cloud-fan commented on code in PR #50921:
URL: https://github.com/apache/spark/pull/50921#discussion_r2108703627
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sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/v2/jdbc/JDBCScanBuilder.scala:
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@@ -121,6 +126,128 @@ case class JDBCScanBuilder(
}
}
+ override def isRightSideCompatibleForJoin(other: SupportsPushDownJoin):
Boolean = {
+ other.isInstanceOf[JDBCScanBuilder] &&
+ jdbcOptions.url == other.asInstanceOf[JDBCScanBuilder].jdbcOptions.url
+ };
+
+ override def pushJoin(
+ other: SupportsPushDownJoin,
+ joinType: JoinType,
+ condition: Optional[Predicate],
+ leftRequiredSchema: StructType,
+ rightRequiredSchema: StructType
+ ): Boolean = {
+ if (!jdbcOptions.pushDownJoin || !dialect.supportsJoin) return false
+
+ val leftNodeSQLQuery = buildSQLQuery()
+ val rightNodeSQLQuery = other.asInstanceOf[JDBCScanBuilder].buildSQLQuery()
+
+ val leftSideQualifier = JoinOutputAliasIterator.get
+ val rightSideQualifier = JoinOutputAliasIterator.get
+
+ val leftProjections: Seq[JoinColumn] = leftRequiredSchema.fields.map { e =>
+ new JoinColumn(Array(leftSideQualifier), e.name, true)
+ }.toSeq
+ val rightProjections: Seq[JoinColumn] = rightRequiredSchema.fields.map { e
=>
+ new JoinColumn(Array(rightSideQualifier), e.name, false)
+ }.toSeq
+
+ var aliasedLeftSchema = StructType(Seq())
+ var aliasedRightSchema = StructType(Seq())
+ val outputAliasPrefix = JoinOutputAliasIterator.get
+
+ val aliasedOutput = (leftProjections ++ rightProjections)
+ .zipWithIndex
+ .map { case (proj, i) =>
+ val name = s"${outputAliasPrefix}_col_$i"
+ val output = FieldReference(name)
+ if (i < leftProjections.length) {
+ val field = leftRequiredSchema.fields(i)
+ aliasedLeftSchema =
+ aliasedLeftSchema.add(name, field.dataType, field.nullable,
field.metadata)
+ } else {
+ val field = rightRequiredSchema.fields(i -
leftRequiredSchema.fields.length)
+ aliasedRightSchema =
+ aliasedRightSchema.add(name, field.dataType, field.nullable,
field.metadata)
+ }
+
+ s"""${dialect.compileExpression(proj).get} AS
${dialect.compileExpression(output).get}"""
+ }.mkString(",")
+
+ val compiledJoinType = dialect.compileJoinType(joinType)
+ if (!compiledJoinType.isDefined) return false
+
+ val conditionString = condition.toScala match {
+ case Some(cond) =>
+ qualifyCondition(cond, leftSideQualifier, rightSideQualifier)
+ s"ON ${dialect.compileExpression(cond).get}"
Review Comment:
I think it's safer to pass the generated subquery aliases to the
`compileExpression` function (or add a new `compileJoinCondition` function),
which should respect the aliases when generating SQL for JoinColumn. It's
better than making `JoinColumn` mutable.
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