From caca6d8d276ce57473e97050d19dfe84e59482c8 Mon Sep 17 00:00:00 2001 From: Peter Geoghegan Date: Fri, 8 Nov 2024 16:34:41 -0500 Subject: [PATCH] Assert consistency of currPage that ended scan. When _bt_readnextpage is called with our nbtree parallel scan already seized (i.e. when it is directly called by _bt_first), we never expect a prior call to _bt_readpage for lastcurrblkno to already indicate that the scan should end -- the _bt_first caller's blkno must always be read. After all, the "prior" _bt_readpage call (the call for lastcurrblkno) probably took place in some other backend (and it might not even have finished by the time our backend reaches _bt_first/_bt_readnextpage). Add a documenting assertion to the path where _bt_readnextpage ends the parallel scan based on information about lastcurrblkno from so->currPos. Assert that the most recent _bt_readpage call that set so->currPos is in fact lastcurrblkno's _bt_readpage call. Follow-up to bugfix commit b5ee4e52. --- src/backend/access/nbtree/nbtsearch.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/src/backend/access/nbtree/nbtsearch.c b/src/backend/access/nbtree/nbtsearch.c index ebb6c108367..2786a8564f2 100644 --- a/src/backend/access/nbtree/nbtsearch.c +++ b/src/backend/access/nbtree/nbtsearch.c @@ -2230,8 +2230,9 @@ _bt_readnextpage(IndexScanDesc scan, BlockNumber blkno, !so->currPos.moreRight : !so->currPos.moreLeft)) { /* most recent _bt_readpage call (for lastcurrblkno) ended scan */ + Assert(so->currPos.currPage == lastcurrblkno && !seized); BTScanPosInvalidate(so->currPos); - _bt_parallel_done(scan); + _bt_parallel_done(scan); /* iff !so->needPrimScan */ return false; } -- 2.30.2