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1351 lines
42 KiB
C
1351 lines
42 KiB
C
/*-------------------------------------------------------------------------
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*
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* btinsert.c
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* Item insertion in Lehman and Yao btrees for Postgres.
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*
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* Portions Copyright (c) 1996-2000, PostgreSQL, Inc
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtinsert.c,v 1.70 2000/12/03 10:27:26 vadim Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "access/heapam.h"
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#include "access/nbtree.h"
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typedef struct
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{
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/* context data for _bt_checksplitloc */
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Size newitemsz; /* size of new item to be inserted */
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bool non_leaf; /* T if splitting an internal node */
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bool have_split; /* found a valid split? */
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/* these fields valid only if have_split is true */
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bool newitemonleft; /* new item on left or right of best split */
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OffsetNumber firstright; /* best split point */
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int best_delta; /* best size delta so far */
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} FindSplitData;
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void _bt_newroot(Relation rel, Buffer lbuf, Buffer rbuf);
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static TransactionId _bt_check_unique(Relation rel, BTItem btitem,
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Relation heapRel, Buffer buf,
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ScanKey itup_scankey);
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static InsertIndexResult _bt_insertonpg(Relation rel, Buffer buf,
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BTStack stack,
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int keysz, ScanKey scankey,
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BTItem btitem,
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OffsetNumber afteritem);
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static Buffer _bt_split(Relation rel, Buffer buf, OffsetNumber firstright,
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OffsetNumber newitemoff, Size newitemsz,
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BTItem newitem, bool newitemonleft,
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OffsetNumber *itup_off, BlockNumber *itup_blkno);
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static OffsetNumber _bt_findsplitloc(Relation rel, Page page,
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OffsetNumber newitemoff,
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Size newitemsz,
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bool *newitemonleft);
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static void _bt_checksplitloc(FindSplitData *state, OffsetNumber firstright,
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int leftfree, int rightfree,
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bool newitemonleft, Size firstrightitemsz);
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static Buffer _bt_getstackbuf(Relation rel, BTStack stack);
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static void _bt_pgaddtup(Relation rel, Page page,
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Size itemsize, BTItem btitem,
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OffsetNumber itup_off, const char *where);
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static bool _bt_isequal(TupleDesc itupdesc, Page page, OffsetNumber offnum,
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int keysz, ScanKey scankey);
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static Relation _xlheapRel; /* temporary hack */
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/*
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* _bt_doinsert() -- Handle insertion of a single btitem in the tree.
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*
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* This routine is called by the public interface routines, btbuild
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* and btinsert. By here, btitem is filled in, including the TID.
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*/
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InsertIndexResult
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_bt_doinsert(Relation rel, BTItem btitem,
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bool index_is_unique, Relation heapRel)
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{
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IndexTuple itup = &(btitem->bti_itup);
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int natts = rel->rd_rel->relnatts;
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ScanKey itup_scankey;
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BTStack stack;
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Buffer buf;
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InsertIndexResult res;
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/* we need a scan key to do our search, so build one */
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itup_scankey = _bt_mkscankey(rel, itup);
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top:
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/* find the page containing this key */
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stack = _bt_search(rel, natts, itup_scankey, &buf, BT_WRITE);
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/* trade in our read lock for a write lock */
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LockBuffer(buf, BUFFER_LOCK_UNLOCK);
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LockBuffer(buf, BT_WRITE);
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/*
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* If the page was split between the time that we surrendered our read
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* lock and acquired our write lock, then this page may no longer be
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* the right place for the key we want to insert. In this case, we
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* need to move right in the tree. See Lehman and Yao for an
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* excruciatingly precise description.
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*/
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buf = _bt_moveright(rel, buf, natts, itup_scankey, BT_WRITE);
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/*
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* If we're not allowing duplicates, make sure the key isn't
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* already in the index. XXX this belongs somewhere else, likely
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*/
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if (index_is_unique)
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{
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TransactionId xwait;
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xwait = _bt_check_unique(rel, btitem, heapRel, buf, itup_scankey);
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if (TransactionIdIsValid(xwait))
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{
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/* Have to wait for the other guy ... */
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_bt_relbuf(rel, buf, BT_WRITE);
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XactLockTableWait(xwait);
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/* start over... */
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_bt_freestack(stack);
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goto top;
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}
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}
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_xlheapRel = heapRel; /* temporary hack */
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/* do the insertion */
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res = _bt_insertonpg(rel, buf, stack, natts, itup_scankey, btitem, 0);
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/* be tidy */
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_bt_freestack(stack);
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_bt_freeskey(itup_scankey);
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return res;
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}
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/*
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* _bt_check_unique() -- Check for violation of unique index constraint
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*
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* Returns NullTransactionId if there is no conflict, else an xact ID we
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* must wait for to see if it commits a conflicting tuple. If an actual
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* conflict is detected, no return --- just elog().
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*/
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static TransactionId
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_bt_check_unique(Relation rel, BTItem btitem, Relation heapRel,
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Buffer buf, ScanKey itup_scankey)
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{
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TupleDesc itupdesc = RelationGetDescr(rel);
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int natts = rel->rd_rel->relnatts;
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OffsetNumber offset,
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maxoff;
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Page page;
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BTPageOpaque opaque;
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Buffer nbuf = InvalidBuffer;
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bool chtup = true;
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page = BufferGetPage(buf);
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opaque = (BTPageOpaque) PageGetSpecialPointer(page);
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maxoff = PageGetMaxOffsetNumber(page);
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/*
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* Find first item >= proposed new item. Note we could also get
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* a pointer to end-of-page here.
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*/
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offset = _bt_binsrch(rel, buf, natts, itup_scankey);
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/*
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* Scan over all equal tuples, looking for live conflicts.
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*/
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for (;;)
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{
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HeapTupleData htup;
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Buffer buffer;
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BTItem cbti;
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BlockNumber nblkno;
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/*
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* _bt_compare returns 0 for (1,NULL) and (1,NULL) - this's
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* how we handling NULLs - and so we must not use _bt_compare
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* in real comparison, but only for ordering/finding items on
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* pages. - vadim 03/24/97
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*
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* make sure the offset points to an actual key
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* before trying to compare it...
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*/
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if (offset <= maxoff)
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{
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if (! _bt_isequal(itupdesc, page, offset, natts, itup_scankey))
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break; /* we're past all the equal tuples */
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/*
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* Have to check is inserted heap tuple deleted one (i.e.
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* just moved to another place by vacuum)! We only need to
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* do this once, but don't want to do it at all unless
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* we see equal tuples, so as not to slow down unequal case.
