beliefer commented on a change in pull request #30975:
URL: https://github.com/apache/spark/pull/30975#discussion_r553151297
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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 +635,68 @@ 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 (remainPatternMap, replacementMap) =
+ patterns.map { p => p -> simplifyLike(child,
p.toString)}.partition(_._2.isEmpty)
+ val remainPatterns = remainPatternMap.map(_._1)
+ val replacements = replacementMap.map(_._2.get)
+ if (replacements.isEmpty) {
+ multi
+ } else {
+ multi match {
+ case l: LikeAll => And(replacements.reduceLeft(And), l.copy(patterns =
remainPatterns))
Review comment:
For example, patterns a, b, c, d, e, and f. Suppose a, b, c, and d are
patterns that can be optimized with startsWith. According to the current logic,
it is startsWith(a)&startsWith(b)&startsWith(c)&startsWith(d)&LikeAll(e,f).
Their hierarchy is not shown here.
We can use the threshold to determine the number of patterns that can be
optimized, for example, only two patterns can be optimized. Then it is
startsWith(a)&startsWith(b)&LikeAll(c,d,e,f)
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