1. _bt_compare fixed to work properly with new code in _bt_insertonpg
(old _bt_compare always returned >= 0 while comparing with P_HIKEY on root page - it breaks root page when _bt_insertonpg tries insert new minimal key into root page). 2. Fixed bug concerns "empty" pages: non-rightmost pages with only P_HIKEY present on it. Such pages appear after vacuum.
This commit is contained in:
Vadim B. Mikheev
parent
64397b758f
commit
c3e10a4caf
@ -7,7 +7,7 @@
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtsearch.c,v 1.10 1996/11/21 06:10:55 vadim Exp $
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* $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtsearch.c,v 1.11 1996/12/06 09:41:45 vadim Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -409,9 +409,19 @@ _bt_firsteq(Relation rel,
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* 0 if scankey == tuple at offnum;
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* +1 if scankey > tuple at offnum.
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*
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* -- Old comments:
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* In order to avoid having to propagate changes up the tree any time
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* a new minimal key is inserted, the leftmost entry on the leftmost
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* page is less than all possible keys, by definition.
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*
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* -- New ones:
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* New insertion code (fix against updating _in_place_ if new minimal
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* key has bigger size than old one) may delete P_HIKEY entry on the
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* root page in order to insert new minimal key - and so this definition
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* does not work properly in this case and breaks key' order on root
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* page. BTW, this propagation occures only while page' splitting,
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* but not "any time a new min key is inserted" (see _bt_insertonpg).
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* - vadim 12/05/96
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*/
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int
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_bt_compare(Relation rel,
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@ -436,6 +446,8 @@ _bt_compare(Relation rel,
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* If this is a leftmost internal page, and if our comparison is
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* with the first key on the page, then the item at that position is
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* by definition less than the scan key.
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*
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* - see new comments above...
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*/
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opaque = (BTPageOpaque) PageGetSpecialPointer(page);
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@ -453,12 +465,20 @@ _bt_compare(Relation rel,
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* well as the rightmost page. but that implies that this
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* code path only applies to the root -- which seems
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* unlikely..
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*
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* - see new comments above...
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*/
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if (! P_RIGHTMOST(opaque)) {
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elog(WARN, "_bt_compare: invalid comparison to high key");
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}
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#ifdef 0
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/*
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* We just have to belive that right answer will not
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* break anything. I've checked code and all seems to be ok.
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* See new comments above...
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*
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* -- Old comments
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* If the item on the page is equal to the scankey, that's
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* okay to admit. We just can't claim that the first key on
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* the page is greater than anything.
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@ -469,6 +489,7 @@ _bt_compare(Relation rel,
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return (0);
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}
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return (1);
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#endif
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}
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btitem = (BTItem) PageGetItem(page, PageGetItemId(page, offnum));
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@ -601,6 +622,7 @@ _bt_first(IndexScanDesc scan, ScanDirection dir)
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Page page;
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BTStack stack;
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OffsetNumber offnum, maxoff;
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bool offGmax = false;
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BTItem btitem;
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IndexTuple itup;
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ItemPointer current;
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@ -665,7 +687,10 @@ _bt_first(IndexScanDesc scan, ScanDirection dir)
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maxoff = PageGetMaxOffsetNumber(page);
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if (offnum > maxoff)
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{
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offnum = maxoff;
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offGmax = true;
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}
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blkno = BufferGetBlockNumber(buf);
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ItemPointerSet(current, blkno, offnum);
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@ -736,10 +761,21 @@ _bt_first(IndexScanDesc scan, ScanDirection dir)
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if (result > 0)
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(void) _bt_twostep(scan, &buf, ForwardScanDirection);
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}
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else if ( offGmax && result > 0 )
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{ /*
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* Just remember: _bt_binsrch() returns the OffsetNumber of
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* the first matching key on the page, or the OffsetNumber at
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* which the matching key WOULD APPEAR IF IT WERE on this page.
