From 3d7f201f2adc2d33be6f564fa76435c18552f4ba Mon Sep 17 00:00:00 2001
From: Wenchen Fan <wenchen@databricks.com>
Date: Mon, 10 Apr 2017 13:36:08 +0800
Subject: [SPARK-20229][SQL] add semanticHash to QueryPlan

## What changes were proposed in this pull request?

Like `Expression`, `QueryPlan` should also have a `semanticHash` method, then we can put plans to a hash map and look it up fast. This PR refactors `QueryPlan` to follow `Expression` and put all the normalization logic in `QueryPlan.canonicalized`, so that it's very natural to implement `semanticHash`.

follow-up: improve `CacheManager` to leverage this `semanticHash` and speed up plan lookup, instead of iterating all cached plans.

## How was this patch tested?

existing tests. Note that we don't need to test the `semanticHash` method, once the existing tests prove `sameResult` is correct, we are good.

Author: Wenchen Fan <wenchen@databricks.com>

Closes #17541 from cloud-fan/plan-semantic.
---
 .../sql/hive/execution/HiveTableScanExec.scala     | 45 ++++++++++------------
 1 file changed, 21 insertions(+), 24 deletions(-)

(limited to 'sql/hive')

diff --git a/sql/hive/src/main/scala/org/apache/spark/sql/hive/execution/HiveTableScanExec.scala b/sql/hive/src/main/scala/org/apache/spark/sql/hive/execution/HiveTableScanExec.scala
index 28f074849c..fab0d7fa84 100644
--- a/sql/hive/src/main/scala/org/apache/spark/sql/hive/execution/HiveTableScanExec.scala
+++ b/sql/hive/src/main/scala/org/apache/spark/sql/hive/execution/HiveTableScanExec.scala
@@ -72,7 +72,7 @@ case class HiveTableScanExec(
 
   // Bind all partition key attribute references in the partition pruning predicate for later
   // evaluation.
-  private val boundPruningPred = partitionPruningPred.reduceLeftOption(And).map { pred =>
+  private lazy val boundPruningPred = partitionPruningPred.reduceLeftOption(And).map { pred =>
     require(
       pred.dataType == BooleanType,
       s"Data type of predicate $pred must be BooleanType rather than ${pred.dataType}.")
@@ -80,20 +80,22 @@ case class HiveTableScanExec(
     BindReferences.bindReference(pred, relation.partitionCols)
   }
 
-  // Create a local copy of hadoopConf,so that scan specific modifications should not impact
-  // other queries
-  @transient private val hadoopConf = sparkSession.sessionState.newHadoopConf()
-
-  @transient private val hiveQlTable = HiveClientImpl.toHiveTable(relation.tableMeta)
-  @transient private val tableDesc = new TableDesc(
+  @transient private lazy val hiveQlTable = HiveClientImpl.toHiveTable(relation.tableMeta)
+  @transient private lazy val tableDesc = new TableDesc(
     hiveQlTable.getInputFormatClass,
     hiveQlTable.getOutputFormatClass,
     hiveQlTable.getMetadata)
 
-  // append columns ids and names before broadcast
-  addColumnMetadataToConf(hadoopConf)
+  // Create a local copy of hadoopConf,so that scan specific modifications should not impact
+  // other queries
+  @transient private lazy val hadoopConf = {
+    val c = sparkSession.sessionState.newHadoopConf()
+    // append columns ids and names before broadcast
+    addColumnMetadataToConf(c)
+    c
+  }
 
-  @transient private val hadoopReader = new HadoopTableReader(
+  @transient private lazy val hadoopReader = new HadoopTableReader(
     output,
     relation.partitionCols,
     tableDesc,
@@ -104,7 +106,7 @@ case class HiveTableScanExec(
     Cast(Literal(value), dataType).eval(null)
   }
 
-  private def addColumnMetadataToConf(hiveConf: Configuration) {
+  private def addColumnMetadataToConf(hiveConf: Configuration): Unit = {
     // Specifies needed column IDs for those non-partitioning columns.
     val columnOrdinals = AttributeMap(relation.dataCols.zipWithIndex)
     val neededColumnIDs = output.flatMap(columnOrdinals.get).map(o => o: Integer)
@@ -198,18 +200,13 @@ case class HiveTableScanExec(
     }
   }
 
-  override def sameResult(plan: SparkPlan): Boolean = plan match {
-    case other: HiveTableScanExec =>
-      val thisPredicates = partitionPruningPred.map(cleanExpression)
-      val otherPredicates = other.partitionPruningPred.map(cleanExpression)
-
-      val result = relation.sameResult(other.relation) &&
-        output.length == other.output.length &&
-          output.zip(other.output)
-            .forall(p => p._1.name == p._2.name && p._1.dataType == p._2.dataType) &&
-              thisPredicates.length == otherPredicates.length &&
-                thisPredicates.zip(otherPredicates).forall(p => p._1.semanticEquals(p._2))
-      result
-    case _ => false
+  override lazy val canonicalized: HiveTableScanExec = {
+    val input: AttributeSeq = relation.output
+    HiveTableScanExec(
+      requestedAttributes.map(normalizeExprId(_, input)),
+      relation.canonicalized.asInstanceOf[CatalogRelation],
+      partitionPruningPred.map(normalizeExprId(_, input)))(sparkSession)
   }
+
+  override def otherCopyArgs: Seq[AnyRef] = Seq(sparkSession)
 }
-- 
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