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postgresql/src/backend/access/nbtree/nbtinsert.c

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/*-------------------------------------------------------------------------
*
* nbtinsert.c
* Item insertion in Lehman and Yao btrees for Postgres.
*
* Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/access/nbtree/nbtinsert.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/nbtree.h"
#include "access/nbtxlog.h"
#include "access/transam.h"
#include "access/xloginsert.h"
#include "common/int.h"
#include "common/pg_prng.h"
#include "lib/qunique.h"
#include "miscadmin.h"
#include "storage/lmgr.h"
#include "storage/predicate.h"
#include "storage/smgr.h"
/* Minimum tree height for application of fastpath optimization */
#define BTREE_FASTPATH_MIN_LEVEL 2
static BTStack _bt_search_insert(Relation rel, Relation heaprel,
BTInsertState insertstate);
static TransactionId _bt_check_unique(Relation rel, BTInsertState insertstate,
Relation heapRel,
IndexUniqueCheck checkUnique, bool *is_unique,
uint32 *speculativeToken);
static OffsetNumber _bt_findinsertloc(Relation rel,
BTInsertState insertstate,
bool checkingunique,
bool indexUnchanged,
BTStack stack,
Relation heapRel);
static void _bt_stepright(Relation rel, Relation heaprel,
BTInsertState insertstate, BTStack stack);
static void _bt_insertonpg(Relation rel, Relation heaprel, BTScanInsert itup_key,
Buffer buf,
Buffer cbuf,
BTStack stack,
IndexTuple itup,
Size itemsz,
OffsetNumber newitemoff,
int postingoff,
bool split_only_page);
static Buffer _bt_split(Relation rel, Relation heaprel, BTScanInsert itup_key,
Buffer buf, Buffer cbuf, OffsetNumber newitemoff,
Size newitemsz, IndexTuple newitem, IndexTuple orignewitem,
IndexTuple nposting, uint16 postingoff);
static void _bt_insert_parent(Relation rel, Relation heaprel, Buffer buf,
Buffer rbuf, BTStack stack, bool isroot, bool isonly);
static Buffer _bt_newlevel(Relation rel, Relation heaprel, Buffer lbuf, Buffer rbuf);
static inline bool _bt_pgaddtup(Page page, Size itemsize, IndexTuple itup,
OffsetNumber itup_off, bool newfirstdataitem);
static void _bt_delete_or_dedup_one_page(Relation rel, Relation heapRel,
BTInsertState insertstate,
bool simpleonly, bool checkingunique,
bool uniquedup, bool indexUnchanged);
static void _bt_simpledel_pass(Relation rel, Buffer buffer, Relation heapRel,
OffsetNumber *deletable, int ndeletable,
IndexTuple newitem, OffsetNumber minoff,
OffsetNumber maxoff);
static BlockNumber *_bt_deadblocks(Page page, OffsetNumber *deletable,
int ndeletable, IndexTuple newitem,
int *nblocks);
static inline int _bt_blk_cmp(const void *arg1, const void *arg2);
/*
* _bt_doinsert() -- Handle insertion of a single index tuple in the tree.
*
* This routine is called by the public interface routine, btinsert.
* By here, itup is filled in, including the TID.
*
* If checkUnique is UNIQUE_CHECK_NO or UNIQUE_CHECK_PARTIAL, this
* will allow duplicates. Otherwise (UNIQUE_CHECK_YES or
* UNIQUE_CHECK_EXISTING) it will throw error for a duplicate.
* For UNIQUE_CHECK_EXISTING we merely run the duplicate check, and
* don't actually insert.
*
* indexUnchanged executor hint indicates if itup is from an
* UPDATE that didn't logically change the indexed value, but
* must nevertheless have a new entry to point to a successor
* version.
*
* The result value is only significant for UNIQUE_CHECK_PARTIAL:
* it must be true if the entry is known unique, else false.
* (In the current implementation we'll also return true after a
* successful UNIQUE_CHECK_YES or UNIQUE_CHECK_EXISTING call, but
* that's just a coding artifact.)
*/
bool
_bt_doinsert(Relation rel, IndexTuple itup,
IndexUniqueCheck checkUnique, bool indexUnchanged,
Relation heapRel)
{
bool is_unique = false;
BTInsertStateData insertstate;
BTScanInsert itup_key;
BTStack stack;
bool checkingunique = (checkUnique != UNIQUE_CHECK_NO);
/* we need an insertion scan key to do our search, so build one */
itup_key = _bt_mkscankey(rel, itup);
if (checkingunique)
{
if (!itup_key->anynullkeys)
{
/* No (heapkeyspace) scantid until uniqueness established */
itup_key->scantid = NULL;
}
else
{
/*
* Scan key for new tuple contains NULL key values. Bypass
* checkingunique steps. They are unnecessary because core code
* considers NULL unequal to every value, including NULL.
*
* This optimization avoids O(N^2) behavior within the
* _bt_findinsertloc() heapkeyspace path when a unique index has a
* large number of "duplicates" with NULL key values.
*/
checkingunique = false;
/* Tuple is unique in the sense that core code cares about */
Assert(checkUnique != UNIQUE_CHECK_EXISTING);
is_unique = true;
}
}
/*
* Fill in the BTInsertState working area, to track the current page and
* position within the page to insert on.
*
* Note that itemsz is passed down to lower level code that deals with
* inserting the item. It must be MAXALIGN()'d. This ensures that space
* accounting code consistently considers the alignment overhead that we
* expect PageAddItem() will add later. (Actually, index_form_tuple() is
* already conservative about alignment, but we don't rely on that from
* this distance. Besides, preserving the "true" tuple size in index
* tuple headers for the benefit of nbtsplitloc.c might happen someday.
* Note that heapam does not MAXALIGN() each heap tuple's lp_len field.)
*/
insertstate.itup = itup;
insertstate.itemsz = MAXALIGN(IndexTupleSize(itup));
insertstate.itup_key = itup_key;
insertstate.bounds_valid = false;
insertstate.buf = InvalidBuffer;
insertstate.postingoff = 0;
search:
/*
* Find and lock the leaf page that the tuple should be added to by
* searching from the root page. insertstate.buf will hold a buffer that
* is locked in exclusive mode afterwards.
*/
stack = _bt_search_insert(rel, heapRel, &insertstate);
/*
* checkingunique inserts are not allowed to go ahead when two tuples with
* equal key attribute values would be visible to new MVCC snapshots once
* the xact commits. Check for conflicts in the locked page/buffer (if
* needed) here.
*
* It might be necessary to check a page to the right in _bt_check_unique,
* though that should be very rare. In practice the first page the value
* could be on (with scantid omitted) is almost always also the only page
* that a matching tuple might be found on. This is due to the behavior
* of _bt_findsplitloc with duplicate tuples -- a group of duplicates can
* only be allowed to cross a page boundary when there is no candidate
* leaf page split point that avoids it. Also, _bt_check_unique can use
* the leaf page high key to determine that there will be no duplicates on
* the right sibling without actually visiting it (it uses the high key in
* cases where the new item happens to belong at the far right of the leaf
* page).
*
* NOTE: obviously, _bt_check_unique can only detect keys that are already
* in the index; so it cannot defend against concurrent insertions of the
* same key. We protect against that by means of holding a write lock on
* the first page the value could be on, with omitted/-inf value for the
* implicit heap TID tiebreaker attribute. Any other would-be inserter of
* the same key must acquire a write lock on the same page, so only one
* would-be inserter can be making the check at one time. Furthermore,
* once we are past the check we hold write locks continuously until we
* have performed our insertion, so no later inserter can fail to see our
* insertion. (This requires some care in _bt_findinsertloc.)
*
* If we must wait for another xact, we release the lock while waiting,
* and then must perform a new search.
*
* For a partial uniqueness check, we don't wait for the other xact. Just
* let the tuple in and return false for possibly non-unique, or true for
* definitely unique.
*/
if (checkingunique)
{
TransactionId xwait;
uint32 speculativeToken;
xwait = _bt_check_unique(rel, &insertstate, heapRel, checkUnique,
&is_unique, &speculativeToken);
if (unlikely(TransactionIdIsValid(xwait)))
{
/* Have to wait for the other guy ... */
_bt_relbuf(rel, insertstate.buf);
insertstate.buf = InvalidBuffer;
/*
* If it's a speculative insertion, wait for it to finish (ie. to
* go ahead with the insertion, or kill the tuple). Otherwise
* wait for the transaction to finish as usual.
*/
if (speculativeToken)
SpeculativeInsertionWait(xwait, speculativeToken);
else
XactLockTableWait(xwait, rel, &itup->t_tid, XLTW_InsertIndex);
/* start over... */
if (stack)
_bt_freestack(stack);
goto search;
}
/* Uniqueness is established -- restore heap tid as scantid */
if (itup_key->heapkeyspace)
itup_key->scantid = &itup->t_tid;
}
if (checkUnique != UNIQUE_CHECK_EXISTING)
{
OffsetNumber newitemoff;
/*
* The only conflict predicate locking cares about for indexes is when
* an index tuple insert conflicts with an existing lock. We don't
* know the actual page we're going to insert on for sure just yet in
* checkingunique and !heapkeyspace cases, but it's okay to use the
* first page the value could be on (with scantid omitted) instead.
*/
CheckForSerializableConflictIn(rel, NULL, BufferGetBlockNumber(insertstate.buf));
/*
* Do the insertion. Note that insertstate contains cached binary
* search bounds established within _bt_check_unique when insertion is
* checkingunique.
*/
newitemoff = _bt_findinsertloc(rel, &insertstate, checkingunique,
indexUnchanged, stack, heapRel);
_bt_insertonpg(rel, heapRel, itup_key, insertstate.buf, InvalidBuffer,
stack, itup, insertstate.itemsz, newitemoff,
insertstate.postingoff, false);
}
else
{
/* just release the buffer */
_bt_relbuf(rel, insertstate.buf);
}
/* be tidy */
if (stack)
_bt_freestack(stack);
pfree(itup_key);
return is_unique;
}
/*
* _bt_search_insert() -- _bt_search() wrapper for inserts
*
* Search the tree for a particular scankey, or more precisely for the first
* leaf page it could be on. Try to make use of the fastpath optimization's
* rightmost leaf page cache before actually searching the tree from the root
* page, though.
*
* Return value is a stack of parent-page pointers (though see notes about
* fastpath optimization and page splits below). insertstate->buf is set to
* the address of the leaf-page buffer, which is write-locked and pinned in
* all cases (if necessary by creating a new empty root page for caller).
*
* The fastpath optimization avoids most of the work of searching the tree
* repeatedly when a single backend inserts successive new tuples on the
* rightmost leaf page of an index. A backend cache of the rightmost leaf
* page is maintained within _bt_insertonpg(), and used here. The cache is
* invalidated here when an insert of a non-pivot tuple must take place on a
* non-rightmost leaf page.
*
* The optimization helps with indexes on an auto-incremented field. It also
* helps with indexes on datetime columns, as well as indexes with lots of
* NULL values. (NULLs usually get inserted in the rightmost page for single
* column indexes, since they usually get treated as coming after everything
* else in the key space. Individual NULL tuples will generally be placed on
* the rightmost leaf page due to the influence of the heap TID column.)
*
* Note that we avoid applying the optimization when there is insufficient
* space on the rightmost page to fit caller's new item. This is necessary
* because we'll need to return a real descent stack when a page split is
* expected (actually, caller can cope with a leaf page split that uses a NULL
* stack, but that's very slow and so must be avoided). Note also that the
* fastpath optimization acquires the lock on the page conditionally as a way
* of reducing extra contention when there are concurrent insertions into the
* rightmost page (we give up if we'd have to wait for the lock). We assume
* that it isn't useful to apply the optimization when there is contention,
* since each per-backend cache won't stay valid for long.
*/
static BTStack
_bt_search_insert(Relation rel, Relation heaprel, BTInsertState insertstate)
{
Assert(insertstate->buf == InvalidBuffer);
Assert(!insertstate->bounds_valid);
Assert(insertstate->postingoff == 0);
if (RelationGetTargetBlock(rel) != InvalidBlockNumber)
{
/* Simulate a _bt_getbuf() call with conditional locking */
insertstate->buf = ReadBuffer(rel, RelationGetTargetBlock(rel));
if (_bt_conditionallockbuf(rel, insertstate->buf))
{
Page page;
BTPageOpaque opaque;
_bt_checkpage(rel, insertstate->buf);
page = BufferGetPage(insertstate->buf);
opaque = BTPageGetOpaque(page);
/*
* Check if the page is still the rightmost leaf page and has
* enough free space to accommodate the new tuple. Also check
* that the insertion scan key is strictly greater than the first
* non-pivot tuple on the page. (Note that we expect itup_key's
* scantid to be unset when our caller is a checkingunique
* inserter.)
*/
if (P_RIGHTMOST(opaque) &&
P_ISLEAF(opaque) &&
!P_IGNORE(opaque) &&
PageGetFreeSpace(page) > insertstate->itemsz &&
PageGetMaxOffsetNumber(page) >= P_HIKEY &&
_bt_compare(rel, insertstate->itup_key, page, P_HIKEY) > 0)
{
/*
* Caller can use the fastpath optimization because cached
* block is still rightmost leaf page, which can fit caller's
* new tuple without splitting. Keep block in local cache for
* next insert, and have caller use NULL stack.
