cloud-fan commented on code in PR #50921:
URL: https://github.com/apache/spark/pull/50921#discussion_r2184500117
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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 +123,103 @@ case class JDBCScanBuilder(
}
}
+ override def isOtherSideCompatibleForJoin(other: SupportsPushDownJoin):
Boolean = {
+ other.isInstanceOf[JDBCScanBuilder] &&
+ jdbcOptions.url == other.asInstanceOf[JDBCScanBuilder].jdbcOptions.url
+ };
+
+ // When getJoinedSchema is called, schema shouldn't be pruned yet because
pushDownJoin API call
+ // can fail. For this reason, we are temporarily holding pruned schema in
new variable that is
+ // later used in pushDownJoin when crafting the SQL query.
+ var aboutToBePrunedSchema: StructType = finalSchema
+
+ override def getJoinedSchema(
+ other: SupportsPushDownJoin,
+ requiredSchema: StructType,
+ otherSideRequiredSchema: StructType): StructType = {
+ aboutToBePrunedSchema = requiredSchema
+ other.asInstanceOf[JDBCScanBuilder].aboutToBePrunedSchema =
otherSideRequiredSchema
+
+ var joinedSchema = StructType(Seq())
+
+ (requiredSchema.fields ++ otherSideRequiredSchema.fields)
+ .zipWithIndex
+ .foreach { case (field, idx) =>
+ val newFieldName = JoinOutputAliasIterator.generateColumnAlias
+ joinedSchema =
+ joinedSchema.add(newFieldName, field.dataType, field.nullable,
field.metadata)
+ }
+
+ joinedSchema
+ }
+
+ override def pushDownJoin(
+ other: SupportsPushDownJoin,
+ requiredSchema: StructType,
+ joinType: JoinType,
+ condition: Predicate): Boolean = {
+ if (!jdbcOptions.pushDownJoin || !dialect.supportsJoin) return false
+ val otherJdbcScanBuilder = other.asInstanceOf[JDBCScanBuilder]
+
+ val requiredOutput =
requiredSchema.fields.take(aboutToBePrunedSchema.length).map(_.name)
+ val otherSideRequiredOutput =
+ requiredSchema.fields.drop(aboutToBePrunedSchema.length).map(_.name)
+
+ val sqlQuery = buildSQLQueryUsedInJoinPushDown(requiredOutput)
+ val otherSideSqlQuery = otherJdbcScanBuilder
+ .buildSQLQueryUsedInJoinPushDown(otherSideRequiredOutput)
+
+ val joinOutputColumnsString =
+ requiredSchema.fields.map(f =>
dialect.quoteIdentifier(f.name)).mkString(",")
+
+ val joinTypeString = joinType match {
+ case JoinType.INNER_JOIN => "INNER JOIN"
+ case _ => ""
+ }
+
+ if (joinTypeString.isEmpty) return false
+
+ val compiledCondition = dialect.compileExpression(condition)
+ if (!compiledCondition.isDefined) return false
+
+ val conditionString = compiledCondition.get
+
+ val joinQuery = s"""
+ |SELECT $joinOutputColumnsString FROM
+ |($sqlQuery) ${JoinOutputAliasIterator.generateSubqueryQualifier}
Review Comment:
does the subquery alias matter here given the column names won't have
conflict? Can we also use `t1` and `t2`?
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