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https://issues.apache.org/jira/browse/SPARK-24402?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Xiao Li resolved SPARK-24402.
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Resolution: Fixed
Fix Version/s: 2.4.0
> Optimize `In` expression when only one element in the collection or
> collection is empty
> ----------------------------------------------------------------------------------------
>
> Key: SPARK-24402
> URL: https://issues.apache.org/jira/browse/SPARK-24402
> Project: Spark
> Issue Type: New Feature
> Components: SQL
> Affects Versions: 2.3.0
> Reporter: DB Tsai
> Assignee: DB Tsai
> Priority: Major
> Fix For: 2.4.0
>
>
> Two new rules in the logical plan optimizers are added.
> # When there is only one element in the *{{Collection}}*, the physical plan
> will be optimized to *{{EqualTo}}*, so predicate pushdown can be used.
> {code}
> profileDF.filter( $"profileID".isInCollection(Set(6))).explain(true)
> """
> |== Physical Plan ==|
> |*(1) Project [profileID#0|#0]|
> |+- *(1) Filter (isnotnull(profileID#0) && (profileID#0 = 6))|
> |+- *(1) FileScan parquet [profileID#0|#0] Batched: true, Format: Parquet,|
> |PartitionFilters: [],|
> |PushedFilters: [IsNotNull(profileID), EqualTo(profileID,6)],|
> |ReadSchema: struct<profileID:int>
> """.stripMargin
> {code}
> # When the *{{Set}}* is empty, and the input is nullable, the logical
> plan will be simplified to
> {code}
> profileDF.filter( $"profileID".isInCollection(Set())).explain(true)
> """
> |== Optimized Logical Plan ==|
> |Filter if (isnull(profileID#0)) null else false|
> |+- Relation[profileID#0|#0] parquet
> """.stripMargin
> {code}
> TODO:
> # For multiple conditions with numbers less than certain thresholds,
> we should still allow predicate pushdown.
> # Optimize the `In` using tableswitch or lookupswitch when the
> numbers of the categories are low, and they are `Int`, `Long`.
> # The default immutable hash trees set is slow for query, and we
> should do benchmark for using different set implementation for faster
> query.
> # `filter(if (condition) null else false)` can be optimized to false.
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