*
* Note that _bt_insert_parent() has an assertion that catches
* leaf page splits that somehow follow from a fastpath insert
* (it should only be passed a NULL stack when it must deal
* with a concurrent root page split, and never because a NULL
* stack was returned here).
*/
return NULL;
}
/* Page unsuitable for caller, drop lock and pin */
_bt_relbuf(rel, insertstate->buf);
}
else
{
/* Lock unavailable, drop pin */
ReleaseBuffer(insertstate->buf);
}
/* Forget block, since cache doesn't appear to be useful */
RelationSetTargetBlock(rel, InvalidBlockNumber);
}
/* Cannot use optimization -- descend tree, return proper descent stack */
return _bt_search(rel, heaprel, insertstate->itup_key, &insertstate->buf,
BT_WRITE);
}
/*
* _bt_check_unique() -- Check for violation of unique index constraint
*
* Returns InvalidTransactionId if there is no conflict, else an xact ID
* we must wait for to see if it commits a conflicting tuple. If an actual
* conflict is detected, no return --- just ereport(). If an xact ID is
* returned, and the conflicting tuple still has a speculative insertion in
* progress, *speculativeToken is set to non-zero, and the caller can wait for
* the verdict on the insertion using SpeculativeInsertionWait().
*
* However, if checkUnique == UNIQUE_CHECK_PARTIAL, we always return
* InvalidTransactionId because we don't want to wait. In this case we
* set *is_unique to false if there is a potential conflict, and the
* core code must redo the uniqueness check later.
*
* As a side-effect, sets state in insertstate that can later be used by
* _bt_findinsertloc() to reuse most of the binary search work we do
* here.
*
* This code treats NULLs as equal, unlike the default semantics for unique
* indexes. So do not call here when there are NULL values in scan key and
* the index uses the default NULLS DISTINCT mode.
*/
static TransactionId
_bt_check_unique(Relation rel, BTInsertState insertstate, Relation heapRel,
IndexUniqueCheck checkUnique, bool *is_unique,
uint32 *speculativeToken)
{
IndexTuple itup = insertstate->itup;
IndexTuple curitup = NULL;
ItemId curitemid = NULL;
BTScanInsert itup_key = insertstate->itup_key;
SnapshotData SnapshotDirty;
OffsetNumber offset;
OffsetNumber maxoff;
Page page;
BTPageOpaque opaque;
Buffer nbuf = InvalidBuffer;
bool found = false;
bool inposting = false;
bool prevalldead = true;
int curposti = 0;
/* Assume unique until we find a duplicate */
*is_unique = true;
InitDirtySnapshot(SnapshotDirty);
page = BufferGetPage(insertstate->buf);
opaque = BTPageGetOpaque(page);
maxoff = PageGetMaxOffsetNumber(page);
/*
* Find the first tuple with the same key.
*
* This also saves the binary search bounds in insertstate. We use them
* in the fastpath below, but also in the _bt_findinsertloc() call later.
*/
Assert(!insertstate->bounds_valid);
offset = _bt_binsrch_insert(rel, insertstate);
/*
* Scan over all equal tuples, looking for live conflicts.
*/
Assert(!insertstate->bounds_valid || insertstate->low == offset);
Assert(!itup_key->anynullkeys);
Assert(itup_key->scantid == NULL);
for (;;)
{
/*
* Each iteration of the loop processes one heap TID, not one index
* tuple. Current offset number for page isn't usually advanced on
* iterations that process heap TIDs from posting list tuples.
*
* "inposting" state is set when _inside_ a posting list --- not when
* we're at the start (or end) of a posting list. We advance curposti
* at the end of the iteration when inside a posting list tuple. In
* general, every loop iteration either advances the page offset or
* advances curposti --- an iteration that handles the rightmost/max
* heap TID in a posting list finally advances the page offset (and
* unsets "inposting").
*
* Make sure the offset points to an actual index tuple before trying
* to examine it...
*/
if (offset <= maxoff)
{
/*
* Fastpath: In most cases, we can use cached search bounds to
* limit our consideration to items that are definitely
* duplicates. This fastpath doesn't apply when the original page
* is empty, or when initial offset is past the end of the
* original page, which may indicate that we need to examine a
* second or subsequent page.
*
* Note that this optimization allows us to avoid calling
* _bt_compare() directly when there are no duplicates, as long as
* the offset where the key will go is not at the end of the page.
*/
if (nbuf == InvalidBuffer && offset == insertstate->stricthigh)
{
Assert(insertstate->bounds_valid);
Assert(insertstate->low >= P_FIRSTDATAKEY(opaque));
Assert(insertstate->low <= insertstate->stricthigh);
Assert(_bt_compare(rel, itup_key, page, offset) < 0);
break;
}
/*
* We can skip items that are already marked killed.
*
* In the presence of heavy update activity an index may contain
* many killed items with the same key; running _bt_compare() on
* each killed item gets expensive. Just advance over killed
* items as quickly as we can. We only apply _bt_compare() when
* we get to a non-killed item. We could reuse the bounds to
* avoid _bt_compare() calls for known equal tuples, but it
* doesn't seem worth it.
*/
if (!inposting)
curitemid = PageGetItemId(page, offset);
if (inposting || !ItemIdIsDead(curitemid))
{
ItemPointerData htid;
bool all_dead = false;
if (!inposting)
{
/* Plain tuple, or first TID in posting list tuple */
if (_bt_compare(rel, itup_key, page, offset) != 0)
break; /* we're past all the equal tuples */
/* Advanced curitup */
curitup = (IndexTuple) PageGetItem(page, curitemid);
Assert(!BTreeTupleIsPivot(curitup));
}
/* okay, we gotta fetch the heap tuple using htid ... */
if (!BTreeTupleIsPosting(curitup))
{
/* ... htid is from simple non-pivot tuple */
Assert(!inposting);
htid = curitup->t_tid;
}
else if (!inposting)
{
/* ... htid is first TID in new posting list */
inposting = true;
prevalldead = true;
curposti = 0;
htid = *BTreeTupleGetPostingN(curitup, 0);
}
else
{
/* ... htid is second or subsequent TID in posting list */
Assert(curposti > 0);
htid = *BTreeTupleGetPostingN(curitup, curposti);
}
/*
* If we are doing a recheck, we expect to find the tuple we
* are rechecking. It's not a duplicate, but we have to keep
* scanning.
*/
if (checkUnique == UNIQUE_CHECK_EXISTING &&
ItemPointerCompare(&htid, &itup->t_tid) == 0)
{
found = true;
}
/*
* Check if there's any table tuples for this index entry
* satisfying SnapshotDirty. This is necessary because for AMs
* with optimizations like heap's HOT, we have just a single
* index entry for the entire chain.
*/
else if (table_index_fetch_tuple_check(heapRel, &htid,
&SnapshotDirty,
&all_dead))
{
TransactionId xwait;
/*
* It is a duplicate. If we are only doing a partial
* check, then don't bother checking if the tuple is being
* updated in another transaction. Just return the fact
* that it is a potential conflict and leave the full
* check till later. Don't invalidate binary search
* bounds.
*/
if (checkUnique == UNIQUE_CHECK_PARTIAL)
{
if (nbuf != InvalidBuffer)
_bt_relbuf(rel, nbuf);
*is_unique = false;
return InvalidTransactionId;
}
/*
* If this tuple is being updated by other transaction
* then we have to wait for its commit/abort.
*/
xwait = (TransactionIdIsValid(SnapshotDirty.xmin)) ?
SnapshotDirty.xmin : SnapshotDirty.xmax;
if (TransactionIdIsValid(xwait))
{
if (nbuf != InvalidBuffer)
_bt_relbuf(rel, nbuf);
/* Tell _bt_doinsert to wait... */
*speculativeToken = SnapshotDirty.speculativeToken;
/* Caller releases lock on buf immediately */
insertstate->bounds_valid = false;
return xwait;
}
/*
* Otherwise we have a definite conflict. But before
* complaining, look to see if the tuple we want to insert
* is itself now committed dead --- if so, don't complain.
* This is a waste of time in normal scenarios but we must
* do it to support CREATE INDEX CONCURRENTLY.
*
* We must follow HOT-chains here because during
* concurrent index build, we insert the root TID though
* the actual tuple may be somewhere in the HOT-chain.
* While following the chain we might not stop at the
* exact tuple which triggered the insert, but that's OK
* because if we find a live tuple anywhere in this chain,
* we have a unique key conflict. The other live tuple is
* not part of this chain because it had a different index
* entry.
*/
htid = itup->t_tid;
if (table_index_fetch_tuple_check(heapRel, &htid,
SnapshotSelf, NULL))
{
/* Normal case --- it's still live */
}
else
{
/*
* It's been deleted, so no error, and no need to
* continue searching
*/
break;
}
/*
* Check for a conflict-in as we would if we were going to
* write to this page. We aren't actually going to write,
* but we want a chance to report SSI conflicts that would
* otherwise be masked by this unique constraint
* violation.
*/
CheckForSerializableConflictIn(rel, NULL, BufferGetBlockNumber(insertstate->buf));
/*
* This is a definite conflict. Break the tuple down into
* datums and report the error. But first, make sure we
* release the buffer locks we're holding ---
* BuildIndexValueDescription could make catalog accesses,
* which in the worst case might touch this same index and
* cause deadlocks.
*/
if (nbuf != InvalidBuffer)
_bt_relbuf(rel, nbuf);
_bt_relbuf(rel, insertstate->buf);
insertstate->buf = InvalidBuffer;
insertstate->bounds_valid = false;
{
Datum values[INDEX_MAX_KEYS];
bool isnull[INDEX_MAX_KEYS];
char *key_desc;
index_deform_tuple(itup, RelationGetDescr(rel),
values, isnull);
key_desc = BuildIndexValueDescription(rel, values,
isnull);
ereport(ERROR,
(errcode(ERRCODE_UNIQUE_VIOLATION),
errmsg("duplicate key value violates unique constraint \"%s\"",
RelationGetRelationName(rel)),
key_desc ? errdetail("Key %s already exists.",
key_desc) : 0,
errtableconstraint(heapRel,
RelationGetRelationName(rel))));
}
}
else if (all_dead && (!inposting ||
(prevalldead &&
curposti == BTreeTupleGetNPosting(curitup) - 1)))
{
/*
* The conflicting tuple (or all HOT chains pointed to by
* all posting list TIDs) is dead to everyone, so mark the
* index entry killed.
*/
ItemIdMarkDead(curitemid);
opaque->btpo_flags |= BTP_HAS_GARBAGE;
/*
* Mark buffer with a dirty hint, since state is not
* crucial. Be sure to mark the proper buffer dirty.
*/
if (nbuf != InvalidBuffer)
MarkBufferDirtyHint(nbuf, true);
else
MarkBufferDirtyHint(insertstate->buf, true);
}
/*
* Remember if posting list tuple has even a single HOT chain
* whose members are not all dead
*/
if (!all_dead && inposting)
prevalldead = false;
}
}
if (inposting && curposti < BTreeTupleGetNPosting(curitup) - 1)
{
/* Advance to next TID in same posting list */
curposti++;
continue;
}
else if (offset < maxoff)
{
/* Advance to next tuple */
curposti = 0;
inposting = false;
offset = OffsetNumberNext(offset);
}
else
{
int highkeycmp;
/* If scankey == hikey we gotta check the next page too */
if (P_RIGHTMOST(opaque))
break;
highkeycmp = _bt_compare(rel, itup_key, page, P_HIKEY);
Assert(highkeycmp <= 0);
if (highkeycmp != 0)
break;
/* Advance to next non-dead page --- there must be one */
for (;;)
{
BlockNumber nblkno = opaque->btpo_next;
nbuf = _bt_relandgetbuf(rel, nbuf, nblkno, BT_READ);
page = BufferGetPage(nbuf);
opaque = BTPageGetOpaque(page);
if (!P_IGNORE(opaque))
break;
if (P_RIGHTMOST(opaque))
elog(ERROR, "fell off the end of index \"%s\"",
RelationGetRelationName(rel));
}
/* Will also advance to next tuple */
curposti = 0;
inposting = false;
maxoff = PageGetMaxOffsetNumber(page);
offset = P_FIRSTDATAKEY(opaque);
/* Don't invalidate binary search bounds */
}
}
/*
* If we are doing a recheck then we should have found the tuple we are
* checking. Otherwise there's something very wrong --- probably, the
* index is on a non-immutable expression.
*/
if (checkUnique == UNIQUE_CHECK_EXISTING && !found)
ereport(ERROR,
(errcode(ERRCODE_INTERNAL_ERROR),
errmsg("failed to re-find tuple within index \"%s\"",
RelationGetRelationName(rel)),
errhint("This may be because of a non-immutable index expression."),
errtableconstraint(heapRel,
RelationGetRelationName(rel))));
if (nbuf != InvalidBuffer)
_bt_relbuf(rel, nbuf);
return InvalidTransactionId;
}
/*
* _bt_findinsertloc() -- Finds an insert location for a tuple
*
* On entry, insertstate buffer contains the page the new tuple belongs
* on. It is exclusive-locked and pinned by the caller.