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*/
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if (chtup)
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{
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htup.t_self = btitem->bti_itup.t_tid;
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heap_fetch(heapRel, SnapshotDirty, &htup, &buffer);
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if (htup.t_data == NULL) /* YES! */
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break;
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/* Live tuple is being inserted, so continue checking */
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ReleaseBuffer(buffer);
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chtup = false;
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}
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cbti = (BTItem) PageGetItem(page, PageGetItemId(page, offset));
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htup.t_self = cbti->bti_itup.t_tid;
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heap_fetch(heapRel, SnapshotDirty, &htup, &buffer);
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if (htup.t_data != NULL) /* it is a duplicate */
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{
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TransactionId xwait =
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(TransactionIdIsValid(SnapshotDirty->xmin)) ?
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SnapshotDirty->xmin : SnapshotDirty->xmax;
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/*
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* If this tuple is being updated by other transaction
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* then we have to wait for its commit/abort.
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*/
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ReleaseBuffer(buffer);
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if (TransactionIdIsValid(xwait))
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{
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if (nbuf != InvalidBuffer)
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_bt_relbuf(rel, nbuf, BT_READ);
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/* Tell _bt_doinsert to wait... */
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return xwait;
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}
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/*
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* Otherwise we have a definite conflict.
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*/
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elog(ERROR, "Cannot insert a duplicate key into unique index %s",
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RelationGetRelationName(rel));
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}
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/* htup null so no buffer to release */
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}
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/*
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* Advance to next tuple to continue checking.
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*/
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if (offset < maxoff)
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offset = OffsetNumberNext(offset);
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else
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{
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/* If scankey == hikey we gotta check the next page too */
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if (P_RIGHTMOST(opaque))
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break;
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if (!_bt_isequal(itupdesc, page, P_HIKEY,
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natts, itup_scankey))
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break;
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nblkno = opaque->btpo_next;
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if (nbuf != InvalidBuffer)
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_bt_relbuf(rel, nbuf, BT_READ);
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nbuf = _bt_getbuf(rel, nblkno, BT_READ);
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page = BufferGetPage(nbuf);
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opaque = (BTPageOpaque) PageGetSpecialPointer(page);
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maxoff = PageGetMaxOffsetNumber(page);
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offset = P_FIRSTDATAKEY(opaque);
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}
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}
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if (nbuf != InvalidBuffer)
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_bt_relbuf(rel, nbuf, BT_READ);
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return NullTransactionId;
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}
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/*----------
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* _bt_insertonpg() -- Insert a tuple on a particular page in the index.
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*
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* This recursive procedure does the following things:
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*
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* + finds the right place to insert the tuple.
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* + if necessary, splits the target page (making sure that the
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* split is equitable as far as post-insert free space goes).
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* + inserts the tuple.
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* + if the page was split, pops the parent stack, and finds the
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* right place to insert the new child pointer (by walking
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* right using information stored in the parent stack).
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* + invokes itself with the appropriate tuple for the right
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* child page on the parent.
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*
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* On entry, we must have the right buffer on which to do the
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* insertion, and the buffer must be pinned and locked. On return,
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* we will have dropped both the pin and the write lock on the buffer.
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*
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* If 'afteritem' is >0 then the new tuple must be inserted after the
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* existing item of that number, noplace else. If 'afteritem' is 0
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* then the procedure finds the exact spot to insert it by searching.
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* (keysz and scankey parameters are used ONLY if afteritem == 0.)
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*
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* NOTE: if the new key is equal to one or more existing keys, we can
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* legitimately place it anywhere in the series of equal keys --- in fact,
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* if the new key is equal to the page's "high key" we can place it on
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* the next page. If it is equal to the high key, and there's not room
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* to insert the new tuple on the current page without splitting, then
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* we can move right hoping to find more free space and avoid a split.
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* (We should not move right indefinitely, however, since that leads to
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* O(N^2) insertion behavior in the presence of many equal keys.)
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* Once we have chosen the page to put the key on, we'll insert it before
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* any existing equal keys because of the way _bt_binsrch() works.
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*
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* The locking interactions in this code are critical. You should
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* grok Lehman and Yao's paper before making any changes. In addition,
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* you need to understand how we disambiguate duplicate keys in this
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* implementation, in order to be able to find our location using
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* L&Y "move right" operations. Since we may insert duplicate user
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* keys, and since these dups may propagate up the tree, we use the
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* 'afteritem' parameter to position ourselves correctly for the
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* insertion on internal pages.
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*----------
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*/
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static InsertIndexResult
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_bt_insertonpg(Relation rel,
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Buffer buf,
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BTStack stack,
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int keysz,
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ScanKey scankey,
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BTItem btitem,
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OffsetNumber afteritem)
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{
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InsertIndexResult res;
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Page page;
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BTPageOpaque lpageop;
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OffsetNumber itup_off;
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BlockNumber itup_blkno;
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OffsetNumber newitemoff;
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OffsetNumber firstright = InvalidOffsetNumber;
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Size itemsz;
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page = BufferGetPage(buf);
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lpageop = (BTPageOpaque) PageGetSpecialPointer(page);
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itemsz = IndexTupleDSize(btitem->bti_itup)
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+ (sizeof(BTItemData) - sizeof(IndexTupleData));
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itemsz = MAXALIGN(itemsz); /* be safe, PageAddItem will do this but
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* we need to be consistent */
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/*
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* Check whether the item can fit on a btree page at all. (Eventually,
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* we ought to try to apply TOAST methods if not.) We actually need to
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* be able to fit three items on every page, so restrict any one item
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* to 1/3 the per-page available space. Note that at this point,
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* itemsz doesn't include the ItemId.
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*/
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if (itemsz > (PageGetPageSize(page) - sizeof(PageHeaderData) - MAXALIGN(sizeof(BTPageOpaqueData))) / 3 - sizeof(ItemIdData))
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elog(ERROR, "btree: index item size %lu exceeds maximum %lu",
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(unsigned long)itemsz,
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(PageGetPageSize(page) - sizeof(PageHeaderData) - MAXALIGN(sizeof(BTPageOpaqueData))) /3 - sizeof(ItemIdData));
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/*
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* Determine exactly where new item will go.
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*/
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if (afteritem > 0)
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{
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newitemoff = afteritem + 1;
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}
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else
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{
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/*----------
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* If we will need to split the page to put the item here,
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* check whether we can put the tuple somewhere to the right,
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* instead. Keep scanning right until we
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* (a) find a page with enough free space,
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* (b) reach the last page where the tuple can legally go, or
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* (c) get tired of searching.
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* (c) is not flippant; it is important because if there are many
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* pages' worth of equal keys, it's better to split one of the early
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* pages than to scan all the way to the end of the run of equal keys
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* on every insert. We implement "get tired" as a random choice,
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* since stopping after scanning a fixed number of pages wouldn't work
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* well (we'd never reach the right-hand side of previously split
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* pages). Currently the probability of moving right is set at 0.99,
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* which may seem too high to change the behavior much, but it does an
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* excellent job of preventing O(N^2) behavior with many equal keys.
