[GitHub] [spark] cloud-fan commented on a change in pull request #30975: [SPARK-33938][SQL] Optimize Like Any/All by LikeSimplification

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

cloud-fan commented on a change in pull request #30975:
URL: https://github.com/apache/spark/pull/30975#discussion_r551156002



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File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/expressions.scala
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@@ -634,36 +636,70 @@ object LikeSimplification extends Rule[LogicalPlan] {
   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.
+      None
+    } else {
+      pattern match {
+        case startsWith(prefix) =>
+          Some(StartsWith(input, Literal(prefix)))
+        case endsWith(postfix) =>
+          Some(EndsWith(input, Literal(postfix)))
+        // 'a%a' pattern is basically same with 'a%' && '%a'.
+        // However, the additional `Length` condition is required to prevent 'a' match 'a%a'.
+        case startsAndEndsWith(prefix, postfix) =>
+          Some(And(GreaterThanOrEqual(Length(input), Literal(prefix.length + postfix.length)),
+            And(StartsWith(input, Literal(prefix)), EndsWith(input, Literal(postfix)))))
+        case contains(infix) =>
+          Some(Contains(input, Literal(infix)))
+        case equalTo(str) =>
+          Some(EqualTo(input, Literal(str)))
+        case _ => None
+      }
+    }
+  }
+
+  private def simplifyMultiLike(
+      child: Expression, patterns: Seq[UTF8String], multi: MultiLikeBase): Expression = {
+    val (remainPatterns, replacements) = patterns.map { p =>
+      simplifyLike(child, p.toString).getOrElse(p)

Review comment:
       Let's not mix `Expression` and `UTF8String`




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