spark-reviews mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From GitBox <...@apache.org>
Subject [GitHub] [spark] beliefer commented on a change in pull request #27058: [SPARK-30395][SQL] When one or more DISTINCT aggregate expressions operate on the same field, the DISTINCT aggregate expression allows the use of the FILTER clause
Date Thu, 09 Jan 2020 03:24:56 GMT
beliefer commented on a change in pull request #27058: [SPARK-30395][SQL] When one or more
DISTINCT aggregate expressions operate on the same field, the DISTINCT aggregate expression
allows the use of the FILTER clause
URL: https://github.com/apache/spark/pull/27058#discussion_r364544828
 
 

 ##########
 File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/RewriteDistinctAggregates.scala
 ##########
 @@ -317,7 +363,74 @@ object RewriteDistinctAggregates extends Rule[LogicalPlan] {
       }
       Aggregate(groupByAttrs, patchedAggExpressions, firstAggregate)
     } else {
-      a
+      val (distinctAggExpressions, regularAggExpressions) = aggExpressions.partition(_.isDistinct)
+      if (distinctAggExpressions.exists(_.filter.isDefined)) {
+        val regularAggExprs = regularAggExpressions.filter(e => e.children.exists(!_.foldable))
+        val regularFunChildren = regularAggExprs
+          .flatMap(_.aggregateFunction.children.filter(!_.foldable))
+        val regularFilterAttrs = regularAggExprs.flatMap(_.filterAttributes)
+        val regularAggChildren = (regularFunChildren ++ regularFilterAttrs).distinct
+        val regularAggChildAttrMap = regularAggChildren.map(expressionAttributePair)
+        val regularAggChildAttrLookup = regularAggChildAttrMap.toMap
+        val regularOperatorMap = regularAggExprs.map {
+          case ae @ AggregateExpression(af, _, _, filter, _) =>
+            val newChildren = af.children.map(c => regularAggChildAttrLookup.getOrElse(c,
c))
+            val raf = af.withNewChildren(newChildren).asInstanceOf[AggregateFunction]
+            val filterOpt = filter.map(_.transform {
+              case a: Attribute => regularAggChildAttrLookup.getOrElse(a, a)
+            })
+            val aggExpr = ae.copy(aggregateFunction = raf, filter = filterOpt)
+            (ae, aggExpr)
+        }
+        val distinctAggExprs = distinctAggExpressions.filter(e => e.children.exists(!_.foldable))
+        val rewriteDistinctOperatorMap = distinctAggExprs.zipWithIndex.map {
+          case (ae @ AggregateExpression(af, _, _, filter, _), i) =>
+            val phantomId = i + 1
 
 Review comment:
               // Why do we need to construct the phantom id ?
               // First, In order to reduce costs, it is better to handle the filter clause
locally.
               // e.g. COUNT (DISTINCT a) FILTER (WHERE id > 1), evaluate expression
               // If(id > 1) 'a else null first, and use the result as output.
               // Second, If more than one DISTINCT aggregate expression uses the same column,
               // We need to construct the phantom attributes so as the output not lost.
               // e.g. SUM (DISTINCT a), COUNT (DISTINCT a) FILTER (WHERE id > 1) will
output
               // attribute 'a and attribute 'phantom1-a instead of two 'a.
               // Note: We just need to illusion the expression with filter clause.

----------------------------------------------------------------
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
 
For queries about this service, please contact Infrastructure at:
users@infra.apache.org


With regards,
Apache Git Services

---------------------------------------------------------------------
To unsubscribe, e-mail: reviews-unsubscribe@spark.apache.org
For additional commands, e-mail: reviews-help@spark.apache.org


Mime
View raw message