Csaba Ringhofer has posted comments on this change. ( http://gerrit.cloudera.org:8080/18862 )
Change subject: IMPALA-11485: Pushdown LIMIT through UNION and LEFT/RIGHT OUTER JOIN ...................................................................... Patch Set 5: (2 comments) Started looking at the change, first from the aspect of correctness. Thanks for working on this, great optimization! http://gerrit.cloudera.org:8080/#/c/18862/5/fe/src/main/java/org/apache/impala/planner/SingleNodePlanner.java File fe/src/main/java/org/apache/impala/planner/SingleNodePlanner.java: http://gerrit.cloudera.org:8080/#/c/18862/5/fe/src/main/java/org/apache/impala/planner/SingleNodePlanner.java@368 PS5, Line 368: UNION Shouldn't we push down LIMIT for UNION ALL only, and not for UNION? UNION also filters duplicates for children, so a child that returns 1000 rows may lead to only 1 row in the output. http://gerrit.cloudera.org:8080/#/c/18862/5/testdata/workloads/functional-planner/queries/PlannerTest/limit-pushdown-union.test File testdata/workloads/functional-planner/queries/PlannerTest/limit-pushdown-union.test: http://gerrit.cloudera.org:8080/#/c/18862/5/testdata/workloads/functional-planner/queries/PlannerTest/limit-pushdown-union.test@8 PS5, Line 8: limit 5; Can you also add a test with an OFFSET clause? I think that we should push down LIMIT + OFFSET as limit in that case, as simply pushing down limit can lead to returning too few rows from child nodes. -- To view, visit http://gerrit.cloudera.org:8080/18862 To unsubscribe, visit http://gerrit.cloudera.org:8080/settings Gerrit-Project: Impala-ASF Gerrit-Branch: master Gerrit-MessageType: comment Gerrit-Change-Id: Ia5d040c0a98e60639d7ce4b25ecf07a859c8a32c Gerrit-Change-Number: 18862 Gerrit-PatchSet: 5 Gerrit-Owner: Baike Xia <[email protected]> Gerrit-Reviewer: Aman Sinha <[email protected]> Gerrit-Reviewer: Baike Xia <[email protected]> Gerrit-Reviewer: Csaba Ringhofer <[email protected]> Gerrit-Reviewer: Impala Public Jenkins <[email protected]> Gerrit-Reviewer: Jian Zhang <[email protected]> Gerrit-Reviewer: Quanlong Huang <[email protected]> Gerrit-Comment-Date: Sun, 09 Oct 2022 18:58:02 +0000 Gerrit-HasComments: Yes