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*----------
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*/
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bool movedright = false;
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while (PageGetFreeSpace(page) < itemsz &&
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!P_RIGHTMOST(lpageop) &&
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_bt_compare(rel, keysz, scankey, page, P_HIKEY) == 0 &&
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random() > (MAX_RANDOM_VALUE / 100))
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{
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/* step right one page */
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BlockNumber rblkno = lpageop->btpo_next;
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_bt_relbuf(rel, buf, BT_WRITE);
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buf = _bt_getbuf(rel, rblkno, BT_WRITE);
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page = BufferGetPage(buf);
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lpageop = (BTPageOpaque) PageGetSpecialPointer(page);
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movedright = true;
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}
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/*
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* Now we are on the right page, so find the insert position.
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* If we moved right at all, we know we should insert at the
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* start of the page, else must find the position by searching.
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*/
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if (movedright)
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newitemoff = P_FIRSTDATAKEY(lpageop);
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else
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newitemoff = _bt_binsrch(rel, buf, keysz, scankey);
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}
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/*
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* Do we need to split the page to fit the item on it?
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*
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* Note: PageGetFreeSpace() subtracts sizeof(ItemIdData) from its
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* result, so this comparison is correct even though we appear to
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* be accounting only for the item and not for its line pointer.
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*/
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if (PageGetFreeSpace(page) < itemsz)
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{
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Buffer rbuf;
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BlockNumber bknum = BufferGetBlockNumber(buf);
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BlockNumber rbknum;
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bool is_root = P_ISROOT(lpageop);
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bool newitemonleft;
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/* Choose the split point */
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firstright = _bt_findsplitloc(rel, page,
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newitemoff, itemsz,
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&newitemonleft);
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/* split the buffer into left and right halves */
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rbuf = _bt_split(rel, buf, firstright,
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newitemoff, itemsz, btitem, newitemonleft,
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&itup_off, &itup_blkno);
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/*----------
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* By here,
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*
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* + our target page has been split;
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* + the original tuple has been inserted;
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* + we have write locks on both the old (left half)
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* and new (right half) buffers, after the split; and
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* + we know the key we want to insert into the parent
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* (it's the "high key" on the left child page).
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*
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* We're ready to do the parent insertion. We need to hold onto the
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* locks for the child pages until we locate the parent, but we can
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* release them before doing the actual insertion (see Lehman and Yao
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* for the reasoning).
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*
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* Here we have to do something Lehman and Yao don't talk about:
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* deal with a root split and construction of a new root. If our
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* stack is empty then we have just split a node on what had been
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* the root level when we descended the tree. If it is still the
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* root then we perform a new-root construction. If it *wasn't*
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* the root anymore, use the parent pointer to get up to the root
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* level that someone constructed meanwhile, and find the right
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* place to insert as for the normal case.
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*----------
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*/
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if (is_root)
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{
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Assert(stack == (BTStack) NULL);
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/* create a new root node and release the split buffers */
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_bt_newroot(rel, buf, rbuf);
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}
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else
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{
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InsertIndexResult newres;
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BTItem new_item;
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BTStackData fakestack;
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BTItem ritem;
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Buffer pbuf;
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/* Set up a phony stack entry if we haven't got a real one */
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if (stack == (BTStack) NULL)
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{
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elog(DEBUG, "btree: concurrent ROOT page split");
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stack = &fakestack;
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stack->bts_blkno = lpageop->btpo_parent;
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stack->bts_offset = InvalidOffsetNumber;
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/* bts_btitem will be initialized below */
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stack->bts_parent = NULL;
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}
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/* get high key from left page == lowest key on new right page */
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ritem = (BTItem) PageGetItem(page,
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PageGetItemId(page, P_HIKEY));
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/* form an index tuple that points at the new right page */
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new_item = _bt_formitem(&(ritem->bti_itup));
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rbknum = BufferGetBlockNumber(rbuf);
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ItemPointerSet(&(new_item->bti_itup.t_tid), rbknum, P_HIKEY);
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/*
|
|
* Find the parent buffer and get the parent page.
|
|
*
|
|
* Oops - if we were moved right then we need to change stack
|
|
* item! We want to find parent pointing to where we are,
|
|
* right ? - vadim 05/27/97
|
|
*
|
|
* Interestingly, this means we didn't *really* need to stack
|
|
* the parent key at all; all we really care about is the
|
|
* saved block and offset as a starting point for our search...
|
|
*/
|
|
ItemPointerSet(&(stack->bts_btitem.bti_itup.t_tid),
|
|
bknum, P_HIKEY);
|
|
|
|
pbuf = _bt_getstackbuf(rel, stack);
|
|
|
|
/* Now we can write and unlock the children */
|
|
_bt_wrtbuf(rel, rbuf);
|
|
_bt_wrtbuf(rel, buf);
|
|
|
|
/* Recursively update the parent */
|
|
newres = _bt_insertonpg(rel, pbuf, stack->bts_parent,
|
|
0, NULL, new_item, stack->bts_offset);
|
|
|
|
/* be tidy */
|
|
pfree(newres);
|
|
pfree(new_item);
|
|
}
|
|
}
|
|
else
|
|
{
|
|
/* XLOG stuff */
|
|
{
|
|
char xlbuf[sizeof(xl_btree_insert) +
|
|
sizeof(CommandId) + sizeof(RelFileNode)];
|
|
xl_btree_insert *xlrec = (xl_btree_insert*)xlbuf;
|
|
int hsize = SizeOfBtreeInsert;
|
|
BTItemData truncitem;
|
|
BTItem xlitem = btitem;
|
|
Size xlsize = IndexTupleDSize(btitem->bti_itup) +
|
|
(sizeof(BTItemData) - sizeof(IndexTupleData));
|
|
XLogRecPtr recptr;
|
|
|
|
xlrec->target.node = rel->rd_node;
|
|
ItemPointerSet(&(xlrec->target.tid), BufferGetBlockNumber(buf), newitemoff);
|
|
if (P_ISLEAF(lpageop))
|
|
{
|
|
CommandId cid = GetCurrentCommandId();
|
|
memcpy(xlbuf + hsize, &cid, sizeof(CommandId));
|
|
hsize += sizeof(CommandId);
|
|
memcpy(xlbuf + hsize, &(_xlheapRel->rd_node), sizeof(RelFileNode));
|
|
hsize += sizeof(RelFileNode);
|
|
}
|
|
/*
|
|
* Read comments in _bt_pgaddtup
|
|
*/
|
|
else if (newitemoff == P_FIRSTDATAKEY(lpageop))
|
|
{
|
|
truncitem = *btitem;
|
|
truncitem.bti_itup.t_info = sizeof(BTItemData);
|
|
xlitem = &truncitem;
|
|
xlsize = sizeof(BTItemData);
|
|
}
|
|
|
|
recptr = XLogInsert(RM_BTREE_ID, XLOG_BTREE_INSERT,
|
|
xlbuf, hsize, (char*) xlitem, xlsize);
|
|
|
|
PageSetLSN(page, recptr);
|
|
PageSetSUI(page, ThisStartUpID);
|
|
}
|
|
|
|
_bt_pgaddtup(rel, page, itemsz, btitem, newitemoff, "page");
|
|
itup_off = newitemoff;
|
|
itup_blkno = BufferGetBlockNumber(buf);
|
|
/* Write out the updated page and release pin/lock */
|
|
_bt_wrtbuf(rel, buf);
|
|
}
|
|
|
|
/* by here, the new tuple is inserted at itup_blkno/itup_off */
|
|
res = (InsertIndexResult) palloc(sizeof(InsertIndexResultData));
|
|
ItemPointerSet(&(res->pointerData), itup_blkno, itup_off);
|
|
|
|
return res;
|
|
}
|
|
|
|
/*
|
|
* _bt_split() -- split a page in the btree.