*
* If 'checkingunique' is true, the buffer on entry is the first page
* that contains duplicates of the new key. If there are duplicates on
* multiple pages, the correct insertion position might be some page to
* the right, rather than the first page. In that case, this function
* moves right to the correct target page.
*
* (In a !heapkeyspace index, there can be multiple pages with the same
* high key, where the new tuple could legitimately be placed on. In
* that case, the caller passes the first page containing duplicates,
* just like when checkingunique=true. If that page doesn't have enough
* room for the new tuple, this function moves right, trying to find a
* legal page that does.)
*
* If 'indexUnchanged' is true, this is for an UPDATE that didn't
* logically change the indexed value, but must nevertheless have a new
* entry to point to a successor version. This hint from the executor
* will influence our behavior when the page might have to be split and
* we must consider our options. Bottom-up index deletion can avoid
* pathological version-driven page splits, but we only want to go to the
* trouble of trying it when we already have moderate confidence that
* it's appropriate. The hint should not significantly affect our
* behavior over time unless practically all inserts on to the leaf page
* get the hint.
*
* On exit, insertstate buffer contains the chosen insertion page, and
* the offset within that page is returned. If _bt_findinsertloc needed
* to move right, the lock and pin on the original page are released, and
* the new buffer is exclusively locked and pinned instead.
*
* If insertstate contains cached binary search bounds, we will take
* advantage of them. This avoids repeating comparisons that we made in
* _bt_check_unique() already.
*/
static OffsetNumber
_bt_findinsertloc(Relation rel,
BTInsertState insertstate,
bool checkingunique,
bool indexUnchanged,
BTStack stack,
Relation heapRel)
{
BTScanInsert itup_key = insertstate->itup_key;
Page page = BufferGetPage(insertstate->buf);
BTPageOpaque opaque;
OffsetNumber newitemoff;
opaque = BTPageGetOpaque(page);
/* Check 1/3 of a page restriction */
if (unlikely(insertstate->itemsz > BTMaxItemSize(page)))
_bt_check_third_page(rel, heapRel, itup_key->heapkeyspace, page,
insertstate->itup);
Assert(P_ISLEAF(opaque) && !P_INCOMPLETE_SPLIT(opaque));
Assert(!insertstate->bounds_valid || checkingunique);
Assert(!itup_key->heapkeyspace || itup_key->scantid != NULL);
Assert(itup_key->heapkeyspace || itup_key->scantid == NULL);
Assert(!itup_key->allequalimage || itup_key->heapkeyspace);
if (itup_key->heapkeyspace)
{
/* Keep track of whether checkingunique duplicate seen */
bool uniquedup = indexUnchanged;
/*
* If we're inserting into a unique index, we may have to walk right
* through leaf pages to find the one leaf page that we must insert on
* to.
*
* This is needed for checkingunique callers because a scantid was not
* used when we called _bt_search(). scantid can only be set after
* _bt_check_unique() has checked for duplicates. The buffer
* initially stored in insertstate->buf has the page where the first
* duplicate key might be found, which isn't always the page that new
* tuple belongs on. The heap TID attribute for new tuple (scantid)
* could force us to insert on a sibling page, though that should be
* very rare in practice.
*/
if (checkingunique)
{
if (insertstate->low < insertstate->stricthigh)
{
/* Encountered a duplicate in _bt_check_unique() */
Assert(insertstate->bounds_valid);
uniquedup = true;
}
for (;;)
{
/*
* Does the new tuple belong on this page?
*
* The earlier _bt_check_unique() call may well have
* established a strict upper bound on the offset for the new
* item. If it's not the last item of the page (i.e. if there
* is at least one tuple on the page that goes after the tuple
* we're inserting) then we know that the tuple belongs on
* this page. We can skip the high key check.
*/
if (insertstate->bounds_valid &&
insertstate->low <= insertstate->stricthigh &&
insertstate->stricthigh <= PageGetMaxOffsetNumber(page))
break;
/* Test '<=', not '!=', since scantid is set now */
if (P_RIGHTMOST(opaque) ||
_bt_compare(rel, itup_key, page, P_HIKEY) <= 0)
break;
_bt_stepright(rel, heapRel, insertstate, stack);
/* Update local state after stepping right */
page = BufferGetPage(insertstate->buf);
opaque = BTPageGetOpaque(page);
/* Assume duplicates (if checkingunique) */
uniquedup = true;
}
}
/*
* If the target page cannot fit newitem, try to avoid splitting the
* page on insert by performing deletion or deduplication now
*/
if (PageGetFreeSpace(page) < insertstate->itemsz)
_bt_delete_or_dedup_one_page(rel, heapRel, insertstate, false,
checkingunique, uniquedup,
indexUnchanged);
}
else
{
/*----------
* This is a !heapkeyspace (version 2 or 3) index. The current page
* is the first page that we could insert the new tuple to, but there
* may be other pages to the right that we could opt to use instead.
*
* If the new key is equal to one or more existing keys, we can
* legitimately place it anywhere in the series of equal keys. In
* fact, if the new key is equal to the page's "high key" we can place
* it on the next page. If it is equal to the high key, and there's
* not room to insert the new tuple on the current page without
* splitting, then we move right hoping to find more free space and
* avoid a split.
*
* Keep scanning right until we
* (a) find a page with enough free space,
* (b) reach the last page where the tuple can legally go, or
* (c) get tired of searching.
* (c) is not flippant; it is important because if there are many
* pages' worth of equal keys, it's better to split one of the early
* pages than to scan all the way to the end of the run of equal keys
* on every insert. We implement "get tired" as a random choice,
* since stopping after scanning a fixed number of pages wouldn't work
* well (we'd never reach the right-hand side of previously split
* pages). The probability of moving right is set at 0.99, which may
* seem too high to change the behavior much, but it does an excellent
* job of preventing O(N^2) behavior with many equal keys.
*----------
*/
while (PageGetFreeSpace(page) < insertstate->itemsz)
{
/*
* Before considering moving right, see if we can obtain enough
* space by erasing LP_DEAD items
*/
if (P_HAS_GARBAGE(opaque))
{
/* Perform simple deletion */
_bt_delete_or_dedup_one_page(rel, heapRel, insertstate, true,
false, false, false);
if (PageGetFreeSpace(page) >= insertstate->itemsz)
break; /* OK, now we have enough space */
}
/*
* Nope, so check conditions (b) and (c) enumerated above
*
* The earlier _bt_check_unique() call may well have established a
* strict upper bound on the offset for the new item. If it's not
* the last item of the page (i.e. if there is at least one tuple
* on the page that's greater than the tuple we're inserting to)
* then we know that the tuple belongs on this page. We can skip
* the high key check.
*/
if (insertstate->bounds_valid &&
insertstate->low <= insertstate->stricthigh &&
insertstate->stricthigh <= PageGetMaxOffsetNumber(page))
break;
if (P_RIGHTMOST(opaque) ||
_bt_compare(rel, itup_key, page, P_HIKEY) != 0 ||
pg_prng_uint32(&pg_global_prng_state) <= (PG_UINT32_MAX / 100))
break;
_bt_stepright(rel, heapRel, insertstate, stack);
/* Update local state after stepping right */
page = BufferGetPage(insertstate->buf);
opaque = BTPageGetOpaque(page);
}
}
/*
* We should now be on the correct page. Find the offset within the page
* for the new tuple. (Possibly reusing earlier search bounds.)
*/
Assert(P_RIGHTMOST(opaque) ||
_bt_compare(rel, itup_key, page, P_HIKEY) <= 0);
newitemoff = _bt_binsrch_insert(rel, insertstate);
if (insertstate->postingoff == -1)
{
/*
* There is an overlapping posting list tuple with its LP_DEAD bit
* set. We don't want to unnecessarily unset its LP_DEAD bit while
* performing a posting list split, so perform simple index tuple
* deletion early.
*/
_bt_delete_or_dedup_one_page(rel, heapRel, insertstate, true,
false, false, false);
/*
* Do new binary search. New insert location cannot overlap with any
* posting list now.
*/
Assert(!insertstate->bounds_valid);
insertstate->postingoff = 0;
newitemoff = _bt_binsrch_insert(rel, insertstate);
Assert(insertstate->postingoff == 0);
}
return newitemoff;
}
/*
* Step right to next non-dead page, during insertion.
*
* This is a bit more complicated than moving right in a search. We must
* write-lock the target page before releasing write lock on current page;
* else someone else's _bt_check_unique scan could fail to see our insertion.
* Write locks on intermediate dead pages won't do because we don't know when
* they will get de-linked from the tree.
*
* This is more aggressive than it needs to be for non-unique !heapkeyspace
* indexes.
*/
static void
_bt_stepright(Relation rel, Relation heaprel, BTInsertState insertstate,
BTStack stack)
{
Page page;
BTPageOpaque opaque;
Buffer rbuf;
BlockNumber rblkno;
Assert(heaprel != NULL);
page = BufferGetPage(insertstate->buf);
opaque = BTPageGetOpaque(page);
rbuf = InvalidBuffer;
rblkno = opaque->btpo_next;
for (;;)
{
rbuf = _bt_relandgetbuf(rel, rbuf, rblkno, BT_WRITE);
page = BufferGetPage(rbuf);
opaque = BTPageGetOpaque(page);
/*
* If this page was incompletely split, finish the split now. We do
* this while holding a lock on the left sibling, which is not good
* because finishing the split could be a fairly lengthy operation.
* But this should happen very seldom.
*/
if (P_INCOMPLETE_SPLIT(opaque))
{
_bt_finish_split(rel, heaprel, rbuf, stack);
rbuf = InvalidBuffer;
continue;
}
if (!P_IGNORE(opaque))
break;
if (P_RIGHTMOST(opaque))
elog(ERROR, "fell off the end of index \"%s\"",
RelationGetRelationName(rel));
rblkno = opaque->btpo_next;
}
/* rbuf locked; unlock buf, update state for caller */
_bt_relbuf(rel, insertstate->buf);
insertstate->buf = rbuf;
insertstate->bounds_valid = false;
}
/*----------
* _bt_insertonpg() -- Insert a tuple on a particular page in the index.
*
* This recursive procedure does the following things:
*
* + if postingoff != 0, splits existing posting list tuple
* (since it overlaps with new 'itup' tuple).
* + if necessary, splits the target page, using 'itup_key' for
* suffix truncation on leaf pages (caller passes NULL for
* non-leaf pages).
* + inserts the new tuple (might be split from posting list).
* + if the page was split, pops the parent stack, and finds the
* right place to insert the new child pointer (by walking
* right using information stored in the parent stack).
* + invokes itself with the appropriate tuple for the right
* child page on the parent.
* + updates the metapage if a true root or fast root is split.
*
* On entry, we must have the correct buffer in which to do the
* insertion, and the buffer must be pinned and write-locked. On return,
* we will have dropped both the pin and the lock on the buffer.
*
* This routine only performs retail tuple insertions. 'itup' should
* always be either a non-highkey leaf item, or a downlink (new high
* key items are created indirectly, when a page is split). When
* inserting to a non-leaf page, 'cbuf' is the left-sibling of the page
* we're inserting the downlink for. This function will clear the
* INCOMPLETE_SPLIT flag on it, and release the buffer.
*----------
*/
static void
_bt_insertonpg(Relation rel,
Relation heaprel,
BTScanInsert itup_key,
Buffer buf,
Buffer cbuf,
BTStack stack,
IndexTuple itup,
Size itemsz,
OffsetNumber newitemoff,
int postingoff,
bool split_only_page)
{
Page page;
BTPageOpaque opaque;
bool isleaf,
isroot,
isrightmost,
isonly;
IndexTuple oposting = NULL;
IndexTuple origitup = NULL;
IndexTuple nposting = NULL;
page = BufferGetPage(buf);
opaque = BTPageGetOpaque(page);
isleaf = P_ISLEAF(opaque);
isroot = P_ISROOT(opaque);
isrightmost = P_RIGHTMOST(opaque);
isonly = P_LEFTMOST(opaque) && P_RIGHTMOST(opaque);
/* child buffer must be given iff inserting on an internal page */
Assert(isleaf == !BufferIsValid(cbuf));
/* tuple must have appropriate number of attributes */
Assert(!isleaf ||
BTreeTupleGetNAtts(itup, rel) ==
IndexRelationGetNumberOfAttributes(rel));
Assert(isleaf ||
BTreeTupleGetNAtts(itup, rel) <=
IndexRelationGetNumberOfKeyAttributes(rel));
Assert(!BTreeTupleIsPosting(itup));
Assert(MAXALIGN(IndexTupleSize(itup)) == itemsz);
/* Caller must always finish incomplete split for us */
Assert(!P_INCOMPLETE_SPLIT(opaque));
/*
* Every internal page should have exactly one negative infinity item at
* all times. Only _bt_split() and _bt_newlevel() should add items that
* become negative infinity items through truncation, since they're the
* only routines that allocate new internal pages.
*/
Assert(isleaf || newitemoff > P_FIRSTDATAKEY(opaque));
/*
* Do we need to split an existing posting list item?
