mirror/postgresql
2
0
Fork 0
mirror of https://git.postgresql.org/git/postgresql.git synced 2024-12-21 08:29:39 +08:00
Code Issues Packages Projects Releases Wiki Activity

Fix longstanding error in _bt_search(): should moveright at top of loop not

Browse Source 
bottom.  Otherwise we fail to moveright when the root page was split while
we were "in flight" to it.  This is not a significant problem when the root
is above the leaf level, but if the root was also a leaf (ie, a single-page
index just got split) we may return the wrong leaf page to the caller,
resulting in failure to find a key that is in fact present.  Bug has existed
at least since 7.1, probably forever.
This commit is contained in:
Tom Lane 2003-07-29 22:18:53 +00:00
parent 90011a8918
commit 5925377401
1 changed files with 10 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
src/backend/access/nbtree/nbtsearch.c
View File

@ -8,7 +8,7 @@
* Portions Copyright (c) 1994, Regents of the University of California * Portions Copyright (c) 1994, Regents of the University of California
* *
* IDENTIFICATION * IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtsearch.c,v 1.69 2001/10/25 05:49:21 momjian Exp $ * $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtsearch.c,v 1.69.2.1 2003/07/29 22:18:53 tgl Exp $
* *
*------------------------------------------------------------------------- *-------------------------------------------------------------------------
*/ */
@ -61,6 +61,13 @@ _bt_search(Relation rel, int keysz, ScanKey scankey,
BlockNumber par_blkno; BlockNumber par_blkno;
BTStack new_stack; BTStack new_stack;
/*
* Race -- the page we just grabbed may have split since we read
* its pointer in the parent (or metapage). If it has, we may need
* to move right to its new sibling. Do that.
*/
*bufP = _bt_moveright(rel, *bufP, keysz, scankey, BT_READ);
/* if this is a leaf page, we're done */ /* if this is a leaf page, we're done */
page = BufferGetPage(*bufP); page = BufferGetPage(*bufP);
opaque = (BTPageOpaque) PageGetSpecialPointer(page); opaque = (BTPageOpaque) PageGetSpecialPointer(page);
@ -97,13 +104,6 @@ _bt_search(Relation rel, int keysz, ScanKey scankey,
_bt_relbuf(rel, *bufP); _bt_relbuf(rel, *bufP);
*bufP = _bt_getbuf(rel, blkno, BT_READ); *bufP = _bt_getbuf(rel, blkno, BT_READ);
/*
* Race -- the page we just grabbed may have split since we read
* its pointer in the parent. If it has, we may need to move
* right to its new sibling. Do that.
*/
*bufP = _bt_moveright(rel, *bufP, keysz, scankey, BT_READ);
/* okay, all set to move down a level */ /* okay, all set to move down a level */
stack_in = new_stack; stack_in = new_stack;
} }
@ -590,8 +590,8 @@ _bt_first(IndexScanDesc scan, ScanDirection dir)
/* /*
* At this point we are positioned at the first item >= scan key, or * At this point we are positioned at the first item >= scan key, or
* possibly at the end of a page on which all the existing items are * possibly at the end of a page on which all the existing items are
* greater than the scan key and we know that everything on later * less than the scan key and we know that everything on later
* pages is less than or equal to scan key. * pages is greater than or equal to scan key.
* *
* We could step forward in the latter case, but that'd be a waste of * We could step forward in the latter case, but that'd be a waste of
* time if we want to scan backwards. So, it's now time to examine * time if we want to scan backwards. So, it's now time to examine