|
|
*
|
|
* On entry, buf is the page to split, and is write-locked and pinned.
|
|
* firstright is the item index of the first item to be moved to the
|
|
* new right page. newitemoff etc. tell us about the new item that
|
|
* must be inserted along with the data from the old page.
|
|
*
|
|
* Returns the new right sibling of buf, pinned and write-locked.
|
|
* The pin and lock on buf are maintained. *itup_off and *itup_blkno
|
|
* are set to the exact location where newitem was inserted.
|
|
*/
|
|
static Buffer
|
|
_bt_split(Relation rel, Buffer buf, OffsetNumber firstright,
|
|
OffsetNumber newitemoff, Size newitemsz, BTItem newitem,
|
|
bool newitemonleft,
|
|
OffsetNumber *itup_off, BlockNumber *itup_blkno)
|
|
{
|
|
Buffer rbuf;
|
|
Page origpage;
|
|
Page leftpage,
|
|
rightpage;
|
|
BTPageOpaque ropaque,
|
|
lopaque,
|
|
oopaque;
|
|
Buffer sbuf = 0;
|
|
Page spage = 0;
|
|
BTPageOpaque sopaque;
|
|
Size itemsz;
|
|
ItemId itemid;
|
|
BTItem item;
|
|
OffsetNumber leftoff,
|
|
rightoff;
|
|
OffsetNumber maxoff;
|
|
OffsetNumber i;
|
|
BTItem lhikey;
|
|
|
|
rbuf = _bt_getbuf(rel, P_NEW, BT_WRITE);
|
|
origpage = BufferGetPage(buf);
|
|
leftpage = PageGetTempPage(origpage, sizeof(BTPageOpaqueData));
|
|
rightpage = BufferGetPage(rbuf);
|
|
|
|
_bt_pageinit(leftpage, BufferGetPageSize(buf));
|
|
_bt_pageinit(rightpage, BufferGetPageSize(rbuf));
|
|
|
|
/* init btree private data */
|
|
oopaque = (BTPageOpaque) PageGetSpecialPointer(origpage);
|
|
lopaque = (BTPageOpaque) PageGetSpecialPointer(leftpage);
|
|
ropaque = (BTPageOpaque) PageGetSpecialPointer(rightpage);
|
|
|
|
/* if we're splitting this page, it won't be the root when we're done */
|
|
lopaque->btpo_flags = oopaque->btpo_flags;
|
|
lopaque->btpo_flags &= ~BTP_ROOT;
|
|
ropaque->btpo_flags = lopaque->btpo_flags;
|
|
lopaque->btpo_prev = oopaque->btpo_prev;
|
|
lopaque->btpo_next = BufferGetBlockNumber(rbuf);
|
|
ropaque->btpo_prev = BufferGetBlockNumber(buf);
|
|
ropaque->btpo_next = oopaque->btpo_next;
|
|
|
|
/*
|
|
* Must copy the original parent link into both new pages, even though
|
|
* it might be quite obsolete by now. We might need it if this level
|
|
* is or recently was the root (see README).
|
|
*/
|
|
lopaque->btpo_parent = ropaque->btpo_parent = oopaque->btpo_parent;
|
|
|
|
/*
|
|
* 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
|
|
* for the page. We need to copy that to the right half. Otherwise
|
|
* (meaning the rightmost page case), all the items on the right half
|
|
* will be user data.
|
|
*/
|
|
rightoff = P_HIKEY;
|
|
|
|
if (!P_RIGHTMOST(oopaque))
|
|
{
|
|
itemid = PageGetItemId(origpage, P_HIKEY);
|
|
itemsz = ItemIdGetLength(itemid);
|
|
item = (BTItem) PageGetItem(origpage, itemid);
|
|
if (PageAddItem(rightpage, (Item) item, itemsz, rightoff,
|
|
LP_USED) == InvalidOffsetNumber)
|
|
elog(STOP, "btree: failed to add hikey to the right sibling");
|
|
rightoff = OffsetNumberNext(rightoff);
|
|
}
|
|
|
|
/*
|
|
* The "high key" for the new left page will be the first key that's
|
|
* going to go into the new right page. This might be either the
|
|
* existing data item at position firstright, or the incoming tuple.
