rubenada 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_r283676253
##########
File path: core/src/main/java/org/apache/calcite/rel/core/Join.java
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@@ -230,6 +237,15 @@ public boolean isSemiJoinDone() {
return false;
}
+ /**
+ * Returns whether this Join is a semijoin.
+ *
+ * @return true if this is semi but without correlate variables.
+ */
+ public boolean isSemiJoin() {
Review comment:
@danny0405 I know it does not happen right now, but in the (near) future, we
will also have Join instances with type=ANTI, which also outputs one side; so
if we really need to add a new method, I'd propose it to have a more generic
name, e.g. moving the SemiJoinType#returnsJustFirstInput logic into here:
```
public boolean returnsJustFirstInput() {
switch (this) {
case SEMI:
case ANTI:
return true;
default:
return false;
}
}
```
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