julianhyde 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_r279473653
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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:
The reason for variablesSet is correlated scalar sub-query in the ON clause.
Similarly Filter needs variablesSet if there is a correlated scalar sub-query
in its condition, and Project needs variablesSet for correlated scalar
sub-query in one of the project expressions.
This stuff isn't very well tested, but it is needed because sub-query can
occur anywhere in a query.
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