[SPARK-27739][SQL] df.persist should save stats from optimized plan

Author: jzhuge

sql/core/src/main/scala/org/apache/spark/sql/execution/CacheManager.scala

@@ -79,12 +79,13 @@ class CacheManager extends Logging {
       logWarning("Asked to cache already cached data.")
     } else {
       val sparkSession = query.sparkSession
+      val qe = sparkSession.sessionState.executePlan(planToCache)
       val inMemoryRelation = InMemoryRelation(
         sparkSession.sessionState.conf.useCompression,
         sparkSession.sessionState.conf.columnBatchSize, storageLevel,
-        sparkSession.sessionState.executePlan(planToCache).executedPlan,
+        qe.executedPlan,
         tableName,
-        planToCache)
+        qe.optimizedPlan)
       this.synchronized {
         if (lookupCachedData(planToCache).nonEmpty) {
           logWarning("Data has already been cached.")