Qifan Chen has submitted this change and it was merged. ( http://gerrit.cloudera.org:8080/18023 )
Change subject: IMPALA-7942 (part 2): Add query hints for predicate selectivities ...................................................................... IMPALA-7942 (part 2): Add query hints for predicate selectivities Currently, Impala only uses simple estimation to compute selectivity. For some predicates, this may lead to worse query plan due to CBO. This patch adds a new query hint: 'SELECTIVITY' to help specify a selectivity value for a predicate. The parser will interpret expressions wrapped in () followed by a C-style comment /* <predicate hint> */ as a predicate hint. The predicate hint currently can be in the form of +SELECTIVITY(f) where 'f' is a positive floating point number, in the range of (0, 1], to use as the selectivity for the preceding expression. Single predicate example: select col from t where (a=1) /* +SELECTIVITY(0.5) */; Compound predicate example: select col from t where (a=1 or b=2) /* +SELECTIVITY(0.5) */; As a limitation of this path, the selectivity hints for 'AND' compound predicates, either in the original SQL query or internally generated, are ignored. We may supported this in the near future. Testing: - Added new fe tests in 'PlannerTest' - Added new fe tests in 'AnalyzeStmtsTest' for negative cases Change-Id: I2776b9bbd878b8a21d9c866b400140a454f59e1b Reviewed-on: http://gerrit.cloudera.org:8080/18023 Tested-by: Impala Public Jenkins <impala-public-jenk...@cloudera.com> Reviewed-by: Qifan Chen <qfc...@hotmail.com> --- M fe/src/main/cup/sql-parser.cup M fe/src/main/java/org/apache/impala/analysis/BinaryPredicate.java M fe/src/main/java/org/apache/impala/analysis/CompoundPredicate.java M fe/src/main/java/org/apache/impala/analysis/InPredicate.java M fe/src/main/java/org/apache/impala/analysis/IsNullPredicate.java M fe/src/main/java/org/apache/impala/analysis/Predicate.java M fe/src/main/jflex/sql-scanner.flex M fe/src/test/java/org/apache/impala/analysis/AnalyzeStmtsTest.java M fe/src/test/java/org/apache/impala/planner/PlannerTest.java A testdata/workloads/functional-planner/queries/PlannerTest/predicate-selectivity-hint.test 10 files changed, 414 insertions(+), 5 deletions(-) Approvals: Impala Public Jenkins: Verified Qifan Chen: Looks good to me, approved -- 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: merged Gerrit-Change-Id: I2776b9bbd878b8a21d9c866b400140a454f59e1b Gerrit-Change-Number: 18023 Gerrit-PatchSet: 36 Gerrit-Owner: wangsheng <sky...@163.com> Gerrit-Reviewer: Amogh Margoor <amarg...@gmail.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: Xiang Yang <yx91...@126.com> Gerrit-Reviewer: Zoltan Borok-Nagy <borokna...@cloudera.com> Gerrit-Reviewer: wangsheng <sky...@163.com>
