diff options
| author | Peter Geoghegan | 2025-12-11 01:50:47 +0000 |
|---|---|---|
| committer | Peter Geoghegan | 2025-12-11 01:50:47 +0000 |
| commit | e16c6f024718cf854f5b76a4a2ed402f1a7911f1 (patch) | |
| tree | 64614fde92dfead6be3ba21271b828083beff9e0 /src | |
| parent | 06761b6096b661e838512e3a83f71345b59710b9 (diff) | |
Clarify why _bt_killitems sorts its items array.
Make it clear why _bt_killitems sorts the scan's so->killedItems[]
array. Also add an assertion to the _bt_killitems loop (that iterates
through this array) to verify it accesses tuples in leaf page order.
Follow-up to commit bfb335df58.
Author: Peter Geoghegan <pg@bowt.ie>
Suggested-by: Victor Yegorov <vyegorov@gmail.com>
Discussion: https://postgr.es/m/CAGnEboirgArezZDNeFrR8FOGvKF-Xok333s2iVwWi65gZf8MEA@mail.gmail.com
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/access/nbtree/nbtutils.c | 13 |
1 files changed, 9 insertions, 4 deletions
diff --git a/src/backend/access/nbtree/nbtutils.c b/src/backend/access/nbtree/nbtutils.c index 16e23a517b2..a451d48e11e 100644 --- a/src/backend/access/nbtree/nbtutils.c +++ b/src/backend/access/nbtree/nbtutils.c @@ -222,11 +222,12 @@ _bt_killitems(IndexScanDesc scan) so->numKilled = 0; /* - * so->killedItems[] is in whatever order the scan returned items in. - * Items will appear in descending order during backwards scans. And - * scrollable cursor scans might have duplicate items. + * We need to iterate through so->killedItems[] in leaf page order; the + * loop below expects this (when marking posting list tuples, at least). + * so->killedItems[] is now in whatever order the scan returned items in. + * Scrollable cursor scans might have even saved the same item/TID twice. * - * Sort and uniqueify so->killedItems[] to deal with all this. + * Sort and unique-ify so->killedItems[] to deal with all this. */ if (numKilled > 1) { @@ -271,6 +272,7 @@ _bt_killitems(IndexScanDesc scan) minoff = P_FIRSTDATAKEY(opaque); maxoff = PageGetMaxOffsetNumber(page); + /* Iterate through so->killedItems[] in leaf page order */ for (int i = 0; i < numKilled; i++) { int itemIndex = so->killedItems[i]; @@ -279,6 +281,9 @@ _bt_killitems(IndexScanDesc scan) Assert(itemIndex >= so->currPos.firstItem && itemIndex <= so->currPos.lastItem); + Assert(i == 0 || + offnum >= so->currPos.items[so->killedItems[i - 1]].indexOffset); + if (offnum < minoff) continue; /* pure paranoia */ while (offnum <= maxoff) |