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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2003-07-29 22:18:48 +0000 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2003-07-29 22:18:48 +0000 |
| commit | a4ffca6bdfea4df003f6ffd044b575fabd7e084b (patch) | |
| tree | eff7eb79e99500ffb925bdb5b0d1226babd3531f /src | |
| parent | 091b9c211c8a3598386f148ca8acb6e6ce2c794a (diff) | |
| download | postgresql-a4ffca6bdfea4df003f6ffd044b575fabd7e084b.tar.gz postgresql-a4ffca6bdfea4df003f6ffd044b575fabd7e084b.zip | |
Fix longstanding error in _bt_search(): should moveright at top of loop not
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.
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/access/nbtree/nbtsearch.c | 20 |
1 files changed, 10 insertions, 10 deletions
diff --git a/src/backend/access/nbtree/nbtsearch.c b/src/backend/access/nbtree/nbtsearch.c index 66f2428cd4a..0b5cf90c63d 100644 --- a/src/backend/access/nbtree/nbtsearch.c +++ b/src/backend/access/nbtree/nbtsearch.c @@ -8,7 +8,7 @@ * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtsearch.c,v 1.72 2002/06/20 20:29:25 momjian Exp $ + * $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtsearch.c,v 1.72.2.1 2003/07/29 22:18:48 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -61,6 +61,13 @@ _bt_search(Relation rel, int keysz, ScanKey scankey, BlockNumber par_blkno; 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 */ page = BufferGetPage(*bufP); opaque = (BTPageOpaque) PageGetSpecialPointer(page); @@ -97,13 +104,6 @@ _bt_search(Relation rel, int keysz, ScanKey scankey, _bt_relbuf(rel, *bufP); *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 */ stack_in = new_stack; } @@ -589,8 +589,8 @@ _bt_first(IndexScanDesc scan, ScanDirection dir) /* * 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 - * greater than the scan key and we know that everything on later - * pages is less than or equal to scan key. + * less than the scan key and we know that everything on later + * pages is greater than or equal to scan key. * * 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 |