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https://issues.apache.org/jira/browse/SPARK-30759?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17033889#comment-17033889
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Dongjoon Hyun commented on SPARK-30759:
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Hi, [~maxgekk]. As you wrote on the PR, this is a behavior since 1.0.0. So, I
convert this into an improvement JIRA. That will be easier to understand this
issue impact and contribution.
> The cache in StringRegexExpression is not initialized for foldable patterns
> ---------------------------------------------------------------------------
>
> Key: SPARK-30759
> URL: https://issues.apache.org/jira/browse/SPARK-30759
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 3.1.0
> Reporter: Maxim Gekk
> Priority: Minor
> Attachments: Screen Shot 2020-02-08 at 22.45.50.png
>
>
> In the case of foldable patterns, the cache in StringRegexExpression should
> be evaluated once but in fact it is compiled every time. Here is the example:
> {code:sql}
> SELECT '%SystemDrive%\Users\John' _FUNC_ '%SystemDrive%\\Users.*';
> {code}
> the code
> https://github.com/apache/spark/blob/8aebc80e0e67bcb1aa300b8c8b1a209159237632/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/regexpExpressions.scala#L45-L48:
> {code:scala}
> // try cache the pattern for Literal
> private lazy val cache: Pattern = pattern match {
> case Literal(value: String, StringType) => compile(value)
> case _ => null
> }
> {code}
> The attached screenshot shows that foldable expression doesn't fall to the
> first case.
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