Github user rxin commented on a diff in the pull request: https://github.com/apache/spark/pull/1325#discussion_r14640036 --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala --- @@ -112,6 +113,26 @@ object ColumnPruning extends Rule[LogicalPlan] { } /** + * Simplifies LIKE expressions that do not need full regular expressions to evaluate the condition. + * For example, when the expression is just checking to see if a string starts with a given + * pattern. + */ +object LikeSimplification extends Rule[LogicalPlan] { + val startsWith = "([^_%]+)%".r --- End diff -- Actually this sounds good (it's just not a case to optimize for). Can we add comment inline to explain that? i.e. "This doesn't match case like "abcd\\%", but it doesn't affect correctness."
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