hsyuan commented on a change in pull request #1157: [CALCITE-2969] Improve
design of join-like relational expressions
URL: https://github.com/apache/calcite/pull/1157#discussion_r279157499
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File path: core/src/main/java/org/apache/calcite/rel/core/Join.java
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@@ -230,6 +237,17 @@ public boolean isSemiJoinDone() {
return false;
}
+ /**
+ * Returns whether this LogicalJoin is a semi-join but does
+ * not comes from decorrelate.
+ *
+ * @return true if this is semi but without correlate variables.
+ */
+ public boolean isNonCorrelateSemiJoin() {
+ return (this.variablesSet == null || this.variablesSet.size() == 0)
+ && joinType == JoinRelType.SEMI;
+ }
Review comment:
@danny0405 The purpose of transforming a correlate to a join is getting rid
of Variables.
@zabetak It is in RelDecorrelator, which is not rule based, sadly. Some
SubqueryRemoveRule will transform subquery into Correlate, some
SubqueryRemoveRule will directly transform subquery into a Join. :(
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