[GitHub] [spark] maropu commented on a change in pull request #26875: [SPARK-30245][SQL] Add cache for Like and RLike when pattern is not static

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maropu commented on a change in pull request #26875: [SPARK-30245][SQL] Add cache for Like and RLike when pattern is not static
URL: https://github.com/apache/spark/pull/26875#discussion_r357489170
 
 

 ##########
 File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/regexpExpressions.scala
 ##########
 @@ -162,10 +160,17 @@ case class Like(left: Expression, right: Expression, escapeChar: Char = '\\')
       } else {
         escapeChar
       }
+      val rightStr = ctx.freshName("rightStr")
+      val pattern = ctx.addMutableState(patternClass, "pattern")
+      val lastRightStr = ctx.addMutableState(classOf[String].getName, "lastRightStr")
+
       nullSafeCodeGen(ctx, ev, (eval1, eval2) => {
         s"""
           String $rightStr = $eval2.toString();
-          $patternClass $pattern = $patternClass.compile($escapeFunc($rightStr, '$newEscapeChar'));
+          if ($lastRightStr != $rightStr) {
 
 Review comment:
   I think this optimization is a corner case and highly depends on input data.... cc: @dongjoon-hyun 

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