[GitHub] [spark] cloud-fan commented on a change in pull request #30625: [SPARK-33677][SQL] Skip LikeSimplification rule if pattern contains any escapeChar

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cloud-fan commented on a change in pull request #30625:
URL: https://github.com/apache/spark/pull/30625#discussion_r537301594



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File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/expressions.scala
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@@ -543,27 +543,27 @@ object LikeSimplification extends Rule[LogicalPlan] {
   private val equalTo = "([^_%]*)".r
 
   def apply(plan: LogicalPlan): LogicalPlan = plan transformAllExpressions {
-    case Like(input, Literal(pattern, StringType), escapeChar) =>
+    case l @ Like(input, Literal(pattern, StringType), escapeChar) =>
       if (pattern == null) {
         // If pattern is null, return null value directly, since "col like null" == null.
         Literal(null, BooleanType)
       } else {
-        val escapeStr = String.valueOf(escapeChar)
         pattern.toString match {
-          case startsWith(prefix) if !prefix.endsWith(escapeStr) =>
+          case p if p.contains(escapeChar) => l

Review comment:
       correct me if I was wrong: we need to make sure this rule doesn't change result. If the pattern is invalid, `Like` should fail. However, it's expensive to validate the pattern (need to compile it). Here we use `p.contains(escapeChar)` as a shortcut to know if the pattern might be invalid.
   
   Can we add some comments to explain it?




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