Shant Hovsepian has uploaded this change for review. (
http://gerrit.cloudera.org:8080/16349
Change subject: IMPALA-7310: Partial fix for NDV cardinality with NULLs.
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IMPALA-7310: Partial fix for NDV cardinality with NULLs.
This fix just handles the case where a column's cardinality is zero
however it's nullable and we have null stats to indicate there are null
values, therefore we adjust the cardinality from 0 to 1.
The cardinality of zero was especially problematic when calculating
cardinalities for multiple predicates with multiplication. The 0 would
propagate up the plan tree and result in poor plan choices such as
always using broadcast joins where shuffle would've been more optimal.
Testing:
* 26 Node TPC-DS 30TB run had better plans for Q4 and Q11
- Q4 172s -> 80s
- Q11 103s -> 77s
Change-Id: Iec967053b4991f8c67cde62adf003cbd3f429032
---
M fe/src/main/java/org/apache/impala/analysis/SlotRef.java
M fe/src/test/java/org/apache/impala/analysis/ExprNdvTest.java
M testdata/workloads/functional-planner/queries/PlannerTest/tpcds/tpcds-q04.test
M testdata/workloads/functional-planner/queries/PlannerTest/tpcds/tpcds-q11.test
4 files changed, 751 insertions(+), 731 deletions(-)
git pull ssh://gerrit.cloudera.org:29418/Impala-ASF refs/changes/49/16349/1
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Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-MessageType: newchange
Gerrit-Change-Id: Iec967053b4991f8c67cde62adf003cbd3f429032
Gerrit-Change-Number: 16349
Gerrit-PatchSet: 1
Gerrit-Owner: Shant Hovsepian <[email protected]>
