database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-12-19 17:02:53 +03:00
Code Activity

Support "Right Semi Join" plan shapes

Browse Source 
Hash joins can support semijoin with the LHS input on the right, using
the existing logic for inner join, combined with the assurance that only
the first match for each inner tuple is considered, which can be
achieved by leveraging the HEAP_TUPLE_HAS_MATCH flag.  This can be very
useful in some cases since we may now have the option to hash the
smaller table instead of the larger.

Merge join could likely support "Right Semi Join" too.  However, the
benefit of swapping inputs tends to be small here, so we do not address
that in this patch.

Note that this patch also modifies a test query in join.sql to ensure it
continues testing as intended.  With this patch the original query would
result in a right-semi-join rather than semi-join, compromising its
original purpose of testing the fix for neqjoinsel's behavior for
semi-joins.

Author: Richard Guo
Reviewed-by: wenhui qiu, Alena Rybakina, Japin Li
Discussion: https://postgr.es/m/CAMbWs4_X1mN=ic+SxcyymUqFx9bB8pqSLTGJ-F=MHy4PW3eRXw@mail.gmail.com
This commit is contained in:
Richard Guo
2024-07-05 09:26:48 +09:00
parent 5a519abedd
commit aa86129e19
14 changed files with 222 additions and 173 deletions
Download Patch File Download Diff File Expand all files Collapse all files

6
src/include/nodes/pathnodes.h
View File

@@ -2823,9 +2823,9 @@ typedef struct PlaceHolderVar
* min_lefthand and min_righthand for higher joins.)
*
* jointype is never JOIN_RIGHT; a RIGHT JOIN is handled by switching
* the inputs to make it a LEFT JOIN. It's never JOIN_RIGHT_ANTI either.
* So the allowed values of jointype in a join_info_list member are only
* LEFT, FULL, SEMI, or ANTI.
* the inputs to make it a LEFT JOIN. It's never JOIN_RIGHT_SEMI or
* JOIN_RIGHT_ANTI either. So the allowed values of jointype in a
* join_info_list member are only LEFT, FULL, SEMI, or ANTI.
*
* ojrelid is the RT index of the join RTE representing this outer join,
* if there is one. It is zero when jointype is INNER or SEMI, and can be