|
|
*/
|
|
leftoff = P_HIKEY;
|
|
if (!newitemonleft && newitemoff == firstright)
|
|
{
|
|
/* incoming tuple will become first on right page */
|
|
itemsz = newitemsz;
|
|
item = newitem;
|
|
}
|
|
else
|
|
{
|
|
/* existing item at firstright will become first on right page */
|
|
itemid = PageGetItemId(origpage, firstright);
|
|
itemsz = ItemIdGetLength(itemid);
|
|
item = (BTItem) PageGetItem(origpage, itemid);
|
|
}
|
|
lhikey = item;
|
|
if (PageAddItem(leftpage, (Item) item, itemsz, leftoff,
|
|
LP_USED) == InvalidOffsetNumber)
|
|
elog(STOP, "btree: failed to add hikey to the left sibling");
|
|
leftoff = OffsetNumberNext(leftoff);
|
|
|
|
/*
|
|
* Now transfer all the data items to the appropriate page
|
|
*/
|
|
maxoff = PageGetMaxOffsetNumber(origpage);
|
|
|
|
for (i = P_FIRSTDATAKEY(oopaque); i <= maxoff; i = OffsetNumberNext(i))
|
|
{
|
|
itemid = PageGetItemId(origpage, i);
|
|
itemsz = ItemIdGetLength(itemid);
|
|
item = (BTItem) PageGetItem(origpage, itemid);
|
|
|
|
/* does new item belong before this one? */
|
|
if (i == newitemoff)
|
|
{
|
|
if (newitemonleft)
|
|
{
|
|
_bt_pgaddtup(rel, leftpage, newitemsz, newitem, leftoff,
|
|
"left sibling");
|
|
*itup_off = leftoff;
|
|
*itup_blkno = BufferGetBlockNumber(buf);
|
|
leftoff = OffsetNumberNext(leftoff);
|
|
}
|
|
else
|
|
{
|
|
_bt_pgaddtup(rel, rightpage, newitemsz, newitem, rightoff,
|
|
"right sibling");
|
|
*itup_off = rightoff;
|
|
*itup_blkno = BufferGetBlockNumber(rbuf);
|
|
rightoff = OffsetNumberNext(rightoff);
|
|
}
|
|
}
|
|
|
|
/* decide which page to put it on */
|
|
if (i < firstright)
|
|
{
|
|
_bt_pgaddtup(rel, leftpage, itemsz, item, leftoff,
|
|
"left sibling");
|
|
leftoff = OffsetNumberNext(leftoff);
|
|
}
|
|
else
|
|
{
|
|
_bt_pgaddtup(rel, rightpage, itemsz, item, rightoff,
|
|
"right sibling");
|
|
rightoff = OffsetNumberNext(rightoff);
|
|
}
|
|
}
|
|
|
|
/* cope with possibility that newitem goes at the end */
|
|
if (i <= newitemoff)
|
|
{
|
|
if (newitemonleft)
|
|
{
|
|
_bt_pgaddtup(rel, leftpage, newitemsz, newitem, leftoff,
|
|
"left sibling");
|
|
*itup_off = leftoff;
|
|
*itup_blkno = BufferGetBlockNumber(buf);
|
|
leftoff = OffsetNumberNext(leftoff);
|
|
}
|
|
else
|
|
{
|
|
_bt_pgaddtup(rel, rightpage, newitemsz, newitem, rightoff,
|
|
"right sibling");
|
|
*itup_off = rightoff;
|
|
*itup_blkno = BufferGetBlockNumber(rbuf);
|
|
rightoff = OffsetNumberNext(rightoff);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* We have to grab the right sibling (if any) and fix the prev
|
|
* pointer there. We are guaranteed that this is deadlock-free
|
|
* since no other writer will be holding a lock on that page
|
|
* and trying to move left, and all readers release locks on a page
|
|
* before trying to fetch its neighbors.
|
|
*/
|
|
|
|
if (!P_RIGHTMOST(ropaque))
|
|
{
|
|
sbuf = _bt_getbuf(rel, ropaque->btpo_next, BT_WRITE);
|
|
spage = BufferGetPage(sbuf);
|
|
}
|
|
|
|
/*
|
|
* Right sibling is locked, new siblings are prepared, but original
|
|
* page is not updated yet. Log changes before continuing.
|
|
*
|
|
* NO ELOG(ERROR) till right sibling is updated.
|
|
*
|
|
*/
|
|
START_CRIT_CODE;
|
|
{
|
|
char xlbuf[sizeof(xl_btree_split) +
|
|
sizeof(CommandId) + sizeof(RelFileNode) + BLCKSZ];
|
|
xl_btree_split *xlrec = (xl_btree_split*) xlbuf;
|
|
int hsize = SizeOfBtreeSplit;
|
|
int flag = (newitemonleft) ?
|
|
XLOG_BTREE_SPLEFT : XLOG_BTREE_SPLIT;
|
|
BlockNumber blkno;
|
|
XLogRecPtr recptr;
|
|
|
|
xlrec->target.node = rel->rd_node;
|
|
ItemPointerSet(&(xlrec->target.tid), *itup_blkno, *itup_off);
|
|
if (P_ISLEAF(lopaque))
|
|
{
|
|
CommandId cid = GetCurrentCommandId();
|
|
memcpy(xlbuf + hsize, &cid, sizeof(CommandId));
|
|
hsize += sizeof(CommandId);
|
|
memcpy(xlbuf + hsize, &(_xlheapRel->rd_node), sizeof(RelFileNode));
|
|
hsize += sizeof(RelFileNode);
|
|
}
|
|
else
|
|
{
|
|
Size itemsz = IndexTupleDSize(lhikey->bti_itup) +
|
|
(sizeof(BTItemData) - sizeof(IndexTupleData));
|
|
memcpy(xlbuf + hsize, (char*) lhikey, itemsz);
|
|
hsize += itemsz;
|
|
}
|
|
if (newitemonleft)
|
|
{
|
|
/*
|
|
* Read comments in _bt_pgaddtup.
|
|
* Actually, seems that in non-leaf splits newitem shouldn't
|
|
* go to first data key position on left page.
|
|
*/
|
|
if (! P_ISLEAF(lopaque) && *itup_off == P_FIRSTDATAKEY(lopaque))
|
|
{
|
|
BTItemData truncitem = *newitem;
|
|
truncitem.bti_itup.t_info = sizeof(BTItemData);
|
|
memcpy(xlbuf + hsize, &truncitem, sizeof(BTItemData));
|
|
hsize += sizeof(BTItemData);
|
|
}
|
|
else
|
|
{
|
|
Size itemsz = IndexTupleDSize(newitem->bti_itup) +
|
|
(sizeof(BTItemData) - sizeof(IndexTupleData));
|
|
memcpy(xlbuf + hsize, (char*) newitem, itemsz);
|
|
hsize += itemsz;
|
|
}
|
|
blkno = BufferGetBlockNumber(rbuf);
|
|
BlockIdSet(&(xlrec->otherblk), blkno);
|
|
}
|
|
else
|
|
{
|
|
blkno = BufferGetBlockNumber(buf);
|
|
BlockIdSet(&(xlrec->otherblk), blkno);
|
|
}
|
|
|
|
BlockIdSet(&(xlrec->rightblk), ropaque->btpo_next);
|
|
|
|
/*
|
|
* Dirrect access to page is not good but faster - we should
|
|
* implement some new func in page API.
