_XMAX_KEYSHR_LOCK; if (infobits & XLHL_KEYS_UPDATED) *infomask2 |= HEAP_KEYS_UPDATED; } static void heap_xlog_delete(XLogRecPtr lsn, XLogRecord *record) { xl_heap_delete *xlrec = (xl_heap_delete *) XLogRecGetData(record); Buffer buffer; Page page; OffsetNumber offnum; ItemId lp = NULL; HeapTupleHeader htup; BlockNumber blkno; blkno = ItemPointerGetBlockNumber(&(xlrec->target.tid)); /* * The visibility map may need to be fixed even if the heap page is * already up-to-date. */ if (xlrec->all_visible_cleared) { Relation reln = CreateFakeRelcacheEntry(xlrec->target.node); Buffer vmbuffer = InvalidBuffer; visibilitymap_pin(reln, blkno, &vmbuffer); visibilitymap_clear(reln, blkno, vmbuffer); ReleaseBuffer(vmbuffer); FreeFakeRelcacheEntry(reln); } /* If we have a full-page image, restore it and we're done */ if (record->xl_info & XLR_BKP_BLOCK(0)) { (void) RestoreBackupBlock(lsn, record, 0, false, false); return; } buffer = XLogReadBuffer(xlrec->target.node, blkno, false); if (!BufferIsValid(buffer)) return; page = (Page) BufferGetPage(buffer); if (lsn <= PageGetLSN(page)) /* changes are applied */ { UnlockReleaseBuffer(buffer); return; } offnum = ItemPointerGetOffsetNumber(&(xlrec->target.tid)); if (PageGetMaxOffsetNumber(page) >= offnum) lp = PageGetItemId(page, offnum); if (PageGetMaxOffsetNumber(page) < offnum || !ItemIdIsNormal(lp)) elog(PANIC, "heap_delete_redo: invalid lp"); htup = (HeapTupleHeader) PageGetItem(page, lp); htup->t_infomask &= ~(HEAP_XMAX_BITS | HEAP_MOVED); htup->t_infomask2 &= ~HEAP_KEYS_UPDATED; HeapTupleHeaderClearHotUpdated(htup); fix_infomask_from_infobits(xlrec->infobits_set, &htup->t_infomask, &htup->t_infomask2); HeapTupleHeaderSetXmax(htup, xlrec->xmax); HeapTupleHeaderSetCmax(htup, FirstCommandId, false); /* Mark the page as a candidate for pruning */ PageSetPrunable(page, record->xl_xid); if (xlrec->all_visible_cleared) PageClearAllVisible(page); /* Make sure there is no forward chain link in t_ctid */ htup->t_ctid = xlrec->target.tid; PageSetLSN(page, lsn); MarkBufferDirty(buffer); UnlockReleaseBuffer(buffer); } static void heap_xlog_insert(XLogRecPtr lsn, XLogRecord *record) { xl_heap_insert *xlrec = (xl_heap_insert *) XLogRecGetData(record); Buffer buffer; Page page; OffsetNumber offnum; struct { HeapTupleHeaderData hdr; char data[MaxHeapTupleSize]; } tbuf; HeapTupleHeader htup; xl_heap_header xlhdr; uint32 newlen; Size freespace; BlockNumber blkno; blkno = ItemPointerGetBlockNumber(&(xlrec->target.tid)); /* * The visibility map may need to be fixed even if the heap page is * already up-to-date. */ if (xlrec->all_visible_cleared) { Relation reln = CreateFakeRelcacheEntry(xlrec->target.node); Buffer vmbuffer = InvalidBuffer; visibilitymap_pin(reln, blkno, &vmbuffer); visibilitymap_clear(reln, blkno, vmbuffer); ReleaseBuffer(vmbuffer); FreeFakeRelcacheEntry(reln); } /* If we have a full-page image, restore it and we're done */ if (record->xl_info & XLR_BKP_BLOCK(0)) { (void) RestoreBackupBlock(lsn, record, 0, false, false); return; } if (record->xl_info & XLOG_HEAP_INIT_PAGE) { buffer = XLogReadBuffer(xlrec->target.node, blkno, true); Assert(BufferIsValid(buffer)); page = (Page) BufferGetPage(buffer); PageInit(page, BufferGetPageSize(buffer), 0); } else { buffer = XLogReadBuffer(xlrec->target.node, blkno, false); if (!BufferIsValid(buffer)) return; page = (Page) BufferGetPage(buffer); if (lsn <= PageGetLSN(page)) /* changes are applied */ { UnlockReleaseBuffer(buffer); return; } } offnum = ItemPointerGetOffsetNumber(&(xlrec->target.tid)); if (PageGetMaxOffsetNumber(page) + 1 < offnum) elog(PANIC, "heap_insert_redo: invalid max offset number"); newlen = record->xl_len - SizeOfHeapInsert - SizeOfHeapHeader; Assert(newlen <= MaxHeapTupleSize); memcpy((char *) &xlhdr, (char *) xlrec + SizeOfHeapInsert, SizeOfHeapHeader); htup = &tbuf.hdr; MemSet((char *) htup, 0, sizeof(HeapTupleHeaderData)); /* PG73FORMAT: get bitmap [+ padding] [+ oid] + data */ memcpy((char *) htup + offsetof(HeapTupleHeaderData, t_bits), (char *) xlrec + SizeOfHeapInsert + SizeOfHeapHeader, newlen); newlen += offsetof(HeapTupleHeaderData, t_bits); htup->t_infomask2 = xlhdr.t_infomask2; htup->t_infomask = xlhdr.t_infomask; htup->t_hoff = xlhdr.t_hoff; HeapTupleHeaderSetXmin(htup, record->xl_xid); HeapTupleHeaderSetCmin(htup, FirstCommandId); htup->t_ctid = xlrec->target.tid; offnum = PageAddItem(page, (Item) htup, newlen, offnum, true, true); if (offnum == InvalidOffsetNumber) elog(PANIC, "heap_insert_redo: failed to add tuple"); freespace = PageGetHeapFreeSpace(page); /* needed to update FSM below */ PageSetLSN(page, lsn); if (xlrec->all_visible_cleared) PageClearAllVisible(page); MarkBufferDirty(buffer); UnlockReleaseBuffer(buffer); /* * If the page is running low on free space, update the FSM as well. * Arbitrarily, our definition of "low" is less than 20%. We can't do much * better than that without knowing the fill-factor for the table. * * XXX: We don't get here if the page was restored from full page image. * We don't bother to update the FSM in that case, it doesn't need to be * totally accurate anyway. */ if (freespace < BLCKSZ / 5) XLogRecordPageWithFreeSpace(xlrec->target.node, blkno, freespace); } /* * Handles MULTI_INSERT record type. */ static void heap_xlog_multi_insert(XLogRecPtr lsn, XLogRecord *record) { char *recdata = XLogRecGetData(record); xl_heap_multi_insert *xlrec; Buffer buffer; Page page; struct { HeapTupleHeaderData hdr; char data[MaxHeapTupleSize]; } tbuf; HeapTupleHeader htup; uint32 newlen; Size freespace; BlockNumber blkno; int i; bool isinit = (record->xl_info & XLOG_HEAP_INIT_PAGE) != 0; /* * Insertion doesn't overwrite MVCC data, so no conflict processing is * required. */ xlrec = (xl_heap_multi_insert *) recdata; recdata += SizeOfHeapMultiInsert; /* * If we're reinitializing the page, the tuples are stored in order from * FirstOffsetNumber. Otherwise there's an array of offsets in the WAL * record. */ if (!isinit) recdata += sizeof(OffsetNumber) * xlrec->ntuples; blkno = xlrec->blkno; /* * The visibility map may need to be fixed even if the heap page is * already up-to-date. */ if (xlrec->all_visible_cleared) { Relation reln = CreateFakeRelcacheEntry(xlrec->node); Buffer vmbuffer = InvalidBuffer; visibilitymap_pin(reln, blkno, &vmbuffer); visibilitymap_clear(reln, blkno, vmbuffer); ReleaseBuffer(vmbuffer); FreeFakeRelcacheEntry(reln); } /* If we have a full-page image, restore it and we're done */ if (record->xl_info & XLR_BKP_BLOCK(0)) { (void) RestoreBackupBlock(lsn, record, 0, false, false); return; } if (isinit) { buffer = XLogReadBuffer(xlrec->node, blkno, true); Assert(BufferIsValid(buffer)); page = (Page) BufferGetPage(buffer); PageInit(page, BufferGetPageSize(buffer), 0); } else { buffer = XLogReadBuffer(xlrec->node, blkno, false); if (!BufferIsValid(buffer)) return; page = (Page) BufferGetPage(buffer); if (lsn <= PageGetLSN(page)) /* changes are applied */ { UnlockReleaseBuffer(buffer); return; } } for (i = 0; i < xlrec->ntuples; i++) { OffsetNumber offnum; xl_multi_insert_tuple *xlhdr; if (isinit) offnum = FirstOffsetNumber + i; else offnum = xlrec->offsets[i]; if (PageGetMaxOffsetNumber(page) + 1 < offnum) elog(PANIC, "heap_multi_insert_redo: invalid max offset number"); xlhdr = (xl_multi_insert_tuple *) SHORTALIGN(recdata); recdata = ((char *) xlhdr) + SizeOfMultiInsertTuple; newlen = xlhdr->datalen; Assert(newlen <= MaxHeapTupleSize); htup = &tbuf.hdr; MemSet((char *) htup, 0, sizeof(HeapTupleHeaderData)); /* PG73FORMAT: get bitmap [+ padding] [+ oid] + data */ memcpy((char *) htup + offsetof(HeapTupleHeaderData, t_bits), (char *) recdata, newlen); recdata += newlen; newlen += offsetof(HeapTupleHeaderData, t_bits); htup->t_infomask2 = xlhdr->t_infomask2; htup->t_infomask = xlhdr->t_infomask; htup->t_hoff = xlhdr->t_hoff; HeapTupleHeaderSetXmin(htup, record->xl_xid); HeapTupleHeaderSetCmin(htup, FirstCommandId); ItemPointerSetBlockNumber(&htup->t_ctid, blkno); ItemPointerSetOffsetNumber(&htup->t_ctid, offnum); offnum = PageAddItem(page, (Item) htup, newlen, offnum, true, true); if (offnum == InvalidOffsetNumber) elog(PANIC, "heap_multi_insert_redo: failed to add tuple"); } freespace = PageGetHeapFreeSpace(page); /* needed to update FSM below */ PageSetLSN(page, lsn); if (xlrec->all_visible_cleared) PageClearAllVisible(page); MarkBufferDirty(buffer); UnlockReleaseBuffer(buffer); /* * If the page is running low on free space, update the FSM as well. * Arbitrarily, our definition of "low" is less than 20%. We can't do much * better than that without knowing the fill-factor for the table. * * XXX: We don't get here if the page was restored from full page image. * We don't bother to update the FSM in that case, it doesn't need to be * totally accurate anyway. */ if (freespace < BLCKSZ / 5) XLogRecordPageWithFreeSpace(xlrec->node, blkno, freespace); } /* * Handles UPDATE and HOT_UPDATE */ static void heap_xlog_update(XLogRecPtr lsn, XLogRecord *record, bool hot_update) { xl_heap_update *xlrec = (xl_heap_update *) XLogRecGetData(record); bool samepage = (ItemPointerGetBlockNumber(&(xlrec->newtid)) == ItemPointerGetBlockNumber(&(xlrec->target.tid))); Buffer obuffer, nbuffer; Page page; OffsetNumber offnum; ItemId lp = NULL; HeapTupleHeader htup; struct { HeapTupleHeaderData hdr; char data[MaxHeapTupleSize]; } tbuf; xl_heap_header xlhdr; int hsize; uint32 newlen; Size freespace; /* * The visibility map may need to be