Kurt Deschler has posted comments on this change. ( http://gerrit.cloudera.org:8080/18023 )
Change subject: IMPALA-7942 (part 2): Add query hints for predicate selectivities ...................................................................... Patch Set 23: (8 comments) http://gerrit.cloudera.org:8080/#/c/18023/23//COMMIT_MSG Commit Message: http://gerrit.cloudera.org:8080/#/c/18023/23//COMMIT_MSG@11 PS23, Line 11: Hence, we add new hints to reduce such errors. Maybe in the future, No need to mention histograms here. Instead just say this is giving a qay to override estimates. http://gerrit.cloudera.org:8080/#/c/18023/23//COMMIT_MSG@14 PS23, Line 14: another Don't say another unless you want to qualify that means http://gerrit.cloudera.org:8080/#/c/18023/23//COMMIT_MSG@15 PS23, Line 15: hint to original selectivity computing. Describe the syntax additions here at a high level. i.e. The parser will interpret expressions wrapped in () followed by a C-style /* comment */ as a predicate hint. The predicate hint currently supports +SELECTIVITY(f) where 'f' is a positive floating point number to use as the selectivity for the preceding expression. http://gerrit.cloudera.org:8080/#/c/18023/23//COMMIT_MSG@17 PS23, Line 17: Format like this: Single predicate example: http://gerrit.cloudera.org:8080/#/c/18023/23//COMMIT_MSG@21 PS23, Line 21: Besides, this hint is also valid for compound predicate like this: Compound Predicate Example: http://gerrit.cloudera.org:8080/#/c/18023/23//COMMIT_MSG@25 PS23, Line 25: But pay attention, if we want to use 'SELECTIVITY' hint for predicate, State this first when you are describing the general syntax. http://gerrit.cloudera.org:8080/#/c/18023/23/fe/src/main/java/org/apache/impala/analysis/Expr.java File fe/src/main/java/org/apache/impala/analysis/Expr.java: http://gerrit.cloudera.org:8080/#/c/18023/23/fe/src/main/java/org/apache/impala/analysis/Expr.java@1068 PS23, Line 1068: && !((CompoundPredicate) this).selectivityValidHintSet()) { Skipping child conjuncts here based on a hint does not seem legal http://gerrit.cloudera.org:8080/#/c/18023/23/fe/src/main/java/org/apache/impala/rewrite/BetweenToCompoundRule.java File fe/src/main/java/org/apache/impala/rewrite/BetweenToCompoundRule.java: http://gerrit.cloudera.org:8080/#/c/18023/23/fe/src/main/java/org/apache/impala/rewrite/BetweenToCompoundRule.java@70 PS23, Line 70: result.setSelectivityHint(bp.getSelectivity()); Probably better to no propagate the selectivity. If user want it to apply across predicates, they should be able to wrap them in a () block. -- To view, visit http://gerrit.cloudera.org:8080/18023 To unsubscribe, visit http://gerrit.cloudera.org:8080/settings Gerrit-Project: Impala-ASF Gerrit-Branch: master Gerrit-MessageType: comment Gerrit-Change-Id: I2776b9bbd878b8a21d9c866b400140a454f59e1b Gerrit-Change-Number: 18023 Gerrit-PatchSet: 23 Gerrit-Owner: wangsheng <sky...@163.com> Gerrit-Reviewer: Amogh Margoor <amarg...@gmail.com> Gerrit-Reviewer: Fucun Chu <chufu...@hotmail.com> Gerrit-Reviewer: Impala Public Jenkins <impala-public-jenk...@cloudera.com> Gerrit-Reviewer: Kurt Deschler <kdesc...@cloudera.com> Gerrit-Reviewer: Qifan Chen <qfc...@hotmail.com> Gerrit-Reviewer: Quanlong Huang <huangquanl...@gmail.com> Gerrit-Reviewer: Yifan Zhang <chinazhangyi...@163.com> Gerrit-Reviewer: Zoltan Borok-Nagy <borokna...@cloudera.com> Gerrit-Reviewer: wangsheng <sky...@163.com> Gerrit-Comment-Date: Fri, 24 Mar 2023 19:57:45 +0000 Gerrit-HasComments: Yes