*/
if (postingoff != 0)
{
ItemId itemid = PageGetItemId(page, newitemoff);
/*
* The new tuple is a duplicate with a heap TID that falls inside the
* range of an existing posting list tuple on a leaf page. Prepare to
* split an existing posting list. Overwriting the posting list with
* its post-split version is treated as an extra step in either the
* insert or page split critical section.
*/
Assert(isleaf && itup_key->heapkeyspace && itup_key->allequalimage);
oposting = (IndexTuple) PageGetItem(page, itemid);
/*
* postingoff value comes from earlier call to _bt_binsrch_posting().
* Its binary search might think that a plain tuple must be a posting
* list tuple that needs to be split. This can happen with corruption
* involving an existing plain tuple that is a duplicate of the new
* item, up to and including its table TID. Check for that here in
* passing.
*
* Also verify that our caller has made sure that the existing posting
* list tuple does not have its LP_DEAD bit set.
*/
if (!BTreeTupleIsPosting(oposting) || ItemIdIsDead(itemid))
ereport(ERROR,
(errcode(ERRCODE_INDEX_CORRUPTED),
errmsg_internal("table tid from new index tuple (%u,%u) overlaps with invalid duplicate tuple at offset %u of block %u in index \"%s\"",
ItemPointerGetBlockNumber(&itup->t_tid),
ItemPointerGetOffsetNumber(&itup->t_tid),
newitemoff, BufferGetBlockNumber(buf),
RelationGetRelationName(rel))));
/* use a mutable copy of itup as our itup from here on */
origitup = itup;
itup = CopyIndexTuple(origitup);
nposting = _bt_swap_posting(itup, oposting, postingoff);
/* itup now contains rightmost/max TID from oposting */
/* Alter offset so that newitem goes after posting list */
newitemoff = OffsetNumberNext(newitemoff);
}
/*
* Do we need to split the page to fit the item on it?
*
* Note: PageGetFreeSpace() subtracts sizeof(ItemIdData) from its result,
* so this comparison is correct even though we appear to be accounting
* only for the item and not for its line pointer.
*/
if (PageGetFreeSpace(page) < itemsz)
{
Buffer rbuf;
Assert(!split_only_page);
/* split the buffer into left and right halves */
rbuf = _bt_split(rel, heaprel, itup_key, buf, cbuf, newitemoff, itemsz,
itup, origitup, nposting, postingoff);
PredicateLockPageSplit(rel,
BufferGetBlockNumber(buf),
BufferGetBlockNumber(rbuf));
/*----------
* By here,
*
* + our target page has been split;
* + the original tuple has been inserted;
* + we have write locks on both the old (left half)
* and new (right half) buffers, after the split; and
* + we know the key we want to insert into the parent
* (it's the "high key" on the left child page).
*
* We're ready to do the parent insertion. We need to hold onto the
* locks for the child pages until we locate the parent, but we can
* at least release the lock on the right child before doing the
* actual insertion. The lock on the left child will be released
* last of all by parent insertion, where it is the 'cbuf' of parent
* page.
*----------
*/
_bt_insert_parent(rel, heaprel, buf, rbuf, stack, isroot, isonly);
}
else
{
Buffer metabuf = InvalidBuffer;
Page metapg = NULL;
BTMetaPageData *metad = NULL;
BlockNumber blockcache;
/*
* If we are doing this insert because we split a page that was the
* only one on its tree level, but was not the root, it may have been
* the "fast root". We need to ensure that the fast root link points
* at or above the current page. We can safely acquire a lock on the
* metapage here --- see comments for _bt_newlevel().
*/
if (unlikely(split_only_page))
{
Assert(!isleaf);
Assert(BufferIsValid(cbuf));
metabuf = _bt_getbuf(rel, BTREE_METAPAGE, BT_WRITE);
metapg = BufferGetPage(metabuf);
metad = BTPageGetMeta(metapg);
if (metad->btm_fastlevel >= opaque->btpo_level)
{
/* no update wanted */
_bt_relbuf(rel, metabuf);
metabuf = InvalidBuffer;
}
}
/* Do the update. No ereport(ERROR) until changes are logged */
START_CRIT_SECTION();
if (postingoff != 0)
memcpy(oposting, nposting, MAXALIGN(IndexTupleSize(nposting)));
if (PageAddItem(page, (Item) itup, itemsz, newitemoff, false,
false) == InvalidOffsetNumber)
elog(PANIC, "failed to add new item to block %u in index \"%s\"",
BufferGetBlockNumber(buf), RelationGetRelationName(rel));
MarkBufferDirty(buf);
if (BufferIsValid(metabuf))
{
/* upgrade meta-page if needed */
if (metad->btm_version < BTREE_NOVAC_VERSION)
_bt_upgrademetapage(metapg);
metad->btm_fastroot = BufferGetBlockNumber(buf);
metad->btm_fastlevel = opaque->btpo_level;
MarkBufferDirty(metabuf);
}
/*
* Clear INCOMPLETE_SPLIT flag on child if inserting the new item
* finishes a split
*/
if (!isleaf)
{
Page cpage = BufferGetPage(cbuf);
BTPageOpaque cpageop = BTPageGetOpaque(cpage);
Assert(P_INCOMPLETE_SPLIT(cpageop));
cpageop->btpo_flags &= ~BTP_INCOMPLETE_SPLIT;
MarkBufferDirty(cbuf);
}
/* XLOG stuff */
if (RelationNeedsWAL(rel))
{
xl_btree_insert xlrec;
xl_btree_metadata xlmeta;
uint8 xlinfo;
XLogRecPtr recptr;
uint16 upostingoff;
xlrec.offnum = newitemoff;
XLogBeginInsert();
XLogRegisterData((char *) &xlrec, SizeOfBtreeInsert);
if (isleaf && postingoff == 0)
{
/* Simple leaf insert */
xlinfo = XLOG_BTREE_INSERT_LEAF;
}
else if (postingoff != 0)
{
/*
* Leaf insert with posting list split. Must include
* postingoff field before newitem/orignewitem.
*/
Assert(isleaf);
xlinfo = XLOG_BTREE_INSERT_POST;
}
else
{
/* Internal page insert, which finishes a split on cbuf */
xlinfo = XLOG_BTREE_INSERT_UPPER;
XLogRegisterBuffer(1, cbuf, REGBUF_STANDARD);
if (BufferIsValid(metabuf))
{
/* Actually, it's an internal page insert + meta update */
xlinfo = XLOG_BTREE_INSERT_META;
Assert(metad->btm_version >= BTREE_NOVAC_VERSION);
xlmeta.version = metad->btm_version;
xlmeta.root = metad->btm_root;
xlmeta.level = metad->btm_level;
xlmeta.fastroot = metad->btm_fastroot;
xlmeta.fastlevel = metad->btm_fastlevel;
xlmeta.last_cleanup_num_delpages = metad->btm_last_cleanup_num_delpages;
xlmeta.allequalimage = metad->btm_allequalimage;
XLogRegisterBuffer(2, metabuf,
REGBUF_WILL_INIT | REGBUF_STANDARD);
XLogRegisterBufData(2, (char *) &xlmeta,
sizeof(xl_btree_metadata));
}
}
XLogRegisterBuffer(0, buf, REGBUF_STANDARD);
if (postingoff == 0)
{
/* Just log itup from caller */
XLogRegisterBufData(0, (char *) itup, IndexTupleSize(itup));
}
else
{
/*
* Insert with posting list split (XLOG_BTREE_INSERT_POST
* record) case.
*
* Log postingoff. Also log origitup, not itup. REDO routine
* must reconstruct final itup (as well as nposting) using
* _bt_swap_posting().
*/
upostingoff = postingoff;
XLogRegisterBufData(0, (char *) &upostingoff, sizeof(uint16));
XLogRegisterBufData(0, (char *) origitup,
IndexTupleSize(origitup));
}
recptr = XLogInsert(RM_BTREE_ID, xlinfo);
if (BufferIsValid(metabuf))
PageSetLSN(metapg, recptr);
if (!isleaf)
PageSetLSN(BufferGetPage(cbuf), recptr);
PageSetLSN(page, recptr);
}
END_CRIT_SECTION();
/* Release subsidiary buffers */
if (BufferIsValid(metabuf))
_bt_relbuf(rel, metabuf);
if (!isleaf)
_bt_relbuf(rel, cbuf);
/*
* Cache the block number if this is the rightmost leaf page. Cache
* may be used by a future inserter within _bt_search_insert().
*/
blockcache = InvalidBlockNumber;
if (isrightmost && isleaf && !isroot)
blockcache = BufferGetBlockNumber(buf);
/* Release buffer for insertion target block */
_bt_relbuf(rel, buf);
/*
* If we decided to cache the insertion target block before releasing
* its buffer lock, then cache it now. Check the height of the tree
* first, though. We don't go for the optimization with small
* indexes. Defer final check to this point to ensure that we don't
* call _bt_getrootheight while holding a buffer lock.
*/
if (BlockNumberIsValid(blockcache) &&
_bt_getrootheight(rel) >= BTREE_FASTPATH_MIN_LEVEL)
RelationSetTargetBlock(rel, blockcache);
}
/* be tidy */
if (postingoff != 0)
{
/* itup is actually a modified copy of caller's original */
pfree(nposting);
pfree(itup);
}
}
/*
* _bt_split() -- split a page in the btree.
*
* On entry, buf is the page to split, and is pinned and write-locked.
* newitemoff etc. tell us about the new item that must be inserted
* along with the data from the original page.
*
* itup_key is used for suffix truncation on leaf pages (internal
* page callers pass NULL). When splitting a non-leaf page, 'cbuf'
* is the left-sibling of the page we're inserting the downlink for.
* This function will clear the INCOMPLETE_SPLIT flag on it, and
* release the buffer.
*
* orignewitem, nposting, and postingoff are needed when an insert of
* orignewitem results in both a posting list split and a page split.
* These extra posting list split details are used here in the same
* way as they are used in the more common case where a posting list
* split does not coincide with a page split. We need to deal with
* posting list splits directly in order to ensure that everything
* that follows from the insert of orignewitem is handled as a single
* atomic operation (though caller's insert of a new pivot/downlink
* into parent page will still be a separate operation). See
* nbtree/README for details on the design of posting list splits.
*
* Returns the new right sibling of buf, pinned and write-locked.
* The pin and lock on buf are maintained.
*/
static Buffer
_bt_split(Relation rel, Relation heaprel, BTScanInsert itup_key, Buffer buf,
Buffer cbuf, OffsetNumber newitemoff, Size newitemsz, IndexTuple newitem,
IndexTuple orignewitem, IndexTuple nposting, uint16 postingoff)
{
Buffer rbuf;
Page origpage;
Page leftpage,
rightpage;
BlockNumber origpagenumber,
rightpagenumber;
BTPageOpaque ropaque,
lopaque,
oopaque;
Buffer sbuf = InvalidBuffer;
Page spage = NULL;
BTPageOpaque sopaque = NULL;
Size itemsz;
ItemId itemid;
IndexTuple firstright,
lefthighkey;
OffsetNumber firstrightoff;
OffsetNumber afterleftoff,
afterrightoff,
minusinfoff;
OffsetNumber origpagepostingoff;
OffsetNumber maxoff;
OffsetNumber i;
bool newitemonleft,
isleaf,
isrightmost;
/*
* origpage is the original page to be split. leftpage is a temporary
* buffer that receives the left-sibling data, which will be copied back
* into origpage on success. rightpage is the new page that will receive
* the right-sibling data.
*
* leftpage is allocated after choosing a split point. rightpage's new
* buffer isn't acquired until after leftpage is initialized and has new
* high key, the last point where splitting the page may fail (barring
* corruption). Failing before acquiring new buffer won't have lasting
* consequences, since origpage won't have been modified and leftpage is
* only workspace.
*/
origpage = BufferGetPage(buf);
oopaque = BTPageGetOpaque(origpage);
isleaf = P_ISLEAF(oopaque);
isrightmost = P_RIGHTMOST(oopaque);
maxoff = PageGetMaxOffsetNumber(origpage);
origpagenumber = BufferGetBlockNumber(buf);
/*
* Choose a point to split origpage at.
*
* A split point can be thought of as a point _between_ two existing data
* items on origpage (the lastleft and firstright tuples), provided you
* pretend that the new item that didn't fit is already on origpage.
*
* Since origpage does not actually contain newitem, the representation of
* split points needs to work with two boundary cases: splits where
* newitem is lastleft, and splits where newitem is firstright.
* newitemonleft resolves the ambiguity that would otherwise exist when
* newitemoff == firstrightoff. In all other cases it's clear which side
* of the split every tuple goes on from context. newitemonleft is
* usually (but not always) redundant information.
*
* firstrightoff is supposed to be an origpage offset number, but it's
* possible that its value will be maxoff+1, which is "past the end" of
* origpage. This happens in the rare case where newitem goes after all
* existing items (i.e. newitemoff is maxoff+1) and we end up splitting
* origpage at the point that leaves newitem alone on new right page. Any
* "!newitemonleft && newitemoff == firstrightoff" split point makes
* newitem the firstright tuple, though, so this case isn't a special
* case.
