From 7afca7edef751b8d7c0f5b6402ffcefc11c67fdd Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas Date: Fri, 4 Apr 2025 13:49:00 +0300 Subject: [PATCH] Relax assertion in finding correct GiST parent Commit 28d3c2ddcf introduced an assertion that if the memorized downlink location in the insertion stack isn't valid, the parent's LSN should've changed too. Turns out that was too strict. In gistFindCorrectParent(), if we walk right, we update the parent's block number and clear its memorized 'downlinkoffnum'. That triggered the assertion on next call to gistFindCorrectParent(), if the parent needed to be split too. Relax the assertion, so that it's OK if downlinkOffnum is InvalidOffsetNumber. Backpatch to v13-, all supported versions. The assertion was added in commit 28d3c2ddcf in v12. Reported-by: Alexander Lakhin Reviewed-by: Tender Wang Discussion: https://www.postgresql.org/message-id/18396-03cac9beb2f7aac3@postgresql.org --- src/backend/access/gist/gist.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) diff --git a/src/backend/access/gist/gist.c b/src/backend/access/gist/gist.c index 1840f04bfbf..7b24380c978 100644 --- a/src/backend/access/gist/gist.c +++ b/src/backend/access/gist/gist.c @@ -1048,12 +1048,19 @@ gistFindCorrectParent(Relation r, GISTInsertStack *child, bool is_build) /* * The page has changed since we looked. During normal operation, every * update of a page changes its LSN, so the LSN we memorized should have - * changed too. During index build, however, we don't WAL-log the changes - * until we have built the index, so the LSN doesn't change. There is no - * concurrent activity during index build, but we might have changed the - * parent ourselves. + * changed too. + * + * During index build, however, we don't WAL-log the changes until we have + * built the index, so the LSN doesn't change. There is no concurrent + * activity during index build, but we might have changed the parent + * ourselves. + * + * We will also get here if child->downlinkoffnum is invalid. That happens + * if 'parent' had been updated by an earlier call to this function on its + * grandchild, which had to move right. */ - Assert(parent->lsn != PageGetLSN(parent->page) || is_build); + Assert(parent->lsn != PageGetLSN(parent->page) || is_build || + child->downlinkoffnum == InvalidOffsetNumber); /* * Scan the page to re-find the downlink. If the page was split, it might