database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-08-24 09:27:52 +03:00
Code Activity

Fix right-semi-joins in HashJoin rescans

Browse Source 
When resetting a HashJoin node for rescans, if it is a single-batch
join and there are no parameter changes for the inner subnode, we can
just reuse the existing hash table without rebuilding it.  However,
for join types that depend on the inner-tuple match flags in the hash
table, we need to reset these match flags to avoid incorrect results.
This applies to right, right-anti, right-semi, and full joins.

When I introduced "Right Semi Join" plan shapes in aa86129e1, I failed
to reset the match flags in the hash table for right-semi joins in
rescans.  This oversight has been shown to produce incorrect results.
This patch fixes it.

Author: Richard Guo
Discussion: https://postgr.es/m/CAMbWs4-nQF9io2WL2SkD0eXvfPdyBc9Q=hRwfQHCGV2usa0jyA@mail.gmail.com
This commit is contained in:
Richard Guo
2024-12-09 20:36:23 +09:00
parent f0c569d715
commit 5668a857de
3 changed files with 97 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
src/backend/executor/nodeHashjoin.c
View File

@@ -1511,10 +1511,11 @@ ExecReScanHashJoin(HashJoinState *node)
/*
* Okay to reuse the hash table; needn't rescan inner, either.
*
* However, if it's a right/right-anti/full join, we'd better
* reset the inner-tuple match flags contained in the table.
* However, if it's a right/right-anti/right-semi/full join, we'd
* better reset the inner-tuple match flags contained in the
* table.
*/
if (HJ_FILL_INNER(node))
if (HJ_FILL_INNER(node) || node->js.jointype == JOIN_RIGHT_SEMI)
ExecHashTableResetMatchFlags(node->hj_HashTable);
/*