*/
firstrightoff = _bt_findsplitloc(rel, origpage, newitemoff, newitemsz,
newitem, &newitemonleft);
/* Allocate temp buffer for leftpage */
leftpage = PageGetTempPage(origpage);
_bt_pageinit(leftpage, BufferGetPageSize(buf));
lopaque = BTPageGetOpaque(leftpage);
/*
* leftpage won't be the root when we're done. Also, clear the SPLIT_END
* and HAS_GARBAGE flags.
*/
lopaque->btpo_flags = oopaque->btpo_flags;
lopaque->btpo_flags &= ~(BTP_ROOT | BTP_SPLIT_END | BTP_HAS_GARBAGE);
/* set flag in leftpage indicating that rightpage has no downlink yet */
lopaque->btpo_flags |= BTP_INCOMPLETE_SPLIT;
lopaque->btpo_prev = oopaque->btpo_prev;
/* handle btpo_next after rightpage buffer acquired */
lopaque->btpo_level = oopaque->btpo_level;
/* handle btpo_cycleid after rightpage buffer acquired */
/*
* Copy the original page's LSN into leftpage, which will become the
* updated version of the page. We need this because XLogInsert will
* examine the LSN and possibly dump it in a page image.
*/
PageSetLSN(leftpage, PageGetLSN(origpage));
/*
* Determine page offset number of existing overlapped-with-orignewitem
* posting list when it is necessary to perform a posting list split in
* passing. Note that newitem was already changed by caller (newitem no
* longer has the orignewitem TID).
*
* This page offset number (origpagepostingoff) will be used to pretend
* that the posting split has already taken place, even though the
* required modifications to origpage won't occur until we reach the
* critical section. The lastleft and firstright tuples of our page split
* point should, in effect, come from an imaginary version of origpage
* that has the nposting tuple instead of the original posting list tuple.
*
* Note: _bt_findsplitloc() should have compensated for coinciding posting
* list splits in just the same way, at least in theory. It doesn't
* bother with that, though. In practice it won't affect its choice of
* split point.
*/
origpagepostingoff = InvalidOffsetNumber;
if (postingoff != 0)
{
Assert(isleaf);
Assert(ItemPointerCompare(&orignewitem->t_tid,
&newitem->t_tid) < 0);
Assert(BTreeTupleIsPosting(nposting));
origpagepostingoff = OffsetNumberPrev(newitemoff);
}
/*
* The high key for the new left page is a possibly-truncated copy of
* firstright on the leaf level (it's "firstright itself" on internal
* pages; see !isleaf comments below). This may seem to be contrary to
* Lehman & Yao's approach of using a copy of lastleft as the new high key
* when splitting on the leaf level. It isn't, though.
*
* Suffix truncation will leave the left page's high key fully equal to
* lastleft when lastleft and firstright are equal prior to heap TID (that
* is, the tiebreaker TID value comes from lastleft). It isn't actually
* necessary for a new leaf high key to be a copy of lastleft for the L&Y
* "subtree" invariant to hold. It's sufficient to make sure that the new
* leaf high key is strictly less than firstright, and greater than or
* equal to (not necessarily equal to) lastleft. In other words, when
* suffix truncation isn't possible during a leaf page split, we take
* L&Y's exact approach to generating a new high key for the left page.
* (Actually, that is slightly inaccurate. We don't just use a copy of
* lastleft. A tuple with all the keys from firstright but the max heap
* TID from lastleft is used, to avoid introducing a special case.)
*/
if (!newitemonleft && newitemoff == firstrightoff)
{
/* incoming tuple becomes firstright */
itemsz = newitemsz;
firstright = newitem;
}
else
{
/* existing item at firstrightoff becomes firstright */
itemid = PageGetItemId(origpage, firstrightoff);
itemsz = ItemIdGetLength(itemid);
firstright = (IndexTuple) PageGetItem(origpage, itemid);
if (firstrightoff == origpagepostingoff)
firstright = nposting;
}
if (isleaf)
{
IndexTuple lastleft;
/* Attempt suffix truncation for leaf page splits */
if (newitemonleft && newitemoff == firstrightoff)
{
/* incoming tuple becomes lastleft */
lastleft = newitem;
}
else
{
OffsetNumber lastleftoff;
/* existing item before firstrightoff becomes lastleft */
lastleftoff = OffsetNumberPrev(firstrightoff);
Assert(lastleftoff >= P_FIRSTDATAKEY(oopaque));
itemid = PageGetItemId(origpage, lastleftoff);
lastleft = (IndexTuple) PageGetItem(origpage, itemid);
if (lastleftoff == origpagepostingoff)
lastleft = nposting;
}
lefthighkey = _bt_truncate(rel, lastleft, firstright, itup_key);
itemsz = IndexTupleSize(lefthighkey);
}
else
{
/*
* Don't perform suffix truncation on a copy of firstright to make
* left page high key for internal page splits. Must use firstright
* as new high key directly.
*
* Each distinct separator key value originates as a leaf level high
* key; all other separator keys/pivot tuples are copied from one
* level down. A separator key in a grandparent page must be
* identical to high key in rightmost parent page of the subtree to
* its left, which must itself be identical to high key in rightmost
* child page of that same subtree (this even applies to separator
* from grandparent's high key). There must always be an unbroken
* "seam" of identical separator keys that guide index scans at every
* level, starting from the grandparent. That's why suffix truncation
* is unsafe here.
*
* Internal page splits will truncate firstright into a "negative
* infinity" data item when it gets inserted on the new right page
* below, though. This happens during the call to _bt_pgaddtup() for
* the new first data item for right page. Do not confuse this
* mechanism with suffix truncation. It is just a convenient way of
* implementing page splits that split the internal page "inside"
* firstright. The lefthighkey separator key cannot appear a second
* time in the right page (only firstright's downlink goes in right
* page).
*/
lefthighkey = firstright;
}
/*
* Add new high key to leftpage
*/
afterleftoff = P_HIKEY;
Assert(BTreeTupleGetNAtts(lefthighkey, rel) > 0);
Assert(BTreeTupleGetNAtts(lefthighkey, rel) <=
IndexRelationGetNumberOfKeyAttributes(rel));
Assert(itemsz == MAXALIGN(IndexTupleSize(lefthighkey)));
if (PageAddItem(leftpage, (Item) lefthighkey, itemsz, afterleftoff, false,
false) == InvalidOffsetNumber)
elog(ERROR, "failed to add high key to the left sibling"
" while splitting block %u of index \"%s\"",
origpagenumber, RelationGetRelationName(rel));
afterleftoff = OffsetNumberNext(afterleftoff);
/*
* Acquire a new right page to split into, now that left page has a new
* high key. From here on, it's not okay to throw an error without
* zeroing rightpage first. This coding rule ensures that we won't
* confuse future VACUUM operations, which might otherwise try to re-find
* a downlink to a leftover junk page as the page undergoes deletion.
*
* It would be reasonable to start the critical section just after the new
* rightpage buffer is acquired instead; that would allow us to avoid
* leftover junk pages without bothering to zero rightpage. We do it this
* way because it avoids an unnecessary PANIC when either origpage or its
* existing sibling page are corrupt.
*/
rbuf = _bt_allocbuf(rel, heaprel);
rightpage = BufferGetPage(rbuf);
rightpagenumber = BufferGetBlockNumber(rbuf);
/* rightpage was initialized by _bt_getbuf */
ropaque = BTPageGetOpaque(rightpage);
/*
* Finish off remaining leftpage special area fields. They cannot be set
* before both origpage (leftpage) and rightpage buffers are acquired and
* locked.
*
* btpo_cycleid is only used with leaf pages, though we set it here in all
* cases just to be consistent.
*/
lopaque->btpo_next = rightpagenumber;
lopaque->btpo_cycleid = _bt_vacuum_cycleid(rel);
/*
* rightpage won't be the root when we're done. Also, clear the SPLIT_END
* and HAS_GARBAGE flags.
*/
ropaque->btpo_flags = oopaque->btpo_flags;
ropaque->btpo_flags &= ~(BTP_ROOT | BTP_SPLIT_END | BTP_HAS_GARBAGE);
ropaque->btpo_prev = origpagenumber;
ropaque->btpo_next = oopaque->btpo_next;
ropaque->btpo_level = oopaque->btpo_level;
ropaque->btpo_cycleid = lopaque->btpo_cycleid;
/*
* Add new high key to rightpage where necessary.
*
* If the page we're splitting is not the rightmost page at its level in
* the tree, then the first entry on the page is the high key from
* origpage.
*/
afterrightoff = P_HIKEY;
if (!isrightmost)
{
IndexTuple righthighkey;
itemid = PageGetItemId(origpage, P_HIKEY);
itemsz = ItemIdGetLength(itemid);
righthighkey = (IndexTuple) PageGetItem(origpage, itemid);
Assert(BTreeTupleGetNAtts(righthighkey, rel) > 0);
Assert(BTreeTupleGetNAtts(righthighkey, rel) <=
IndexRelationGetNumberOfKeyAttributes(rel));
if (PageAddItem(rightpage, (Item) righthighkey, itemsz, afterrightoff,
false, false) == InvalidOffsetNumber)
{
memset(rightpage, 0, BufferGetPageSize(rbuf));
elog(ERROR, "failed to add high key to the right sibling"
" while splitting block %u of index \"%s\"",
origpagenumber, RelationGetRelationName(rel));
}
afterrightoff = OffsetNumberNext(afterrightoff);
}
/*
* Internal page splits truncate first data item on right page -- it
* becomes "minus infinity" item for the page. Set this up here.
*/
minusinfoff = InvalidOffsetNumber;
if (!isleaf)
minusinfoff = afterrightoff;
/*
* Now transfer all the data items (non-pivot tuples in isleaf case, or
* additional pivot tuples in !isleaf case) to the appropriate page.
*
* Note: we *must* insert at least the right page's items in item-number
* order, for the benefit of _bt_restore_page().
*/
for (i = P_FIRSTDATAKEY(oopaque); i <= maxoff; i = OffsetNumberNext(i))
{
IndexTuple dataitem;
itemid = PageGetItemId(origpage, i);
itemsz = ItemIdGetLength(itemid);
dataitem = (IndexTuple) PageGetItem(origpage, itemid);
/* replace original item with nposting due to posting split? */
if (i == origpagepostingoff)
{
Assert(BTreeTupleIsPosting(dataitem));
Assert(itemsz == MAXALIGN(IndexTupleSize(nposting)));
dataitem = nposting;
}
/* does new item belong before this one? */
else if (i == newitemoff)
{
if (newitemonleft)
{
Assert(newitemoff <= firstrightoff);
if (!_bt_pgaddtup(leftpage, newitemsz, newitem, afterleftoff,
false))
{
memset(rightpage, 0, BufferGetPageSize(rbuf));
elog(ERROR, "failed to add new item to the left sibling"
" while splitting block %u of index \"%s\"",
origpagenumber, RelationGetRelationName(rel));
}
afterleftoff = OffsetNumberNext(afterleftoff);
}
else
{
Assert(newitemoff >= firstrightoff);
if (!_bt_pgaddtup(rightpage, newitemsz, newitem, afterrightoff,
afterrightoff == minusinfoff))
{
memset(rightpage, 0, BufferGetPageSize(rbuf));
elog(ERROR, "failed to add new item to the right sibling"
" while splitting block %u of index \"%s\"",
origpagenumber, RelationGetRelationName(rel));
}
afterrightoff = OffsetNumberNext(afterrightoff);
}
}
/* decide which page to put it on */
if (i < firstrightoff)
{
if (!_bt_pgaddtup(leftpage, itemsz, dataitem, afterleftoff, false))
{
memset(rightpage, 0, BufferGetPageSize(rbuf));
elog(ERROR, "failed to add old item to the left sibling"
" while splitting block %u of index \"%s\"",
origpagenumber, RelationGetRelationName(rel));
}
afterleftoff = OffsetNumberNext(afterleftoff);
}
else
{
if (!_bt_pgaddtup(rightpage, itemsz, dataitem, afterrightoff,
afterrightoff == minusinfoff))
{
memset(rightpage, 0, BufferGetPageSize(rbuf));
elog(ERROR, "failed to add old item to the right sibling"
" while splitting block %u of index \"%s\"",
origpagenumber, RelationGetRelationName(rel));
}
afterrightoff = OffsetNumberNext(afterrightoff);
}
}
/* Handle case where newitem goes at the end of rightpage */
if (i <= newitemoff)
{
/*
* Can't have newitemonleft here; that would imply we were told to put
* *everything* on the left page, which cannot fit (if it could, we'd
* not be splitting the page).
*/
Assert(!newitemonleft && newitemoff == maxoff + 1);
if (!_bt_pgaddtup(rightpage, newitemsz, newitem, afterrightoff,
afterrightoff == minusinfoff))
{
memset(rightpage, 0, BufferGetPageSize(rbuf));
elog(ERROR, "failed to add new item to the right sibling"
" while splitting block %u of index \"%s\"",
origpagenumber, RelationGetRelationName(rel));
}
afterrightoff = OffsetNumberNext(afterrightoff);
}
/*
* We have to grab the original right sibling (if any) and update its prev
* link. We are guaranteed that this is deadlock-free, since we couple
* the locks in the standard order: left to right.