|
|
*/
|
|
recptr = XLogInsert(RM_BTREE_ID, flag, xlbuf,
|
|
hsize, (char*)rightpage + ((PageHeader) rightpage)->pd_upper,
|
|
((PageHeader) rightpage)->pd_special - ((PageHeader) rightpage)->pd_upper);
|
|
|
|
PageSetLSN(leftpage, recptr);
|
|
PageSetSUI(leftpage, ThisStartUpID);
|
|
PageSetLSN(rightpage, recptr);
|
|
PageSetSUI(rightpage, ThisStartUpID);
|
|
if (!P_RIGHTMOST(ropaque))
|
|
{
|
|
PageSetLSN(spage, recptr);
|
|
PageSetSUI(spage, ThisStartUpID);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* 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. Note that this is not a waste of time, since we
|
|
* also require (in the page management code) that the center of a
|
|
* page always be clean, and the most efficient way to guarantee this
|
|
* is just to compact the data by reinserting it into a new left page.
|
|
*/
|
|
|
|
PageRestoreTempPage(leftpage, origpage);
|
|
|
|
if (!P_RIGHTMOST(ropaque))
|
|
{
|
|
sopaque = (BTPageOpaque) PageGetSpecialPointer(spage);
|
|
sopaque->btpo_prev = BufferGetBlockNumber(rbuf);
|
|
|
|
/* write and release the old right sibling */
|
|
_bt_wrtbuf(rel, sbuf);
|
|
}
|
|
END_CRIT_CODE;
|
|
|
|
/* split's done */
|
|
return rbuf;
|
|
}
|
|
|
|
/*
|
|
* _bt_findsplitloc() -- find an appropriate place to split a page.
|
|
*
|
|
* The idea here is to equalize the free space that will be on each split
|
|
* page, *after accounting for the inserted tuple*. (If we fail to account
|
|
* for it, we might find ourselves with too little room on the page that
|
|
* it needs to go into!)
|
|
*
|
|
* We are passed the intended insert position of the new tuple, expressed as
|
|
* the offsetnumber of the tuple it must go in front of. (This could be
|
|
* maxoff+1 if the tuple is to go at the end.)
|
|
*
|
|
* We return the index of the first existing tuple that should go on the
|
|
* righthand page, plus a boolean indicating whether the new tuple goes on
|
|
* the left or right page. The bool is necessary to disambiguate the case
|
|
* where firstright == newitemoff.
|
|
*/
|
|
static OffsetNumber
|
|
_bt_findsplitloc(Relation rel,
|
|
Page page,
|
|
OffsetNumber newitemoff,
|
|
Size newitemsz,
|
|
bool *newitemonleft)
|
|
{
|
|
BTPageOpaque opaque;
|
|
OffsetNumber offnum;
|
|
OffsetNumber maxoff;
|
|
ItemId itemid;
|
|
FindSplitData state;
|
|
int leftspace,
|
|
rightspace,
|
|
goodenough,
|
|
dataitemtotal,
|
|
dataitemstoleft;
|
|
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
|
|
/* Passed-in newitemsz is MAXALIGNED but does not include line pointer */
|
|
newitemsz += sizeof(ItemIdData);
|
|
state.newitemsz = newitemsz;
|
|
state.non_leaf = ! P_ISLEAF(opaque);
|
|
state.have_split = false;
|
|
|
|
/* Total free space available on a btree page, after fixed overhead */
|
|
leftspace = rightspace =
|
|
PageGetPageSize(page) - sizeof(PageHeaderData) -
|
|
MAXALIGN(sizeof(BTPageOpaqueData))
|
|
+ sizeof(ItemIdData);
|
|
|
|
/*
|
|
* Finding the best possible split would require checking all the possible
|
|
* split points, because of the high-key and left-key special cases.
|
|
* That's probably more work than it's worth; instead, stop as soon as
|
|
* we find a "good-enough" split, where good-enough is defined as an
|
|
* imbalance in free space of no more than pagesize/16 (arbitrary...)
|
|
* This should let us stop near the middle on most pages, instead of
|
|
* plowing to the end.
|
|
*/
|
|
goodenough = leftspace / 16;
|
|
|
|
/* The right page will have the same high key as the old page */
|
|
if (!P_RIGHTMOST(opaque))
|
|
{
|
|
itemid = PageGetItemId(page, P_HIKEY);
|
|
rightspace -= (int) (MAXALIGN(ItemIdGetLength(itemid)) +
|
|
sizeof(ItemIdData));
|
|
}
|
|
|
|
/* Count up total space in data items without actually scanning 'em */
|
|
dataitemtotal = rightspace - (int) PageGetFreeSpace(page);
|
|
|
|
/*
|
|
* Scan through the data items and calculate space usage for a split
|
|
* at each possible position.
|
|
*/
|
|
dataitemstoleft = 0;
|
|
maxoff = PageGetMaxOffsetNumber(page);
|
|
|
|
for (offnum = P_FIRSTDATAKEY(opaque);
|
|
offnum <= maxoff;
|
|
offnum = OffsetNumberNext(offnum))
|
|
{
|
|
Size itemsz;
|
|
int leftfree,
|
|
rightfree;
|
|
|
|
itemid = PageGetItemId(page, offnum);
|
|
itemsz = MAXALIGN(ItemIdGetLength(itemid)) + sizeof(ItemIdData);
|
|
|
|
/*
|
|
* We have to allow for the current item becoming the high key of
|
|
* the left page; therefore it counts against left space as well
|
|
* as right space.
|
|
*/
|
|
leftfree = leftspace - dataitemstoleft - (int) itemsz;
|
|
rightfree = rightspace - (dataitemtotal - dataitemstoleft);
|
|
/*
|
|
* Will the new item go to left or right of split?
|
|
*/
|
|
if (offnum > newitemoff)
|
|
_bt_checksplitloc(&state, offnum, leftfree, rightfree,
|
|
true, itemsz);
|
|
else if (offnum < newitemoff)
|
|
_bt_checksplitloc(&state, offnum, leftfree, rightfree,
|
|
false, itemsz);
|
|
else
|
|
{
|
|
/* need to try it both ways! */
|
|
_bt_checksplitloc(&state, offnum, leftfree, rightfree,
|
|
true, itemsz);
|
|
/* here we are contemplating newitem as first on right */
|
|
_bt_checksplitloc(&state, offnum, leftfree, rightfree,
|
|
false, newitemsz);
|
|
}
|
|
|
|
/* Abort scan once we find a good-enough choice */
|
|
if (state.have_split && state.best_delta <= goodenough)
|
|
break;
|
|
|
|
dataitemstoleft += itemsz;
|
|
}
|
|
|
|
/*
|
|
* I believe it is not possible to fail to find a feasible split,
|
|
* but just in case ...
|
|
*/
|
|
if (! state.have_split)
|
|
elog(FATAL, "_bt_findsplitloc: can't find a feasible split point for %s",
|
|
RelationGetRelationName(rel));
|
|
|
|
*newitemonleft = state.newitemonleft;
|
|
return state.firstright;
|
|
}
|
|
|
|
/*
|
|
* Subroutine to analyze a particular possible split choice (ie, firstright
|
|
* and newitemonleft settings), and record the best split so far in *state.
