[GitHub] [spark] cloud-fan commented on a change in pull request #35465: [SPARK-38168][SQL] LikeSimplification rule handles escape characters

[GitBox <gi...@apache.org>]

cloud-fan commented on a change in pull request #35465:
URL: https://github.com/apache/spark/pull/35465#discussion_r803309117



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File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/expressions.scala
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@@ -680,42 +680,50 @@ object PushFoldableIntoBranches extends Rule[LogicalPlan] with PredicateHelper {
  * pattern.
  */
 object LikeSimplification extends Rule[LogicalPlan] {
-  // if guards below protect from escapes on trailing %.
-  // Cases like "something\%" are not optimized, but this does not affect correctness.
-  private val startsWith = "([^_%]+)%".r
-  private val endsWith = "%([^_%]+)".r
-  private val startsAndEndsWith = "([^_%]+)%([^_%]+)".r
-  private val contains = "%([^_%]+)%".r
-  private val equalTo = "([^_%]*)".r
-
   private def simplifyLike(
       input: Expression, pattern: String, escapeChar: Char = '\\'): Option[Expression] = {
-    if (pattern.contains(escapeChar)) {
-      // There are three different situations when pattern containing escapeChar:
-      // 1. pattern contains invalid escape sequence, e.g. 'm\aca'
-      // 2. pattern contains escaped wildcard character, e.g. 'ma\%ca'
-      // 3. pattern contains escaped escape character, e.g. 'ma\\ca'
-      // Although there are patterns can be optimized if we handle the escape first, we just
-      // skip this rule if pattern contains any escapeChar for simplicity.

Review comment:
       This is a trade-off between code simplicity and performance. The assumption is that using escape char is rare and we shouldn't add a complicated implementation for it.
   
   Besides, Spark now provides `starts_with`, `ends_with`, etc. functions and people can use them directly.




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