*/
if (!isrightmost)
{
sbuf = _bt_getbuf(rel, oopaque->btpo_next, BT_WRITE);
spage = BufferGetPage(sbuf);
sopaque = BTPageGetOpaque(spage);
if (sopaque->btpo_prev != origpagenumber)
{
memset(rightpage, 0, BufferGetPageSize(rbuf));
ereport(ERROR,
(errcode(ERRCODE_INDEX_CORRUPTED),
errmsg_internal("right sibling's left-link doesn't match: "
"block %u links to %u instead of expected %u in index \"%s\"",
oopaque->btpo_next, sopaque->btpo_prev, origpagenumber,
RelationGetRelationName(rel))));
}
/*
* Check to see if we can set the SPLIT_END flag in the right-hand
* split page; this can save some I/O for vacuum since it need not
* proceed to the right sibling. We can set the flag if the right
* sibling has a different cycleid: that means it could not be part of
* a group of pages that were all split off from the same ancestor
* page. If you're confused, imagine that page A splits to A B and
* then again, yielding A C B, while vacuum is in progress. Tuples
* originally in A could now be in either B or C, hence vacuum must
* examine both pages. But if D, our right sibling, has a different
* cycleid then it could not contain any tuples that were in A when
* the vacuum started.
*/
if (sopaque->btpo_cycleid != ropaque->btpo_cycleid)
ropaque->btpo_flags |= BTP_SPLIT_END;
}
/*
* Right sibling is locked, new siblings are prepared, but original page
* is not updated yet.
*
* NO EREPORT(ERROR) till right sibling is updated. We can get away with
* not starting the critical section till here because we haven't been
* scribbling on the original page yet; see comments above.
*/
START_CRIT_SECTION();
/*
* By here, the original data page has been split into two new halves, and
* these are correct. The algorithm requires that the left page never
* move during a split, so we copy the new left page back on top of the
* original. We need to do this before writing the WAL record, so that
* XLogInsert can WAL log an image of the page if necessary.
*/
PageRestoreTempPage(leftpage, origpage);
/* leftpage, lopaque must not be used below here */
MarkBufferDirty(buf);
MarkBufferDirty(rbuf);
if (!isrightmost)
{
sopaque->btpo_prev = rightpagenumber;
MarkBufferDirty(sbuf);
}
/*
* Clear INCOMPLETE_SPLIT flag on child if inserting the new item finishes
* a split
*/
if (!isleaf)
{
Page cpage = BufferGetPage(cbuf);
BTPageOpaque cpageop = BTPageGetOpaque(cpage);
cpageop->btpo_flags &= ~BTP_INCOMPLETE_SPLIT;
MarkBufferDirty(cbuf);
}
/* XLOG stuff */
if (RelationNeedsWAL(rel))
{
xl_btree_split xlrec;
uint8 xlinfo;
XLogRecPtr recptr;
xlrec.level = ropaque->btpo_level;
/* See comments below on newitem, orignewitem, and posting lists */
xlrec.firstrightoff = firstrightoff;
xlrec.newitemoff = newitemoff;
xlrec.postingoff = 0;
if (postingoff != 0 && origpagepostingoff < firstrightoff)
xlrec.postingoff = postingoff;
XLogBeginInsert();
XLogRegisterData((char *) &xlrec, SizeOfBtreeSplit);
XLogRegisterBuffer(0, buf, REGBUF_STANDARD);
XLogRegisterBuffer(1, rbuf, REGBUF_WILL_INIT);
/* Log original right sibling, since we've changed its prev-pointer */
if (!isrightmost)
XLogRegisterBuffer(2, sbuf, REGBUF_STANDARD);
if (!isleaf)
XLogRegisterBuffer(3, cbuf, REGBUF_STANDARD);
/*
* Log the new item, if it was inserted on the left page. (If it was
* put on the right page, we don't need to explicitly WAL log it
* because it's included with all the other items on the right page.)
* Show the new item as belonging to the left page buffer, so that it
* is not stored if XLogInsert decides it needs a full-page image of
* the left page. We always store newitemoff in the record, though.
*
* The details are sometimes slightly different for page splits that
* coincide with a posting list split. If both the replacement
* posting list and newitem go on the right page, then we don't need
* to log anything extra, just like the simple !newitemonleft
* no-posting-split case (postingoff is set to zero in the WAL record,
* so recovery doesn't need to process a posting list split at all).
* Otherwise, we set postingoff and log orignewitem instead of
* newitem, despite having actually inserted newitem. REDO routine
* must reconstruct nposting and newitem using _bt_swap_posting().
*
* Note: It's possible that our page split point is the point that
* makes the posting list lastleft and newitem firstright. This is
* the only case where we log orignewitem/newitem despite newitem
* going on the right page. If XLogInsert decides that it can omit
* orignewitem due to logging a full-page image of the left page,
* everything still works out, since recovery only needs to log
* orignewitem for items on the left page (just like the regular
* newitem-logged case).
*/
if (newitemonleft && xlrec.postingoff == 0)
XLogRegisterBufData(0, (char *) newitem, newitemsz);
else if (xlrec.postingoff != 0)
{
Assert(isleaf);
Assert(newitemonleft || firstrightoff == newitemoff);
Assert(newitemsz == IndexTupleSize(orignewitem));
XLogRegisterBufData(0, (char *) orignewitem, newitemsz);
}
/* Log the left page's new high key */
if (!isleaf)
{
/* lefthighkey isn't local copy, get current pointer */
itemid = PageGetItemId(origpage, P_HIKEY);
lefthighkey = (IndexTuple) PageGetItem(origpage, itemid);
}
XLogRegisterBufData(0, (char *) lefthighkey,
MAXALIGN(IndexTupleSize(lefthighkey)));
/*
* Log the contents of the right page in the format understood by
* _bt_restore_page(). The whole right page will be recreated.
*
* Direct access to page is not good but faster - we should implement
* some new func in page API. Note we only store the tuples
* themselves, knowing that they were inserted in item-number order
* and so the line pointers can be reconstructed. See comments for
* _bt_restore_page().
*/
XLogRegisterBufData(1,
(char *) rightpage + ((PageHeader) rightpage)->pd_upper,
((PageHeader) rightpage)->pd_special - ((PageHeader) rightpage)->pd_upper);
xlinfo = newitemonleft ? XLOG_BTREE_SPLIT_L : XLOG_BTREE_SPLIT_R;
recptr = XLogInsert(RM_BTREE_ID, xlinfo);
PageSetLSN(origpage, recptr);
PageSetLSN(rightpage, recptr);
if (!isrightmost)
PageSetLSN(spage, recptr);
if (!isleaf)
PageSetLSN(BufferGetPage(cbuf), recptr);
}
END_CRIT_SECTION();
/* release the old right sibling */
if (!isrightmost)
_bt_relbuf(rel, sbuf);
/* release the child */
if (!isleaf)
_bt_relbuf(rel, cbuf);
/* be tidy */
if (isleaf)
pfree(lefthighkey);
/* split's done */
return rbuf;
}
/*
* _bt_insert_parent() -- Insert downlink into parent, completing split.
*
* On entry, buf and rbuf are the left and right split pages, which we
* still hold write locks on. Both locks will be released here. We
* release the rbuf lock once we have a write lock on the page that we
* intend to insert a downlink to rbuf on (i.e. buf's current parent page).
* The lock on buf is released at the same point as the lock on the parent
* page, since buf's INCOMPLETE_SPLIT flag must be cleared by the same
* atomic operation that completes the split by inserting a new downlink.
*
* stack - stack showing how we got here. Will be NULL when splitting true
* root, or during concurrent root split, where we can be inefficient
* isroot - we split the true root
* isonly - we split a page alone on its level (might have been fast root)
*/
static void
_bt_insert_parent(Relation rel,
Relation heaprel,
Buffer buf,
Buffer rbuf,
BTStack stack,
bool isroot,
bool isonly)
{
Assert(heaprel != NULL);
/*
* Here we have to do something Lehman and Yao don't talk about: deal with
* a root split and construction of a new root. If our stack is empty
* then we have just split a node on what had been the root level when we
* descended the tree. If it was still the root then we perform a
* new-root construction. If it *wasn't* the root anymore, search to find
* the next higher level that someone constructed meanwhile, and find the
* right place to insert as for the normal case.
*
* If we have to search for the parent level, we do so by re-descending
* from the root. This is not super-efficient, but it's rare enough not
* to matter.
*/
if (isroot)
{
Buffer rootbuf;
Assert(stack == NULL);
Assert(isonly);
/* create a new root node one level up and update the metapage */
rootbuf = _bt_newlevel(rel, heaprel, buf, rbuf);
/* release the split buffers */
_bt_relbuf(rel, rootbuf);
_bt_relbuf(rel, rbuf);
_bt_relbuf(rel, buf);
}
else
{
BlockNumber bknum = BufferGetBlockNumber(buf);
BlockNumber rbknum = BufferGetBlockNumber(rbuf);
Page page = BufferGetPage(buf);
IndexTuple new_item;
BTStackData fakestack;
IndexTuple ritem;
Buffer pbuf;
if (stack == NULL)
{
BTPageOpaque opaque;
elog(DEBUG2, "concurrent ROOT page split");
opaque = BTPageGetOpaque(page);
/*
* We should never reach here when a leaf page split takes place
* despite the insert of newitem being able to apply the fastpath
* optimization. Make sure of that with an assertion.
*
* This is more of a performance issue than a correctness issue.
* The fastpath won't have a descent stack. Using a phony stack
* here works, but never rely on that. The fastpath should be
* rejected within _bt_search_insert() when the rightmost leaf
* page will split, since it's faster to go through _bt_search()
* and get a stack in the usual way.
*/
Assert(!(P_ISLEAF(opaque) &&
BlockNumberIsValid(RelationGetTargetBlock(rel))));
/* Find the leftmost page at the next level up */
pbuf = _bt_get_endpoint(rel, opaque->btpo_level + 1, false);
/* Set up a phony stack entry pointing there */
stack = &fakestack;
stack->bts_blkno = BufferGetBlockNumber(pbuf);
stack->bts_offset = InvalidOffsetNumber;
stack->bts_parent = NULL;
_bt_relbuf(rel, pbuf);
}
/* get high key from left, a strict lower bound for new right page */
ritem = (IndexTuple) PageGetItem(page,
PageGetItemId(page, P_HIKEY));
/* form an index tuple that points at the new right page */
new_item = CopyIndexTuple(ritem);
BTreeTupleSetDownLink(new_item, rbknum);
/*
* Re-find and write lock the parent of buf.
*
* It's possible that the location of buf's downlink has changed since
* our initial _bt_search() descent. _bt_getstackbuf() will detect
* and recover from this, updating the stack, which ensures that the
* new downlink will be inserted at the correct offset. Even buf's
* parent may have changed.
*/
pbuf = _bt_getstackbuf(rel, heaprel, stack, bknum);
/*
* Unlock the right child. The left child will be unlocked in
* _bt_insertonpg().
*
* Unlocking the right child must be delayed until here to ensure that
* no concurrent VACUUM operation can become confused. Page deletion
* cannot be allowed to fail to re-find a downlink for the rbuf page.
* (Actually, this is just a vestige of how things used to work. The
* page deletion code is expected to check for the INCOMPLETE_SPLIT
* flag on the left child. It won't attempt deletion of the right
* child until the split is complete. Despite all this, we opt to
* conservatively delay unlocking the right child until here.)
*/
_bt_relbuf(rel, rbuf);
if (pbuf == InvalidBuffer)
ereport(ERROR,
(errcode(ERRCODE_INDEX_CORRUPTED),
errmsg_internal("failed to re-find parent key in index \"%s\" for split pages %u/%u",
RelationGetRelationName(rel), bknum, rbknum)));
/* Recursively insert into the parent */
_bt_insertonpg(rel, heaprel, NULL, pbuf, buf, stack->bts_parent,
new_item, MAXALIGN(IndexTupleSize(new_item)),
stack->bts_offset + 1, 0, isonly);
/* be tidy */
pfree(new_item);
}
}
/*
* _bt_finish_split() -- Finish an incomplete split
*
* A crash or other failure can leave a split incomplete. The insertion
* routines won't allow to insert on a page that is incompletely split.
* Before inserting on such a page, call _bt_finish_split().
*
* On entry, 'lbuf' must be locked in write-mode. On exit, it is unlocked
* and unpinned.
*
* Caller must provide a valid heaprel, since finishing a page split requires
* allocating a new page if and when the parent page splits in turn.
