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[SPARK-39249][SQL] Improve subexpression elimination for conditional expressions - #36626
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WangGuangxin wants to merge 2 commits into
Closed
[SPARK-39249][SQL] Improve subexpression elimination for conditional expressions#36626WangGuangxin wants to merge 2 commits into
WangGuangxin wants to merge 2 commits into
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WangGuangxin
commented
May 21, 2022
ContributorAuthor
@viirya@cloud-fan Could you please help review this? |
AmplabJenkins
commented
May 21, 2022
Can one of the admins verify this patch? |
Contributor
FYI I created #32987 a while ago to address this in a more general way. I've tried to keep it up to date, but there seemed to be concerns about creating a subexpression for something that might only execute once I guess? Even though that's already happening in certain cases |
WangGuangxin
commented
Jun 6, 2022
ContributorAuthor
@viirya@cloud-fan Could you please help review this? |
We're closing this PR because it hasn't been updated in a while. This isn't a judgement on the merit of the PR in any way. It's just a way of keeping the PR queue manageable. |
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What changes were proposed in this pull request?
Currently we can do subexpression elimination for conditional expressions when the subexpression is common across all
branchGroups. In fact, we can farther improve this when there are common expressions betweenalwaysEvaluatedInputsandbranchGroups.Why are the changes needed?
Take the following case as an example
amay miss subexpression elimination chances since it is not the common expression between allbranchGroups, but it's safe to evaluateaas common subexpression and eagerly execute it since it's part of the prediction, which will always be executed. Ifais a time-expensive expression, we may waste time on running it.This kind of expressions are common when we do
sumon decimal type because of #29026spark/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregate/Sum.scala
Line 125 in 291d155
Many queries on TPC-DS has positive improvement. Following is some obvious improvements on TPC-DS 10T
Does this PR introduce any user-facing change?
No
How was this patch tested?
add more UT.