[SPARK-30759] The cache in StringRegexExpression is not initialized for foldable patterns - ASF JIRA

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Details

Type: Bug
Status: Resolved
Priority: Minor
Resolution: Fixed
Affects Version/s: 1.6.3, 2.0.2, 2.1.3, 2.2.3, 2.3.4, 2.4.5
Fix Version/s: 2.4.6, 3.0.0
Component/s: SQL
Labels:
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Description

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:

SELECT '%SystemDrive%\Users\John' _FUNC_ '%SystemDrive%\\Users.*';

the code https://github.com/apache/spark/blob/8aebc80e0e67bcb1aa300b8c8b1a209159237632/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/regexpExpressions.scala#L45-L48:

  // try cache the pattern for Literal
  private lazy val cache: Pattern = pattern match {
    case Literal(value: String, StringType) => compile(value)
    case _ => null
  }

The attached screenshot shows that foldable expression doesn't fall to the first case.