Riza Suminto has uploaded this change for review. ( http://gerrit.cloudera.org:8080/20040
Change subject: IMPALA-12200: Cap stats NDV from SetOperationStmt.createMetadata ...................................................................... IMPALA-12200: Cap stats NDV from SetOperationStmt.createMetadata Union operator will create merged ColumnStats at SetOperationStmt.createMetadata where it adds all ColumnStats from its input children. One of the stats being accumulated is NDV (num distinct value). There is an opportunity to lower the resulting NDV if all source expression is referring to the same column. This lower NDV can benefit Aggregation node on top of the Union node because it can lower cardinality and memory estimate of the Aggregation node. Testing: - Pass core tests. Change-Id: Ic0bb2eff5005fdfb11adf31499214c63dd552c05 --- M fe/src/main/java/org/apache/impala/analysis/SetOperationStmt.java M fe/src/main/java/org/apache/impala/analysis/SlotDescriptor.java M testdata/workloads/functional-planner/queries/PlannerTest/tpcds-processing-cost.test 3 files changed, 88 insertions(+), 23 deletions(-) git pull ssh://gerrit.cloudera.org:29418/Impala-ASF refs/changes/40/20040/1 -- To view, visit http://gerrit.cloudera.org:8080/20040 To unsubscribe, visit http://gerrit.cloudera.org:8080/settings Gerrit-Project: Impala-ASF Gerrit-Branch: master Gerrit-MessageType: newchange Gerrit-Change-Id: Ic0bb2eff5005fdfb11adf31499214c63dd552c05 Gerrit-Change-Number: 20040 Gerrit-PatchSet: 1 Gerrit-Owner: Riza Suminto <[email protected]>
