[GitHub] [spark] gatorsmile commented on a change in pull request #24580: [SPARK-27674][SQL] the hint should not be dropped after cache lookup

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

gatorsmile commented on a change in pull request #24580: [SPARK-27674][SQL] the hint should not be dropped after cache lookup
URL: https://github.com/apache/spark/pull/24580#discussion_r283189552
 
 

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 File path: sql/core/src/main/scala/org/apache/spark/sql/execution/CacheManager.scala
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 @@ -212,17 +213,18 @@ class CacheManager extends Logging {
   def useCachedData(plan: LogicalPlan): LogicalPlan = {
     val newPlan = plan transformDown {
       case command: IgnoreCachedData => command
-      // Do not lookup the cache by hint node. Hint node is special, we should ignore it when
-      // canonicalizing plans, so that plans which are same except hint can hit the same cache.
-      // However, we also want to keep the hint info after cache lookup. Here we skip the hint
-      // node, so that the returned caching plan won't replace the hint node and drop the hint info
-      // from the original plan.
-      case hint: ResolvedHint => hint
 
       case currentFragment =>
-        lookupCachedData(currentFragment)
-          .map(_.cachedRepresentation.withOutput(currentFragment.output))
-          .getOrElse(currentFragment)
+        lookupCachedData(currentFragment).map { cached =>
+          // After cache lookup, we should still keep the hints from the input plan.
 
 Review comment:
   If the original cached plan has a hint, should we keep them? We need to define a clear behavior in our cache manager.

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