fixed even if the heap page is * already up-to-date. */ if (xlrec->all_visible_cleared) { Relation reln = CreateFakeRelcacheEntry(xlrec->target.node); BlockNumber block = ItemPointerGetBlockNumber(&xlrec->target.tid); Buffer vmbuffer = InvalidBuffer; visibilitymap_pin(reln, block, &vmbuffer); visibilitymap_clear(reln, block, vmbuffer); ReleaseBuffer(vmbuffer); FreeFakeRelcacheEntry(reln); } /* * In normal operation, it is important to lock the two pages in * page-number order, to avoid possible deadlocks against other update * operations going the other way. However, during WAL replay there can * be no other update happening, so we don't need to worry about that. But * we *do* need to worry that we don't expose an inconsistent state to Hot * Standby queries --- so the original page can't be unlocked before we've * added the new tuple to the new page. */ if (record->xl_info & XLR_BKP_BLOCK(0)) { obuffer = RestoreBackupBlock(lsn, record, 0, false, true); if (samepage) { /* backup block covered both changes, so we're done */ UnlockReleaseBuffer(obuffer); return; } goto newt; } /* Deal with old tuple version */ obuffer = XLogReadBuffer(xlrec->target.node, ItemPointerGetBlockNumber(&(xlrec->target.tid)), false); if (!BufferIsValid(obuffer)) goto newt; page = (Page) BufferGetPage(obuffer); if (lsn <= PageGetLSN(page)) /* changes are applied */ { if (samepage) { UnlockReleaseBuffer(obuffer); return; } goto newt; } offnum = ItemPointerGetOffsetNumber(&(xlrec->target.tid)); if (PageGetMaxOffsetNumber(page) >= offnum) lp = PageGetItemId(page, offnum); if (PageGetMaxOffsetNumber(page) < offnum || !ItemIdIsNormal(lp)) elog(PANIC, "heap_update_redo: invalid lp"); htup = (HeapTupleHeader) PageGetItem(page, lp); htup->t_infomask &= ~(HEAP_XMAX_BITS | HEAP_MOVED); htup->t_infomask2 &= ~HEAP_KEYS_UPDATED; if (hot_update) HeapTupleHeaderSetHotUpdated(htup); else HeapTupleHeaderClearHotUpdated(htup); fix_infomask_from_infobits(xlrec->old_infobits_set, &htup->t_infomask, &htup->t_infomask2); HeapTupleHeaderSetXmax(htup, xlrec->old_xmax); HeapTupleHeaderSetCmax(htup, FirstCommandId, false); /* Set forward chain link in t_ctid */ htup->t_ctid = xlrec->newtid; /* Mark the page as a candidate for pruning */ PageSetPrunable(page, record->xl_xid); if (xlrec->all_visible_cleared) PageClearAllVisible(page); /* * this test is ugly, but necessary to avoid thinking that insert change * is already applied */ if (samepage) { nbuffer = obuffer; goto newsame; } PageSetLSN(page, lsn); MarkBufferDirty(obuffer); /* Deal with new tuple */ newt:; /* * The visibility map may need to be fixed even if the heap page is * already up-to-date. */ if (xlrec->new_all_visible_cleared) { Relation reln = CreateFakeRelcacheEntry(xlrec->target.node); BlockNumber block = ItemPointerGetBlockNumber(&xlrec->newtid); Buffer vmbuffer = InvalidBuffer; visibilitymap_pin(reln, block, &vmbuffer); visibilitymap_clear(reln, block, vmbuffer); ReleaseBuffer(vmbuffer); FreeFakeRelcacheEntry(reln); } if (record->xl_info & XLR_BKP_BLOCK(1)) { (void) RestoreBackupBlock(lsn, record, 1, false, false); if (BufferIsValid(obuffer)) UnlockReleaseBuffer(obuffer); return; } if (record->xl_info & XLOG_HEAP_INIT_PAGE) { nbuffer = XLogReadBuffer(xlrec->target.node, ItemPointerGetBlockNumber(&(xlrec->newtid)), true); Assert(BufferIsValid(nbuffer)); page = (Page) BufferGetPage(nbuffer); PageInit(page, BufferGetPageSize(nbuffer), 0); } else { nbuffer = XLogReadBuffer(xlrec->target.node, ItemPointerGetBlockNumber(&(xlrec->newtid)), false); if (!BufferIsValid(nbuffer)) { if (BufferIsValid(obuffer)) UnlockReleaseBuffer(obuffer); return; } page = (Page) BufferGetPage(nbuffer); if (lsn <= PageGetLSN(page)) /* changes are applied */ { UnlockReleaseBuffer(nbuffer); if (BufferIsValid(obuffer)) UnlockReleaseBuffer(obuffer); return; } } newsame:; offnum = ItemPointerGetOffsetNumber(&(xlrec->newtid)); if (PageGetMaxOffsetNumber(page) + 1 < offnum) elog(PANIC, "heap_update_redo: invalid max offset number"); hsize = SizeOfHeapUpdate + SizeOfHeapHeader; newlen = record->xl_len - hsize; Assert(newlen <= MaxHeapTupleSize); memcpy((char *) &xlhdr, (char *) xlrec + SizeOfHeapUpdate, SizeOfHeapHeader); htup = &tbuf.hdr; MemSet((char *) htup, 0, sizeof(HeapTupleHeaderData)); /* PG73FORMAT: get bitmap [+ padding] [+ oid] + data */ memcpy((char *) htup + offsetof(HeapTupleHeaderData, t_bits), (char *) xlrec + hsize, newlen); newlen += offsetof(HeapTupleHeaderData, t_bits); htup->t_infomask2 = xlhdr.t_infomask2; htup->t_infomask = xlhdr.t_infomask; htup->t_hoff = xlhdr.t_hoff; HeapTupleHeaderSetXmin(htup, record->xl_xid); HeapTupleHeaderSetCmin(htup, FirstCommandId); HeapTupleHeaderSetXmax(htup, xlrec->new_xmax); /* Make sure there is no forward chain link in t_ctid */ htup->t_ctid = xlrec->newtid; offnum = PageAddItem(page, (Item) htup, newlen, offnum, true, true); if (offnum == InvalidOffsetNumber) elog(PANIC, "heap_update_redo: failed to add tuple"); if (xlrec->new_all_visible_cleared) PageClearAllVisible(page); freespace = PageGetHeapFreeSpace(page); /* needed to update FSM below */ PageSetLSN(page, lsn); MarkBufferDirty(nbuffer); UnlockReleaseBuffer(nbuffer); if (BufferIsValid(obuffer) && obuffer != nbuffer) UnlockReleaseBuffer(obuffer); /* * If the new page is running low on free space, update the FSM as well. * Arbitrarily, our definition of "low" is less than 20%. We can't do much * better than that without knowing the fill-factor for the table. * * However, don't update the FSM on HOT updates, because after crash * recovery, either the old or the new tuple will certainly be dead and * prunable. After pruning, the page will have roughly as much free space * as it did before the update, assuming the new tuple is about the same * size as the old one. * * XXX: We don't get here if the page was restored from full page image. * We don't bother to update the FSM in that case, it doesn't need to be * totally accurate anyway. */ if (!hot_update && freespace < BLCKSZ / 5) XLogRecordPageWithFreeSpace(xlrec->target.node, ItemPointerGetBlockNumber(&(xlrec->newtid)), freespace); } static void heap_xlog_lock(XLogRecPtr lsn, XLogRecord *record) { xl_heap_lock *xlrec = (xl_heap_lock *) XLogRecGetData(record); Buffer buffer; Page page; OffsetNumber offnum; ItemId lp = NULL; HeapTupleHeader