Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/10762#discussion_r51832603
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala
---
@@ -1159,6 +1161,47 @@ class Analyzer(
}
}
}
+
+ /**
+ * Removes natural joins by calculating output columns based on output
from two sides,
+ * Then apply a Project on a normal Join to eliminate natural join.
+ */
+ object ResolveNaturalJoin extends Rule[LogicalPlan] {
+ override def apply(plan: LogicalPlan): LogicalPlan = plan
resolveOperators {
+ // Should not skip unresolved nodes because natural join is always
unresolved.
+ case j @ Join(left, right, NaturalJoin(joinType), condition) if
j.resolvedExceptNatural =>
+ // find common column names from both sides, should be treated
like usingColumns
+ val joinNames =
left.output.map(_.name).intersect(right.output.map(_.name))
+ val leftKeys = joinNames.map(keyName => left.output.find(_.name ==
keyName).get)
+ val rightKeys = joinNames.map(keyName => right.output.find(_.name
== keyName).get)
+ val joinPairs = leftKeys.zip(rightKeys)
+ // Add joinPairs to joinConditions
+ val newCondition = (condition ++ joinPairs.map {
+ case (l, r) => EqualTo(l, r)
+ }).reduceLeftOption(And)
+ // columns not in joinPairs
+ val lUniqueOutput = left.output.filterNot(att =>
leftKeys.contains(att))
+ val rUniqueOutput = right.output.filterNot(att =>
rightKeys.contains(att))
+ // we should only keep unique columns(depends on joinType) for
joinCols
+ val projectList = joinType match {
+ case LeftOuter =>
+ leftKeys ++ lUniqueOutput ++
rUniqueOutput.map(_.withNullability(true))
--- End diff --
nvm i figured it out.
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