|
|
*/
|
|
static void
|
|
_bt_checksplitloc(FindSplitData *state, OffsetNumber firstright,
|
|
int leftfree, int rightfree,
|
|
bool newitemonleft, Size firstrightitemsz)
|
|
{
|
|
/*
|
|
* Account for the new item on whichever side it is to be put.
|
|
*/
|
|
if (newitemonleft)
|
|
leftfree -= (int) state->newitemsz;
|
|
else
|
|
rightfree -= (int) state->newitemsz;
|
|
/*
|
|
* If we are not on the leaf level, we will be able to discard the
|
|
* key data from the first item that winds up on the right page.
|
|
*/
|
|
if (state->non_leaf)
|
|
rightfree += (int) firstrightitemsz -
|
|
(int) (MAXALIGN(sizeof(BTItemData)) + sizeof(ItemIdData));
|
|
/*
|
|
* If feasible split point, remember best delta.
|
|
*/
|
|
if (leftfree >= 0 && rightfree >= 0)
|
|
{
|
|
int delta = leftfree - rightfree;
|
|
|
|
if (delta < 0)
|
|
delta = -delta;
|
|
if (!state->have_split || delta < state->best_delta)
|
|
{
|
|
state->have_split = true;
|
|
state->newitemonleft = newitemonleft;
|
|
state->firstright = firstright;
|
|
state->best_delta = delta;
|
|
}
|
|
}
|
|
}
|
|
|
|
/*
|
|
* _bt_getstackbuf() -- Walk back up the tree one step, and find the item
|
|
* we last looked at in the parent.
|
|
*
|
|
* This is possible because we save a bit image of the last item
|
|
* we looked at in the parent, and the update algorithm guarantees
|
|
* that if items above us in the tree move, they only move right.
|
|
*
|
|
* Also, re-set bts_blkno & bts_offset if changed.
|
|
*/
|
|
static Buffer
|
|
_bt_getstackbuf(Relation rel, BTStack stack)
|
|
{
|
|
BlockNumber blkno;
|
|
Buffer buf;
|
|
OffsetNumber start,
|
|
offnum,
|
|
maxoff;
|
|
Page page;
|
|
ItemId itemid;
|
|
BTItem item;
|
|
BTPageOpaque opaque;
|
|
|
|
blkno = stack->bts_blkno;
|
|
buf = _bt_getbuf(rel, blkno, BT_WRITE);
|
|
page = BufferGetPage(buf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
maxoff = PageGetMaxOffsetNumber(page);
|
|
|
|
start = stack->bts_offset;
|
|
/*
|
|
* _bt_insertonpg set bts_offset to InvalidOffsetNumber in the
|
|
* case of concurrent ROOT page split. Also, watch out for
|
|
* possibility that page has a high key now when it didn't before.
|
|
*/
|
|
if (start < P_FIRSTDATAKEY(opaque))
|
|
start = P_FIRSTDATAKEY(opaque);
|
|
|
|
for (;;)
|
|
{
|
|
/* see if it's on this page */
|
|
for (offnum = start;
|
|
offnum <= maxoff;
|
|
offnum = OffsetNumberNext(offnum))
|
|
{
|
|
itemid = PageGetItemId(page, offnum);
|
|
item = (BTItem) PageGetItem(page, itemid);
|
|
if (BTItemSame(item, &stack->bts_btitem))
|
|
{
|
|
/* Return accurate pointer to where link is now */
|
|
stack->bts_blkno = blkno;
|
|
stack->bts_offset = offnum;
|
|
return buf;
|
|
}
|
|
}
|
|
/* by here, the item we're looking for moved right at least one page */
|
|
if (P_RIGHTMOST(opaque))
|
|
elog(FATAL, "_bt_getstackbuf: my bits moved right off the end of the world!"
|
|
"\n\tRecreate index %s.", RelationGetRelationName(rel));
|
|
|
|
blkno = opaque->btpo_next;
|
|
_bt_relbuf(rel, buf, BT_WRITE);
|
|
buf = _bt_getbuf(rel, blkno, BT_WRITE);
|
|
page = BufferGetPage(buf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
maxoff = PageGetMaxOffsetNumber(page);
|
|
start = P_FIRSTDATAKEY(opaque);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* _bt_newroot() -- Create a new root page for the index.
|
|
*
|
|
* 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. The new root page is neither pinned nor locked, and
|
|
* we have also written out lbuf and rbuf and dropped their pins/locks.
|
|
*/
|
|
void
|
|
_bt_newroot(Relation rel, Buffer lbuf, Buffer rbuf)
|
|
{
|
|
Buffer rootbuf;
|
|
Page lpage,
|
|
rpage,
|
|
rootpage;
|
|
BlockNumber lbkno,
|
|
rbkno;
|
|
BlockNumber rootblknum;
|
|
BTPageOpaque rootopaque;
|
|
ItemId itemid;
|
|
BTItem item;
|
|
Size itemsz;
|
|
BTItem new_item;
|
|
Buffer metabuf;
|
|
|
|
/* get a new root page */
|
|
rootbuf = _bt_getbuf(rel, P_NEW, BT_WRITE);
|
|
rootpage = BufferGetPage(rootbuf);
|
|
rootblknum = BufferGetBlockNumber(rootbuf);
|
|
metabuf = _bt_getbuf(rel, BTREE_METAPAGE,BT_WRITE);
|
|
|
|
/* NO ELOG(ERROR) from here till newroot op is logged */
|
|
START_CRIT_CODE;
|
|
|
|
/* set btree special data */
|
|
rootopaque = (BTPageOpaque) PageGetSpecialPointer(rootpage);
|
|
rootopaque->btpo_prev = rootopaque->btpo_next = P_NONE;
|
|
rootopaque->btpo_flags |= BTP_ROOT;
|
|
rootopaque->btpo_parent = BTREE_METAPAGE;
|
|
|
|
lbkno = BufferGetBlockNumber(lbuf);
|
|
rbkno = BufferGetBlockNumber(rbuf);
|
|
lpage = BufferGetPage(lbuf);
|
|
rpage = BufferGetPage(rbuf);
|
|
|
|
/*
|
|
* Make sure pages in old root level have valid parent links --- we will
|
|
* need this in _bt_insertonpg() if a concurrent root split happens (see
|
|
* README).
|
|
*/
|
|
((BTPageOpaque) PageGetSpecialPointer(lpage))->btpo_parent =
|
|
((BTPageOpaque) PageGetSpecialPointer(rpage))->btpo_parent =
|
|
rootblknum;
|
|
|
|
/*
|
|
* Create downlink item for left page (old root). Since this will be
|
|
* the first item in a non-leaf page, it implicitly has minus-infinity
|
|
* key value, so we need not store any actual key in it.
