[SPARK-35449][SQL][3.1] Only extract common expressions from CaseWhen values if elseValue is set #32651
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viirya
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May 24, 2021
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cc @dongjoon-hyun as this touches branch-3.1. |
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Thank you, @viirya . |
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Thanks all! Merging to branch-3.1. |
viirya
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May 24, 2021
… values if elseValue is set ### What changes were proposed in this pull request? This PR fixes a bug with subexpression elimination for CaseWhen statements. #30245 added support for creating subexpressions that are present in all branches of conditional statements. However, for a statement to be in "all branches" of a CaseWhen statement, it must also be in the elseValue. ### Why are the changes needed? Fix a bug where a subexpression can be created and run for branches of a conditional that don't pass. This can cause issues especially with a UDF in a branch that gets executed assuming the condition is true. ### Does this PR introduce _any_ user-facing change? Yes, fixes a potential bug where a UDF could be eagerly executed even though it might expect to have already passed some form of validation. For example: ``` val col = when($"id" < 0, myUdf($"id")) spark.range(1).select(when(col > 0, col)).show() ``` `myUdf($"id")` is considered a subexpression and eagerly evaluated, because it is pulled out as a common expression from both executions of the when clause, but if `id >= 0` it should never actually be run. ### How was this patch tested? Updated existing test with new case. Closes #32651 from Kimahriman/bug-case-subexpr-elimination-3.1. Authored-by: Adam Binford <adamq43@gmail.com> Signed-off-by: Liang-Chi Hsieh <viirya@gmail.com>
flyrain
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Sep 21, 2021
… values if elseValue is set ### What changes were proposed in this pull request? This PR fixes a bug with subexpression elimination for CaseWhen statements. apache#30245 added support for creating subexpressions that are present in all branches of conditional statements. However, for a statement to be in "all branches" of a CaseWhen statement, it must also be in the elseValue. ### Why are the changes needed? Fix a bug where a subexpression can be created and run for branches of a conditional that don't pass. This can cause issues especially with a UDF in a branch that gets executed assuming the condition is true. ### Does this PR introduce _any_ user-facing change? Yes, fixes a potential bug where a UDF could be eagerly executed even though it might expect to have already passed some form of validation. For example: ``` val col = when($"id" < 0, myUdf($"id")) spark.range(1).select(when(col > 0, col)).show() ``` `myUdf($"id")` is considered a subexpression and eagerly evaluated, because it is pulled out as a common expression from both executions of the when clause, but if `id >= 0` it should never actually be run. ### How was this patch tested? Updated existing test with new case. Closes apache#32651 from Kimahriman/bug-case-subexpr-elimination-3.1. Authored-by: Adam Binford <adamq43@gmail.com> Signed-off-by: Liang-Chi Hsieh <viirya@gmail.com>
fishcus
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Jan 12, 2022
… values if elseValue is set ### What changes were proposed in this pull request? This PR fixes a bug with subexpression elimination for CaseWhen statements. apache#30245 added support for creating subexpressions that are present in all branches of conditional statements. However, for a statement to be in "all branches" of a CaseWhen statement, it must also be in the elseValue. ### Why are the changes needed? Fix a bug where a subexpression can be created and run for branches of a conditional that don't pass. This can cause issues especially with a UDF in a branch that gets executed assuming the condition is true. ### Does this PR introduce _any_ user-facing change? Yes, fixes a potential bug where a UDF could be eagerly executed even though it might expect to have already passed some form of validation. For example: ``` val col = when($"id" < 0, myUdf($"id")) spark.range(1).select(when(col > 0, col)).show() ``` `myUdf($"id")` is considered a subexpression and eagerly evaluated, because it is pulled out as a common expression from both executions of the when clause, but if `id >= 0` it should never actually be run. ### How was this patch tested? Updated existing test with new case. Closes apache#32651 from Kimahriman/bug-case-subexpr-elimination-3.1. Authored-by: Adam Binford <adamq43@gmail.com> Signed-off-by: Liang-Chi Hsieh <viirya@gmail.com>
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What changes were proposed in this pull request?
This PR fixes a bug with subexpression elimination for CaseWhen statements. #30245 added support for creating subexpressions that are present in all branches of conditional statements. However, for a statement to be in "all branches" of a CaseWhen statement, it must also be in the elseValue.
Why are the changes needed?
Fix a bug where a subexpression can be created and run for branches of a conditional that don't pass. This can cause issues especially with a UDF in a branch that gets executed assuming the condition is true.
Does this PR introduce any user-facing change?
Yes, fixes a potential bug where a UDF could be eagerly executed even though it might expect to have already passed some form of validation. For example:
myUdf($"id")is considered a subexpression and eagerly evaluated, because it is pulled out as a common expression from both executions of the when clause, but ifid >= 0it should never actually be run.How was this patch tested?
Updated existing test with new case.