[GitHub] [spark] maropu commented on a change in pull request #31477: [SPARK-34369][SQL][WEBUI] Track number of pairs processed out of Join.

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

maropu commented on a change in pull request #31477:
URL: https://github.com/apache/spark/pull/31477#discussion_r570624874



##########
File path: sql/core/src/main/scala/org/apache/spark/sql/execution/joins/BroadcastHashJoinExec.scala
##########
@@ -57,7 +57,8 @@ case class BroadcastHashJoinExec(
   }
 
   override lazy val metrics = Map(
-    "numOutputRows" -> SQLMetrics.createMetric(sparkContext, "number of output rows"))
+    "numOutputRows" -> SQLMetrics.createMetric(sparkContext, "number of output rows"),
+    "numMatchedPairs" -> SQLMetrics.createMetric(sparkContext, "number of matched pairs"))

Review comment:
       `numMatchedPairs` -> `numJoinedRows`?

##########
File path: sql/core/src/main/scala/org/apache/spark/sql/execution/joins/HashJoin.scala
##########
@@ -415,24 +431,26 @@ trait HashJoin extends BaseJoinExec with CodegenSupport {
       ctx: CodegenContext,
       input: Seq[ExprCode]): (String, String, Seq[ExprCode]) = {
     val matched = ctx.freshName("matched")
+    val numMatched = metricTerm(ctx, "numMatchedPairs")
     val buildVars = genBuildSideVars(ctx, matched)
-    val checkCondition = if (condition.isDefined) {
-      val expr = condition.get
-      // evaluate the variables from build side that used by condition
-      val eval = evaluateRequiredVariables(buildPlan.output, buildVars, expr.references)
-      // filter the output via condition
-      ctx.currentVars = input ++ buildVars
-      val ev =
-        BindReferences.bindReference(expr, streamedPlan.output ++ buildPlan.output).genCode(ctx)
-      val skipRow = s"${ev.isNull} || !${ev.value}"
-      s"""
-         |$eval
-         |${ev.code}
-         |if (!($skipRow))
-       """.stripMargin
-    } else {
-      ""
-    }
+    val checkCondition = s"$numMatched.add(1);\n" +
+      (if (condition.isDefined) {
+        val expr = condition.get
+        // evaluate the variables from build side that used by condition
+        val eval = evaluateRequiredVariables(buildPlan.output, buildVars, expr.references)
+        // filter the output via condition
+        ctx.currentVars = input ++ buildVars
+        val ev =
+          BindReferences.bindReference(expr, streamedPlan.output ++ buildPlan.output).genCode(ctx)
+        val skipRow = s"${ev.isNull} || !${ev.value}"
+        s"""
+           |$eval
+           |${ev.code}
+           |if (!($skipRow))
+         """.stripMargin
+      } else {
+        ""
+      })

Review comment:
       Could you avoid unnecessary changes? For example;
   ```
       val checkCondition = if (condition.isDefined) {
         val expr = condition.get
         ...
       } else {
           ""
       }
       val some_val = s"$numMatched.add(1);\n$checkCondition"
       (matched, some_val, buildVars)
   ```

##########
File path: sql/core/src/main/scala/org/apache/spark/sql/execution/joins/BroadcastNestedLoopJoinExec.scala
##########
@@ -89,13 +90,20 @@ case class BroadcastNestedLoopJoinExec(
     }
   }
 
-  @transient private lazy val boundCondition = {
+  private val numMatchedPairs = longMetric("numMatchedPairs")
+
+  @transient private lazy val boundCondition: InternalRow => Boolean =
     if (condition.isDefined) {

Review comment:
       If `condition` is empty, `numOutputRows` == `numMatchedPairs `? If so, could we only show this new metric in the web UI when `condition` defined?




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