Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/13494#discussion_r68377009
--- Diff:
sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveMetastoreCatalog.scala ---
@@ -457,6 +458,125 @@ private[hive] class
HiveMetastoreCatalog(sparkSession: SparkSession) extends Log
allowExisting)
}
}
+
+ /**
+ * When scanning only partition columns, get results based on metadata
without scanning files.
+ * It is used for distinct or distinct/Max/Min aggregations, example:
max(partition).
+ */
+ object MetadataOnlyOptimizer extends Rule[LogicalPlan] {
+
+ private def canSupportMetadataOnly(a: Aggregate): Boolean = {
+ val aggregateExpressions = a.aggregateExpressions.flatMap { expr =>
+ expr.collect {
+ case agg: AggregateExpression => agg
+ }
+ }.distinct
+ aggregateExpressions.forall { agg =>
+ if (agg.isDistinct) {
+ true
+ } else {
+ agg.aggregateFunction match {
+ case max: Max => true
+ case min: Min => true
+ case _ => false
+ }
+ }
+ }
+ }
+
+ private def findRelation(plan: LogicalPlan): (Option[LogicalPlan],
Seq[Expression]) = {
+ plan match {
+ case relation @ LogicalRelation(files: HadoopFsRelation, _, table)
+ if files.partitionSchema.nonEmpty =>
+ (Some(relation), Seq.empty[Expression])
+
+ case relation: MetastoreRelation if
relation.partitionKeys.nonEmpty =>
+ (Some(relation), Seq.empty[Expression])
+
+ case p @ Project(_, child) =>
--- End diff --
is it safe to keep traversing the plan tree through `Project`?
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