Fix GIN posting tree page deletion with incomplete splits. GIN posting tree page deletion failed to consider whether the target page's left sibling page, or the deletion target itself, was marked as incompletely split. Page deletion finds the target page's left sibling by walking the parent's downlinks, but an incompletely split page's new right half is part of the sibling chain despite having no downlink. Deletion could therefore overwrite the rightlink of the wrong page, disconnecting the split's still-live right half from the sibling chain. Scans would then silently miss tuples from that page.
To fix, teach the relevant page deletion path to avoid deleting a posting tree page whose left sibling is marked incompletely split (and to avoid doing so when the target page itself is so marked). This is essentially the same approach used by nbtree page deletion. Claude Code found this problem. The committed test case is a simplified version of the one that it wrote to demonstrate this bug. Author: Peter Geoghegan <[email protected]> Reviewed-by: Andrey Borodin <[email protected]> Discussion: https://postgr.es/m/CAH2-Wz=skjcn+otfvn9rdg+ps9e4cuqwnp-9t12ue2d8neg...@mail.gmail.com Backpatch-through: 14 Branch ------ REL_19_STABLE Details ------- https://git.postgresql.org/pg/commitdiff/b13fd289988067dd09ccc08243fcab803804595b Modified Files -------------- src/backend/access/gin/ginvacuum.c | 18 +++- src/test/modules/gin/Makefile | 2 +- .../modules/gin/expected/gin_incomplete_splits.out | 109 ++++++++++++++++++++- src/test/modules/gin/sql/gin_incomplete_splits.sql | 83 +++++++++++++++- 4 files changed, 206 insertions(+), 6 deletions(-)