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* No key on this page, but offnum from _bt_binsrch() greater
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* maxoff - have to move right. - vadim 12/06/96
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*/
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(void) _bt_twostep(scan, &buf, ForwardScanDirection);
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}
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break;
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case BTGreaterStrategyNumber:
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if (result >= 0) {
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/* offGmax helps as above */
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if (result >= 0 || offGmax) {
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do {
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if (!_bt_twostep(scan, &buf, ForwardScanDirection))
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break;
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@ -1084,13 +1120,17 @@ _bt_endpoint(IndexScanDesc scan, ScanDirection dir)
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maxoff = PageGetMaxOffsetNumber(page);
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if (ScanDirectionIsForward(dir)) {
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if (PageIsEmpty(page)) {
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maxoff = FirstOffsetNumber;
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} else {
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maxoff = PageGetMaxOffsetNumber(page);
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}
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if ( !P_LEFTMOST(opaque) ) /* non-leftmost page ? */
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elog (WARN, "_bt_endpoint: leftmost page (%u) has not leftmost flag", blkno);
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start = P_RIGHTMOST(opaque) ? P_HIKEY : P_FIRSTKEY;
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/*
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* I don't understand this stuff! It doesn't work for non-rightmost
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* pages with only one element (P_HIKEY) which we have after
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* deletion itups by vacuum (it's case of start > maxoff).
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* Scanning in BackwardScanDirection is not understandable at all.
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* Well - new stuff. - vadim 12/06/96
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*/
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#ifdef 0
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if (PageIsEmpty(page) || start > maxoff) {
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ItemPointerSet(current, blkno, maxoff);
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if (!_bt_step(scan, &buf, BackwardScanDirection))
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@ -1098,10 +1138,35 @@ _bt_endpoint(IndexScanDesc scan, ScanDirection dir)
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start = ItemPointerGetOffsetNumber(current);
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page = BufferGetPage(buf);
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} else {
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}
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#endif
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if ( PageIsEmpty (page) )
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{
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if ( start != P_HIKEY ) /* non-rightmost page */
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elog (WARN, "_bt_endpoint: non-rightmost page (%u) is empty", blkno);
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/* It's left- & right- most page - root page, - and it's empty... */
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return ((RetrieveIndexResult) NULL);
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}
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if ( start > maxoff ) /* start == 2 && maxoff == 1 */
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{
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ItemPointerSet(current, blkno, maxoff);
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if (!_bt_step(scan, &buf, ForwardScanDirection))
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return ((RetrieveIndexResult) NULL);
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start = ItemPointerGetOffsetNumber(current);
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page = BufferGetPage(buf);
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}
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/* new stuff ends here */
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else {
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ItemPointerSet(current, blkno, start);
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}
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} else if (ScanDirectionIsBackward(dir)) {
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/*
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* I don't understand this stuff too! If RIGHT-most leaf page is
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* empty why do scanning in ForwardScanDirection ???
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* Well - new stuff. - vadim 12/06/96
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*/
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#ifdef 0
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if (PageIsEmpty(page)) {
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ItemPointerSet(current, blkno, FirstOffsetNumber);
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if (!_bt_step(scan, &buf, ForwardScanDirection))
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@ -1109,7 +1174,23 @@ _bt_endpoint(IndexScanDesc scan, ScanDirection dir)
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start = ItemPointerGetOffsetNumber(current);
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page = BufferGetPage(buf);
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} else {
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}
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#endif
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if (PageIsEmpty(page))
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{
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/* If it's leftmost page too - it's empty root page... */
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if ( P_LEFTMOST(opaque) )
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return ((RetrieveIndexResult) NULL);
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/* Go back ! */
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ItemPointerSet(current, blkno, FirstOffsetNumber);
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if (!_bt_step(scan, &buf, BackwardScanDirection))
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return ((RetrieveIndexResult) NULL);
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start = ItemPointerGetOffsetNumber(current);
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page = BufferGetPage(buf);
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}
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/* new stuff ends here */
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else {
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start = PageGetMaxOffsetNumber(page);
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ItemPointerSet(current, blkno, start);
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}
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