*/
void
_bt_finish_split(Relation rel, Relation heaprel, Buffer lbuf, BTStack stack)
{
Page lpage = BufferGetPage(lbuf);
BTPageOpaque lpageop = BTPageGetOpaque(lpage);
Buffer rbuf;
Page rpage;
BTPageOpaque rpageop;
bool wasroot;
bool wasonly;
Assert(P_INCOMPLETE_SPLIT(lpageop));
Assert(heaprel != NULL);
/* Lock right sibling, the one missing the downlink */
rbuf = _bt_getbuf(rel, lpageop->btpo_next, BT_WRITE);
rpage = BufferGetPage(rbuf);
rpageop = BTPageGetOpaque(rpage);
/* Could this be a root split? */
if (!stack)
{
Buffer metabuf;
Page metapg;
BTMetaPageData *metad;
/* acquire lock on the metapage */
metabuf = _bt_getbuf(rel, BTREE_METAPAGE, BT_WRITE);
metapg = BufferGetPage(metabuf);
metad = BTPageGetMeta(metapg);
wasroot = (metad->btm_root == BufferGetBlockNumber(lbuf));
_bt_relbuf(rel, metabuf);
}
else
wasroot = false;
/* Was this the only page on the level before split? */
wasonly = (P_LEFTMOST(lpageop) && P_RIGHTMOST(rpageop));
elog(DEBUG1, "finishing incomplete split of %u/%u",
BufferGetBlockNumber(lbuf), BufferGetBlockNumber(rbuf));
_bt_insert_parent(rel, heaprel, lbuf, rbuf, stack, wasroot, wasonly);
}
/*
* _bt_getstackbuf() -- Walk back up the tree one step, and find the pivot
* tuple whose downlink points to child page.
*
* Caller passes child's block number, which is used to identify
* associated pivot tuple in parent page using a linear search that
* matches on pivot's downlink/block number. The expected location of
* the pivot tuple is taken from the stack one level above the child
* page. This is used as a starting point. Insertions into the
* parent level could cause the pivot tuple to move right; deletions
* could cause it to move left, but not left of the page we previously
* found it on.
*
* Caller can use its stack to relocate the pivot tuple/downlink for
* any same-level page to the right of the page found by its initial
* descent. This is necessary because of the possibility that caller
* moved right to recover from a concurrent page split. It's also
* convenient for certain callers to be able to step right when there
* wasn't a concurrent page split, while still using their original
* stack. For example, the checkingunique _bt_doinsert() case may
* have to step right when there are many physical duplicates, and its
* scantid forces an insertion to the right of the "first page the
* value could be on". (This is also relied on by all of our callers
* when dealing with !heapkeyspace indexes.)
*
* Returns write-locked parent page buffer, or InvalidBuffer if pivot
* tuple not found (should not happen). Adjusts bts_blkno &
* bts_offset if changed. Page split caller should insert its new
* pivot tuple for its new right sibling page on parent page, at the
* offset number bts_offset + 1.
*/
Buffer
_bt_getstackbuf(Relation rel, Relation heaprel, BTStack stack, BlockNumber child)
{
BlockNumber blkno;
OffsetNumber start;
blkno = stack->bts_blkno;
start = stack->bts_offset;
for (;;)
{
Buffer buf;
Page page;
BTPageOpaque opaque;
buf = _bt_getbuf(rel, blkno, BT_WRITE);
page = BufferGetPage(buf);
opaque = BTPageGetOpaque(page);
Assert(heaprel != NULL);
if (P_INCOMPLETE_SPLIT(opaque))
{
_bt_finish_split(rel, heaprel, buf, stack->bts_parent);
continue;
}
if (!P_IGNORE(opaque))
{
OffsetNumber offnum,
minoff,
maxoff;
ItemId itemid;
IndexTuple item;
minoff = P_FIRSTDATAKEY(opaque);
maxoff = PageGetMaxOffsetNumber(page);
/*
* start = InvalidOffsetNumber means "search the whole page". We
* need this test anyway due to possibility that page has a high
* key now when it didn't before.
*/
if (start < minoff)
start = minoff;
/*
* Need this check too, to guard against possibility that page
* split since we visited it originally.
*/
if (start > maxoff)
start = OffsetNumberNext(maxoff);
/*
* These loops will check every item on the page --- but in an
* order that's attuned to the probability of where it actually
* is. Scan to the right first, then to the left.
*/
for (offnum = start;
offnum <= maxoff;
offnum = OffsetNumberNext(offnum))
{
itemid = PageGetItemId(page, offnum);
item = (IndexTuple) PageGetItem(page, itemid);
if (BTreeTupleGetDownLink(item) == child)
{
/* Return accurate pointer to where link is now */
stack->bts_blkno = blkno;
stack->bts_offset = offnum;
return buf;
}
}
for (offnum = OffsetNumberPrev(start);
offnum >= minoff;
offnum = OffsetNumberPrev(offnum))
{
itemid = PageGetItemId(page, offnum);
item = (IndexTuple) PageGetItem(page, itemid);
if (BTreeTupleGetDownLink(item) == child)
{
/* Return accurate pointer to where link is now */
stack->bts_blkno = blkno;
stack->bts_offset = offnum;
return buf;
}
}
}
/*
* The item we're looking for moved right at least one page.
*
* Lehman and Yao couple/chain locks when moving right here, which we
* can avoid. See nbtree/README.
*/
if (P_RIGHTMOST(opaque))
{
_bt_relbuf(rel, buf);
return InvalidBuffer;
}
blkno = opaque->btpo_next;
start = InvalidOffsetNumber;
_bt_relbuf(rel, buf);
}
}
/*
* _bt_newlevel() -- Create a new level above root page.
*
* We've just split the old root page and need to create a new one.
* In order to do this, we add a new root page to the file, then lock
* the metadata page and update it. This is guaranteed to be deadlock-
* free, because all readers release their locks on the metadata page
* before trying to lock the root, and all writers lock the root before
* trying to lock the metadata page. We have a write lock on the old
* root page, so we have not introduced any cycles into the waits-for
* graph.
*
* On entry, lbuf (the old root) and rbuf (its new peer) are write-
* locked. On exit, a new root page exists with entries for the
* two new children, metapage is updated and unlocked/unpinned.
* The new root buffer is returned to caller which has to unlock/unpin
* lbuf, rbuf & rootbuf.
*/
static Buffer
_bt_newlevel(Relation rel, Relation heaprel, Buffer lbuf, Buffer rbuf)
{
Buffer rootbuf;
Page lpage,
rootpage;
BlockNumber lbkno,
rbkno;
BlockNumber rootblknum;
BTPageOpaque rootopaque;
BTPageOpaque lopaque;
ItemId itemid;
IndexTuple item;
IndexTuple left_item;
Size left_item_sz;
IndexTuple right_item;
Size right_item_sz;
Buffer metabuf;
Page metapg;
BTMetaPageData *metad;
lbkno = BufferGetBlockNumber(lbuf);
rbkno = BufferGetBlockNumber(rbuf);
lpage = BufferGetPage(lbuf);
lopaque = BTPageGetOpaque(lpage);
/* get a new root page */
rootbuf = _bt_allocbuf(rel, heaprel);
rootpage = BufferGetPage(rootbuf);
rootblknum = BufferGetBlockNumber(rootbuf);
/* acquire lock on the metapage */
metabuf = _bt_getbuf(rel, BTREE_METAPAGE, BT_WRITE);
metapg = BufferGetPage(metabuf);
metad = BTPageGetMeta(metapg);
/*
* Create downlink item for left page (old root). The key value used is
* "minus infinity", a sentinel value that's reliably less than any real
* key value that could appear in the left page.
*/
left_item_sz = sizeof(IndexTupleData);
left_item = (IndexTuple) palloc(left_item_sz);
left_item->t_info = left_item_sz;
BTreeTupleSetDownLink(left_item, lbkno);
BTreeTupleSetNAtts(left_item, 0, false);
/*
* Create downlink item for right page. The key for it is obtained from
* the "high key" position in the left page.
*/
itemid = PageGetItemId(lpage, P_HIKEY);
right_item_sz = ItemIdGetLength(itemid);
item = (IndexTuple) PageGetItem(lpage, itemid);
right_item = CopyIndexTuple(item);
BTreeTupleSetDownLink(right_item, rbkno);
/* NO EREPORT(ERROR) from here till newroot op is logged */
START_CRIT_SECTION();
/* upgrade metapage if needed */
if (metad->btm_version < BTREE_NOVAC_VERSION)
_bt_upgrademetapage(metapg);
/* set btree special data */
rootopaque = BTPageGetOpaque(rootpage);
rootopaque->btpo_prev = rootopaque->btpo_next = P_NONE;
rootopaque->btpo_flags = BTP_ROOT;
rootopaque->btpo_level =
(BTPageGetOpaque(lpage))->btpo_level + 1;
rootopaque->btpo_cycleid = 0;
/* update metapage data */
metad->btm_root = rootblknum;
metad->btm_level = rootopaque->btpo_level;
metad->btm_fastroot = rootblknum;
metad->btm_fastlevel = rootopaque->btpo_level;
/*
* Insert the left page pointer into the new root page. The root page is
* the rightmost page on its level so there is no "high key" in it; the
* two items will go into positions P_HIKEY and P_FIRSTKEY.
*
* Note: we *must* insert the two items in item-number order, for the
* benefit of _bt_restore_page().
*/
Assert(BTreeTupleGetNAtts(left_item, rel) == 0);
if (PageAddItem(rootpage, (Item) left_item, left_item_sz, P_HIKEY,
false, false) == InvalidOffsetNumber)
elog(PANIC, "failed to add leftkey to new root page"
" while splitting block %u of index \"%s\"",
BufferGetBlockNumber(lbuf), RelationGetRelationName(rel));
/*
* insert the right page pointer into the new root page.
*/
Assert(BTreeTupleGetNAtts(right_item, rel) > 0);
Assert(BTreeTupleGetNAtts(right_item, rel) <=
IndexRelationGetNumberOfKeyAttributes(rel));
if (PageAddItem(rootpage, (Item) right_item, right_item_sz, P_FIRSTKEY,
false, false) == InvalidOffsetNumber)
elog(PANIC, "failed to add rightkey to new root page"
" while splitting block %u of index \"%s\"",
BufferGetBlockNumber(lbuf), RelationGetRelationName(rel));
/* Clear the incomplete-split flag in the left child */
Assert(P_INCOMPLETE_SPLIT(lopaque));
lopaque->btpo_flags &= ~BTP_INCOMPLETE_SPLIT;
MarkBufferDirty(lbuf);
MarkBufferDirty(rootbuf);
MarkBufferDirty(metabuf);
/* XLOG stuff */
if (RelationNeedsWAL(rel))
{
xl_btree_newroot xlrec;
XLogRecPtr recptr;
xl_btree_metadata md;
xlrec.rootblk = rootblknum;
xlrec.level = metad->btm_level;
XLogBeginInsert();
XLogRegisterData((char *) &xlrec, SizeOfBtreeNewroot);
XLogRegisterBuffer(0, rootbuf, REGBUF_WILL_INIT);
XLogRegisterBuffer(1, lbuf, REGBUF_STANDARD);
XLogRegisterBuffer(2, metabuf, REGBUF_WILL_INIT | REGBUF_STANDARD);
Assert(metad->btm_version >= BTREE_NOVAC_VERSION);
md.version = metad->btm_version;
md.root = rootblknum;
md.level = metad->btm_level;
md.fastroot = rootblknum;
md.fastlevel = metad->btm_level;
md.last_cleanup_num_delpages = metad->btm_last_cleanup_num_delpages;
md.allequalimage = metad->btm_allequalimage;
XLogRegisterBufData(2, (char *) &md, sizeof(xl_btree_metadata));
/*
* Direct access to page is not good but faster - we should implement
* some new func in page API.
*/
XLogRegisterBufData(0,
(char *) rootpage + ((PageHeader) rootpage)->pd_upper,
((PageHeader) rootpage)->pd_special -
((PageHeader) rootpage)->pd_upper);
recptr = XLogInsert(RM_BTREE_ID, XLOG_BTREE_NEWROOT);
PageSetLSN(lpage, recptr);
PageSetLSN(rootpage, recptr);
PageSetLSN(metapg, recptr);
}
END_CRIT_SECTION();
/* done with metapage */
_bt_relbuf(rel, metabuf);
pfree(left_item);
pfree(right_item);
return rootbuf;
}
/*
* _bt_pgaddtup() -- add a data item to a particular page during split.
*
* The difference between this routine and a bare PageAddItem call is
* that this code can deal with the first data item on an internal btree
* page in passing. This data item (which is called "firstright" within
* _bt_split()) has a key that must be treated as minus infinity after
* the split. Therefore, we truncate away all attributes when caller
* specifies it's the first data item on page (downlink is not changed,
* though). This extra step is only needed for the right page of an
* internal page split. There is no need to do this for the first data
* item on the existing/left page, since that will already have been
* truncated during an earlier page split.
*
* See _bt_split() for a high level explanation of why we truncate here.
* Note that this routine has nothing to do with suffix truncation,
* despite using some of the same infrastructure.
*/
static inline bool
_bt_pgaddtup(Page page,
Size itemsize,
IndexTuple itup,
OffsetNumber itup_off,
bool newfirstdataitem)
{
IndexTupleData trunctuple;
if (newfirstdataitem)
{
trunctuple = *itup;
trunctuple.t_info = sizeof(IndexTupleData);
BTreeTupleSetNAtts(&trunctuple, 0, false);
itup = &trunctuple;
itemsize = sizeof(IndexTupleData);
}
if (unlikely(PageAddItem(page, (Item) itup, itemsize, itup_off, false,
false) == InvalidOffsetNumber))
return false;
return true;
}
/*
* _bt_delete_or_dedup_one_page - Try to avoid a leaf page split.