htup; /* If we have a full-page image, restore it and we're done */ if (record->xl_info & XLR_BKP_BLOCK(0)) { (void) RestoreBackupBlock(lsn, record, 0, false, false); return; } buffer = XLogReadBuffer(xlrec->target.node, ItemPointerGetBlockNumber(&(xlrec->target.tid)), false); if (!BufferIsValid(buffer)) return; page = (Page) BufferGetPage(buffer); if (lsn <= PageGetLSN(page)) /* changes are applied */ { UnlockReleaseBuffer(buffer); return; } offnum = ItemPointerGetOffsetNumber(&(xlrec->target.tid)); if (PageGetMaxOffsetNumber(page) >= offnum) lp = PageGetItemId(page, offnum); if (PageGetMaxOffsetNumber(page) < offnum || !ItemIdIsNormal(lp)) elog(PANIC, "heap_lock_redo: invalid lp"); htup = (HeapTupleHeader) PageGetItem(page, lp); fix_infomask_from_infobits(xlrec->infobits_set, &htup->t_infomask, &htup->t_infomask2); HeapTupleHeaderClearHotUpdated(htup); HeapTupleHeaderSetXmax(htup, xlrec->locking_xid); HeapTupleHeaderSetCmax(htup, FirstCommandId, false); /* Make sure there is no forward chain link in t_ctid */ htup->t_ctid = xlrec->target.tid; PageSetLSN(page, lsn); MarkBufferDirty(buffer); UnlockReleaseBuffer(buffer); } static void heap_xlog_lock_updated(XLogRecPtr lsn, XLogRecord *record) { xl_heap_lock_updated *xlrec = (xl_heap_lock_updated *) XLogRecGetData(record); Buffer buffer; Page page; OffsetNumber offnum; ItemId lp = NULL; HeapTupleHeader htup; /* If we have a full-page image, restore it and we're done */ if (record->xl_info & XLR_BKP_BLOCK(0)) { (void) RestoreBackupBlock(lsn, record, 0, false, false); return; } buffer = XLogReadBuffer(xlrec->target.node, ItemPointerGetBlockNumber(&(xlrec->target.tid)), false); if (!BufferIsValid(buffer)) return; page = (Page) BufferGetPage(buffer); if (lsn <= PageGetLSN(page)) /* changes are applied */ { UnlockReleaseBuffer(buffer); return; } offnum = ItemPointerGetOffsetNumber(&(xlrec->target.tid)); if (PageGetMaxOffsetNumber(page) >= offnum) lp = PageGetItemId(page, offnum); if (PageGetMaxOffsetNumber(page) < offnum || !ItemIdIsNormal(lp)) elog(PANIC, "heap_xlog_lock_updated: invalid lp"); htup = (HeapTupleHeader) PageGetItem(page, lp); fix_infomask_from_infobits(xlrec->infobits_set, &htup->t_infomask, &htup->t_infomask2); HeapTupleHeaderSetXmax(htup, xlrec->xmax); PageSetLSN(page, lsn); MarkBufferDirty(buffer); UnlockReleaseBuffer(buffer); } static void heap_xlog_inplace(XLogRecPtr lsn, XLogRecord *record) { xl_heap_inplace *xlrec = (xl_heap_inplace *) XLogRecGetData(record); Buffer buffer; Page page; OffsetNumber offnum; ItemId lp = NULL; HeapTupleHeader htup; uint32 oldlen; uint32 newlen; /* If we have a full-page image, restore it and we're done */ if (record->xl_info & XLR_BKP_BLOCK(0)) { (void) RestoreBackupBlock(lsn, record, 0, false, false); return; } buffer = XLogReadBuffer(xlrec->target.node, ItemPointerGetBlockNumber(&(xlrec->target.tid)), false); if (!BufferIsValid(buffer)) return; page = (Page) BufferGetPage(buffer); if (lsn <= PageGetLSN(page)) /* changes are applied */ { UnlockReleaseBuffer(buffer); return; } offnum = ItemPointerGetOffsetNumber(&(xlrec->target.tid)); if (PageGetMaxOffsetNumber(page) >= offnum) lp = PageGetItemId(page, offnum); if (PageGetMaxOffsetNumber(page) < offnum || !ItemIdIsNormal(lp)) elog(PANIC, "heap_inplace_redo: invalid lp"); htup = (HeapTupleHeader) PageGetItem(page, lp); oldlen = ItemIdGetLength(lp) - htup->t_hoff; newlen = record->xl_len - SizeOfHeapInplace; if (oldlen != newlen) elog(PANIC, "heap_inplace_redo: wrong tuple length"); memcpy((char *) htup + htup->t_hoff, (char *) xlrec + SizeOfHeapInplace, newlen); PageSetLSN(page, lsn); MarkBufferDirty(buffer); UnlockReleaseBuffer(buffer); } void heap_redo(XLogRecPtr lsn, XLogRecord *record) { uint8 info = record->xl_info & ~XLR_INFO_MASK; /* * These operations don't overwrite MVCC data so no conflict processing is * required. The ones in heap2 rmgr do. */ switch (info & XLOG_HEAP_OPMASK) { case XLOG_HEAP_INSERT: heap_xlog_insert(lsn, record); break; case XLOG_HEAP_DELETE: heap_xlog_delete(lsn, record); break; case XLOG_HEAP_UPDATE: heap_xlog_update(lsn, record, false); break; case XLOG_HEAP_HOT_UPDATE: heap_xlog_update(lsn, record, true); break; case XLOG_HEAP_NEWPAGE: heap_xlog_newpage(lsn, record); break; case XLOG_HEAP_LOCK: heap_xlog_lock(lsn, record); break; case XLOG_HEAP_INPLACE: heap_xlog_inplace(lsn, record); break; default: elog(PANIC, "heap_redo: unknown op code %u", info); } } void heap2_redo(XLogRecPtr lsn, XLogRecord *record) { uint8 info = record->xl_info & ~XLR_INFO_MASK; switch (info & XLOG_HEAP_OPMASK) { case XLOG_HEAP2_FREEZE: heap_xlog_freeze(lsn, record); break; case XLOG_HEAP2_CLEAN: heap_xlog_clean(lsn, record); break; case XLOG_HEAP2_CLEANUP_INFO: heap_xlog_cleanup_info(lsn, record); break; case XLOG_HEAP2_VISIBLE: heap_xlog_visible(lsn, record); break; case XLOG_HEAP2_MULTI_INSERT: heap_xlog_multi_insert(lsn, record); break; case XLOG_HEAP2_LOCK_UPDATED: heap_xlog_lock_updated(lsn, record); break; default: elog(PANIC, "heap2_redo: unknown op code %u", info); } } /* * heap_sync - sync a heap, for use when no WAL has been written * * This forces the heap contents (including TOAST heap if any) down to disk. * If we skipped using WAL, and WAL is otherwise needed, we must force the * relation down to disk before it's safe to commit the transaction. This * requires writing out any dirty buffers and then doing a forced fsync. * * Indexes are not touched. (Currently, index operations associated with * the commands that use this are WAL-logged and so do not need fsync. * That behavior might change someday, but in any case it's likely that * any fsync decisions required would be per-index and hence not appropriate * to be done here.) */ void heap_sync(Relation rel) { /* non-WAL-logged tables never need fsync */ if (!RelationNeedsWAL(rel)) return; /* main heap */ FlushRelationBuffers(rel); /* FlushRelationBuffers will have opened rd_smgr */ smgrimmedsync(rel->rd_smgr, MAIN_FORKNUM); /* FSM is not critical, don't bother syncing it */ /* toast heap, if any */ if (OidIsValid(rel->rd_rel->reltoastrelid)) { Relation toastrel; toastrel = heap_open(rel->rd_rel->reltoastrelid, AccessShareLock); FlushRelationBuffers(toastrel); smgrimmedsync(toastrel->rd_smgr, MAIN_FORKNUM); heap_close(toastrel, AccessShareLock); } }