|
|
*/
|
|
itemsz = sizeof(BTItemData);
|
|
new_item = (BTItem) palloc(itemsz);
|
|
new_item->bti_itup.t_info = itemsz;
|
|
ItemPointerSet(&(new_item->bti_itup.t_tid), lbkno, P_HIKEY);
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
if (PageAddItem(rootpage, (Item) new_item, itemsz, P_HIKEY, LP_USED) == InvalidOffsetNumber)
|
|
elog(STOP, "btree: failed to add leftkey to new root page");
|
|
pfree(new_item);
|
|
|
|
/*
|
|
* 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);
|
|
itemsz = ItemIdGetLength(itemid);
|
|
item = (BTItem) PageGetItem(lpage, itemid);
|
|
new_item = _bt_formitem(&(item->bti_itup));
|
|
ItemPointerSet(&(new_item->bti_itup.t_tid), rbkno, P_HIKEY);
|
|
|
|
/*
|
|
* insert the right page pointer into the new root page.
|
|
*/
|
|
if (PageAddItem(rootpage, (Item) new_item, itemsz, P_FIRSTKEY, LP_USED) == InvalidOffsetNumber)
|
|
elog(STOP, "btree: failed to add rightkey to new root page");
|
|
pfree(new_item);
|
|
|
|
/* XLOG stuff */
|
|
{
|
|
xl_btree_newroot xlrec;
|
|
Page metapg = BufferGetPage(metabuf);
|
|
BTMetaPageData *metad = BTPageGetMeta(metapg);
|
|
XLogRecPtr recptr;
|
|
|
|
xlrec.node = rel->rd_node;
|
|
BlockIdSet(&(xlrec.rootblk), rootblknum);
|
|
|
|
/*
|
|
* Dirrect access to page is not good but faster - we should
|
|
* implement some new func in page API.
|
|
*/
|
|
recptr = XLogInsert(RM_BTREE_ID, XLOG_BTREE_NEWROOT,
|
|
(char*)&xlrec, SizeOfBtreeNewroot,
|
|
(char*)rootpage + ((PageHeader) rootpage)->pd_upper,
|
|
((PageHeader) rootpage)->pd_special - ((PageHeader) rootpage)->pd_upper);
|
|
|
|
metad->btm_root = rootblknum;
|
|
(metad->btm_level)++;
|
|
|
|
PageSetLSN(rootpage, recptr);
|
|
PageSetSUI(rootpage, ThisStartUpID);
|
|
PageSetLSN(metapg, recptr);
|
|
PageSetSUI(metapg, ThisStartUpID);
|
|
|
|
_bt_wrtbuf(rel, metabuf);
|
|
}
|
|
END_CRIT_CODE;
|
|
|
|
/* write and let go of the new root buffer */
|
|
_bt_wrtbuf(rel, rootbuf);
|
|
|
|
/* update and release new sibling, and finally the old root */
|
|
_bt_wrtbuf(rel, rbuf);
|
|
_bt_wrtbuf(rel, lbuf);
|
|
}
|
|
|
|
/*
|
|
* _bt_pgaddtup() -- add a tuple to a particular page in the index.
|
|
*
|
|
* This routine adds the tuple to the page as requested. It does
|
|
* not affect pin/lock status, but you'd better have a write lock
|
|
* and pin on the target buffer! Don't forget to write and release
|
|
* the buffer afterwards, either.
|
|
*
|
|
* The main difference between this routine and a bare PageAddItem call
|
|
* is that this code knows that the leftmost data item on a non-leaf
|
|
* btree page doesn't need to have a key. Therefore, it strips such
|
|
* items down to just the item header. CAUTION: this works ONLY if
|
|
* we insert the items in order, so that the given itup_off does
|
|
* represent the final position of the item!
|
|
*/
|
|
static void
|
|
_bt_pgaddtup(Relation rel,
|
|
Page page,
|
|
Size itemsize,
|
|
BTItem btitem,
|
|
OffsetNumber itup_off,
|
|
const char *where)
|
|
{
|
|
BTPageOpaque opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
BTItemData truncitem;
|
|
|
|
if (! P_ISLEAF(opaque) && itup_off == P_FIRSTDATAKEY(opaque))
|
|
{
|
|
memcpy(&truncitem, btitem, sizeof(BTItemData));
|
|
truncitem.bti_itup.t_info = sizeof(BTItemData);
|
|
btitem = &truncitem;
|
|
itemsize = sizeof(BTItemData);
|
|
}
|
|
|
|
if (PageAddItem(page, (Item) btitem, itemsize, itup_off,
|
|
LP_USED) == InvalidOffsetNumber)
|
|
elog(STOP, "btree: failed to add item to the %s for %s",
|
|
where, RelationGetRelationName(rel));
|
|
}
|
|
|
|
/*
|
|
* _bt_isequal - used in _bt_doinsert in check for duplicates.
|
|
*
|
|
* This is very similar to _bt_compare, except for NULL handling.
|
|
* Rule is simple: NOT_NULL not equal NULL, NULL not_equal NULL too.
|
|
*/
|
|
static bool
|
|
_bt_isequal(TupleDesc itupdesc, Page page, OffsetNumber offnum,
|
|
int keysz, ScanKey scankey)
|
|
{
|
|
BTItem btitem;
|
|
IndexTuple itup;
|
|
int i;
|
|
|
|
/* Better be comparing to a leaf item */
|
|
Assert(P_ISLEAF((BTPageOpaque) PageGetSpecialPointer(page)));
|
|
|
|
btitem = (BTItem) PageGetItem(page, PageGetItemId(page, offnum));
|
|
itup = &(btitem->bti_itup);
|
|
|
|
for (i = 1; i <= keysz; i++)
|
|
{
|
|
ScanKey entry = &scankey[i - 1];
|
|
AttrNumber attno;
|
|
Datum datum;
|
|
bool isNull;
|
|
int32 result;
|
|
|
|
attno = entry->sk_attno;
|
|
Assert(attno == i);
|
|
datum = index_getattr(itup, attno, itupdesc, &isNull);
|
|
|
|
/* NULLs are never equal to anything */
|
|
if (entry->sk_flags & SK_ISNULL || isNull)
|
|
return false;
|
|
|
|
result = DatumGetInt32(FunctionCall2(&entry->sk_func,
|
|
entry->sk_argument,
|
|
datum));
|
|
|
|
if (result != 0)
|
|
return false;
|
|
}
|
|
|
|
/* if we get here, the keys are equal */
|
|
return true;
|
|
}
|