*
* There are three operations performed here: simple index deletion, bottom-up
* index deletion, and deduplication. If all three operations fail to free
* enough space for the incoming item then caller will go on to split the
* page. We always consider simple deletion first. If that doesn't work out
* we consider alternatives. Callers that only want us to consider simple
* deletion (without any fallback) ask for that using the 'simpleonly'
* argument.
*
* We usually pick only one alternative "complex" operation when simple
* deletion alone won't prevent a page split. The 'checkingunique',
* 'uniquedup', and 'indexUnchanged' arguments are used for that.
*
* Note: We used to only delete LP_DEAD items when the BTP_HAS_GARBAGE page
* level flag was found set. The flag was useful back when there wasn't
* necessarily one single page for a duplicate tuple to go on (before heap TID
* became a part of the key space in version 4 indexes). But we don't
* actually look at the flag anymore (it's not a gating condition for our
* caller). That would cause us to miss tuples that are safe to delete,
* without getting any benefit in return. We know that the alternative is to
* split the page; scanning the line pointer array in passing won't have
* noticeable overhead. (We still maintain the BTP_HAS_GARBAGE flag despite
* all this because !heapkeyspace indexes must still do a "getting tired"
* linear search, and so are likely to get some benefit from using it as a
* gating condition.)
*/
static void
_bt_delete_or_dedup_one_page(Relation rel, Relation heapRel,
BTInsertState insertstate,
bool simpleonly, bool checkingunique,
bool uniquedup, bool indexUnchanged)
{
OffsetNumber deletable[MaxIndexTuplesPerPage];
int ndeletable = 0;
OffsetNumber offnum,
minoff,
maxoff;
Buffer buffer = insertstate->buf;
BTScanInsert itup_key = insertstate->itup_key;
Page page = BufferGetPage(buffer);
BTPageOpaque opaque = BTPageGetOpaque(page);
Assert(P_ISLEAF(opaque));
Assert(simpleonly || itup_key->heapkeyspace);
Assert(!simpleonly || (!checkingunique && !uniquedup && !indexUnchanged));
/*
* Scan over all items to see which ones need to be deleted according to
* LP_DEAD flags. We'll usually manage to delete a few extra items that
* are not marked LP_DEAD in passing. Often the extra items that actually
* end up getting deleted are items that would have had their LP_DEAD bit
* set before long anyway (if we opted not to include them as extras).
*/
minoff = P_FIRSTDATAKEY(opaque);
maxoff = PageGetMaxOffsetNumber(page);
for (offnum = minoff;
offnum <= maxoff;
offnum = OffsetNumberNext(offnum))
{
ItemId itemId = PageGetItemId(page, offnum);
if (ItemIdIsDead(itemId))
deletable[ndeletable++] = offnum;
}
if (ndeletable > 0)
{
_bt_simpledel_pass(rel, buffer, heapRel, deletable, ndeletable,
insertstate->itup, minoff, maxoff);
insertstate->bounds_valid = false;
/* Return when a page split has already been avoided */
if (PageGetFreeSpace(page) >= insertstate->itemsz)
return;
/* Might as well assume duplicates (if checkingunique) */
uniquedup = true;
}
/*
* We're done with simple deletion. Return early with callers that only
* call here so that simple deletion can be considered. This includes
* callers that explicitly ask for this and checkingunique callers that
* probably don't have any version churn duplicates on the page.
*
* Note: The page's BTP_HAS_GARBAGE hint flag may still be set when we
* return at this point (or when we go on the try either or both of our
* other strategies and they also fail). We do not bother expending a
* separate write to clear it, however. Caller will definitely clear it
* when it goes on to split the page (note also that the deduplication
* process will clear the flag in passing, just to keep things tidy).
*/
if (simpleonly || (checkingunique && !uniquedup))
{
Assert(!indexUnchanged);
return;
}
/* Assume bounds about to be invalidated (this is almost certain now) */
insertstate->bounds_valid = false;
/*
* Perform bottom-up index deletion pass when executor hint indicated that
* incoming item is logically unchanged, or for a unique index that is
* known to have physical duplicates for some other reason. (There is a
* large overlap between these two cases for a unique index. It's worth
* having both triggering conditions in order to apply the optimization in
* the event of successive related INSERT and DELETE statements.)
*
* We'll go on to do a deduplication pass when a bottom-up pass fails to
* delete an acceptable amount of free space (a significant fraction of
* the page, or space for the new item, whichever is greater).
*
* Note: Bottom-up index deletion uses the same equality/equivalence
* routines as deduplication internally. However, it does not merge
* together index tuples, so the same correctness considerations do not
* apply. We deliberately omit an index-is-allequalimage test here.
*/
if ((indexUnchanged || uniquedup) &&
_bt_bottomupdel_pass(rel, buffer, heapRel, insertstate->itemsz))
return;
/* Perform deduplication pass (when enabled and index-is-allequalimage) */
if (BTGetDeduplicateItems(rel) && itup_key->allequalimage)
_bt_dedup_pass(rel, buffer, insertstate->itup, insertstate->itemsz,
(indexUnchanged || uniquedup));
}
/*
* _bt_simpledel_pass - Simple index tuple deletion pass.
*
* We delete all LP_DEAD-set index tuples on a leaf page. The offset numbers
* of all such tuples are determined by caller (caller passes these to us as
* its 'deletable' argument).
*
* We might also delete extra index tuples that turn out to be safe to delete
* in passing (though they must be cheap to check in passing to begin with).
* There is no certainty that any extra tuples will be deleted, though. The
* high level goal of the approach we take is to get the most out of each call
* here (without noticeably increasing the per-call overhead compared to what
* we need to do just to be able to delete the page's LP_DEAD-marked index
* tuples).
*
* The number of extra index tuples that turn out to be deletable might
* greatly exceed the number of LP_DEAD-marked index tuples due to various
* locality related effects. For example, it's possible that the total number
* of table blocks (pointed to by all TIDs on the leaf page) is naturally
* quite low, in which case we might end up checking if it's possible to
* delete _most_ index tuples on the page (without the tableam needing to
* access additional table blocks). The tableam will sometimes stumble upon
* _many_ extra deletable index tuples in indexes where this pattern is
* common.
*
* See nbtree/README for further details on simple index tuple deletion.
*/
static void
_bt_simpledel_pass(Relation rel, Buffer buffer, Relation heapRel,
OffsetNumber *deletable, int ndeletable, IndexTuple newitem,
OffsetNumber minoff, OffsetNumber maxoff)
{
Page page = BufferGetPage(buffer);
BlockNumber *deadblocks;
int ndeadblocks;
TM_IndexDeleteOp delstate;
OffsetNumber offnum;
/* Get array of table blocks pointed to by LP_DEAD-set tuples */
deadblocks = _bt_deadblocks(page, deletable, ndeletable, newitem,
&ndeadblocks);
/* Initialize tableam state that describes index deletion operation */
delstate.irel = rel;
delstate.iblknum = BufferGetBlockNumber(buffer);
delstate.bottomup = false;
delstate.bottomupfreespace = 0;
delstate.ndeltids = 0;
delstate.deltids = palloc(MaxTIDsPerBTreePage * sizeof(TM_IndexDelete));
delstate.status = palloc(MaxTIDsPerBTreePage * sizeof(TM_IndexStatus));
for (offnum = minoff;
offnum <= maxoff;
offnum = OffsetNumberNext(offnum))
{
ItemId itemid = PageGetItemId(page, offnum);
IndexTuple itup = (IndexTuple) PageGetItem(page, itemid);
TM_IndexDelete *odeltid = &delstate.deltids[delstate.ndeltids];
TM_IndexStatus *ostatus = &delstate.status[delstate.ndeltids];
BlockNumber tidblock;
void *match;
if (!BTreeTupleIsPosting(itup))
{
tidblock = ItemPointerGetBlockNumber(&itup->t_tid);
match = bsearch(&tidblock, deadblocks, ndeadblocks,
sizeof(BlockNumber), _bt_blk_cmp);
if (!match)
{
Assert(!ItemIdIsDead(itemid));
continue;
}
/*
* TID's table block is among those pointed to by the TIDs from
* LP_DEAD-bit set tuples on page -- add TID to deltids
*/
odeltid->tid = itup->t_tid;
odeltid->id = delstate.ndeltids;
ostatus->idxoffnum = offnum;
ostatus->knowndeletable = ItemIdIsDead(itemid);
ostatus->promising = false; /* unused */
ostatus->freespace = 0; /* unused */
delstate.ndeltids++;
}
else
{
int nitem = BTreeTupleGetNPosting(itup);
for (int p = 0; p < nitem; p++)
{
ItemPointer tid = BTreeTupleGetPostingN(itup, p);
tidblock = ItemPointerGetBlockNumber(tid);
match = bsearch(&tidblock, deadblocks, ndeadblocks,
sizeof(BlockNumber), _bt_blk_cmp);
if (!match)
{
Assert(!ItemIdIsDead(itemid));
continue;
}
/*
* TID's table block is among those pointed to by the TIDs
* from LP_DEAD-bit set tuples on page -- add TID to deltids
*/
odeltid->tid = *tid;
odeltid->id = delstate.ndeltids;
ostatus->idxoffnum = offnum;
ostatus->knowndeletable = ItemIdIsDead(itemid);
ostatus->promising = false; /* unused */
ostatus->freespace = 0; /* unused */
odeltid++;
ostatus++;
delstate.ndeltids++;
}
}
}
pfree(deadblocks);
Assert(delstate.ndeltids >= ndeletable);
/* Physically delete LP_DEAD tuples (plus any delete-safe extra TIDs) */
_bt_delitems_delete_check(rel, buffer, heapRel, &delstate);
pfree(delstate.deltids);
pfree(delstate.status);
}
/*
* _bt_deadblocks() -- Get LP_DEAD related table blocks.
*
* Builds sorted and unique-ified array of table block numbers from index
* tuple TIDs whose line pointers are marked LP_DEAD. Also adds the table
* block from incoming newitem just in case it isn't among the LP_DEAD-related
* table blocks.
*
* Always counting the newitem's table block as an LP_DEAD related block makes
* sense because the cost is consistently low; it is practically certain that
* the table block will not incur a buffer miss in tableam. On the other hand
* the benefit is often quite high. There is a decent chance that there will
* be some deletable items from this block, since in general most garbage
* tuples became garbage in the recent past (in many cases this won't be the
* first logical row that core code added to/modified in table block
* recently).
*
* Returns final array, and sets *nblocks to its final size for caller.
*/
static BlockNumber *
_bt_deadblocks(Page page, OffsetNumber *deletable, int ndeletable,
IndexTuple newitem, int *nblocks)
{
int spacentids,
ntids;
BlockNumber *tidblocks;
/*
* Accumulate each TID's block in array whose initial size has space for
* one table block per LP_DEAD-set tuple (plus space for the newitem table
* block). Array will only need to grow when there are LP_DEAD-marked
* posting list tuples (which is not that common).
*/
spacentids = ndeletable + 1;
ntids = 0;
tidblocks = (BlockNumber *) palloc(sizeof(BlockNumber) * spacentids);
/*
* First add the table block for the incoming newitem. This is the one
* case where simple deletion can visit a table block that doesn't have
* any known deletable items.
*/
Assert(!BTreeTupleIsPosting(newitem) && !BTreeTupleIsPivot(newitem));
tidblocks[ntids++] = ItemPointerGetBlockNumber(&newitem->t_tid);
for (int i = 0; i < ndeletable; i++)
{
ItemId itemid = PageGetItemId(page, deletable[i]);
IndexTuple itup = (IndexTuple) PageGetItem(page, itemid);
Assert(ItemIdIsDead(itemid));
if (!BTreeTupleIsPosting(itup))
{
if (ntids + 1 > spacentids)
{
spacentids *= 2;
tidblocks = (BlockNumber *)
repalloc(tidblocks, sizeof(BlockNumber) * spacentids);
}
tidblocks[ntids++] = ItemPointerGetBlockNumber(&itup->t_tid);
}
else
{
int nposting = BTreeTupleGetNPosting(itup);
if (ntids + nposting > spacentids)
{
spacentids = Max(spacentids * 2, ntids + nposting);
tidblocks = (BlockNumber *)
repalloc(tidblocks, sizeof(BlockNumber) * spacentids);
}
for (int j = 0; j < nposting; j++)
{
ItemPointer tid = BTreeTupleGetPostingN(itup, j);
tidblocks[ntids++] = ItemPointerGetBlockNumber(tid);
}
}
}
qsort(tidblocks, ntids, sizeof(BlockNumber), _bt_blk_cmp);
*nblocks = qunique(tidblocks, ntids, sizeof(BlockNumber), _bt_blk_cmp);
return tidblocks;
}
/*
* _bt_blk_cmp() -- qsort comparison function for _bt_simpledel_pass
*/
static inline int
_bt_blk_cmp(const void *arg1, const void *arg2)
{
BlockNumber b1 = *((BlockNumber *) arg1);
BlockNumber b2 = *((BlockNumber *) arg2);
return pg_cmp_u32(b1, b2);
}
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