silundong commented on code in PR #4619:
URL: https://github.com/apache/calcite/pull/4619#discussion_r2587452372
##########
core/src/main/java/org/apache/calcite/rel/core/JoinRelType.java:
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@@ -91,7 +91,32 @@ public enum JoinRelType {
/**
* The left version of an ASOF join, where each row from the left table is
part of the output.
*/
- LEFT_ASOF;
+ LEFT_ASOF,
+
+ /**
+ * An MARK JOIN will keep all rows from the left side and creates a new
attribute to mark a
+ * tuple as having join partners from right side or not. Refer to
+ * <a href="https://dl.gi.de/items/c5f7c49f-1572-490e-976a-cc4292519bdd";>
+ * The Complete Story of Joins (in HyPer)</a>.
+ *
+ * <p>Example:
+ * <blockquote><pre>
+ * SELECT EMPNO FROM EMP
+ * WHERE EXISTS (SELECT 1 FROM DEPT
+ * WHERE DEPT.DEPTNO = EMP.DEPTNO)
+ * OR EMPNO > 1
+ *
+ * LogicalProject(EMPNO=[$0])
+ * LogicalFilter(condition=[OR($9, >($0, 1))])
+ * LogicalJoin(condition=[IS NOT DISTINCT FROM($7, $9)], joinType=[mark])
+ * LogicalTableScan(table=[[CATALOG, SALES, EMP]])
+ * LogicalTableScan(table=[[CATALOG, SALES, DEPT]])
+ * </pre></blockquote>
+ *
+ * <p> If the marker is used on only conjunctive predicates the optimizer
will try to translate
Review Comment:
Yes, it should be "used only in".
The output of MARK JOIN is as described in the first sentence of the
comment: An MARK JOIN will keep all rows from the left side and creates a new
attribute to mark a tuple as having join partners from right side or not. It
will not output the fields from the right side.
I looked at the SEMI/ANTI above — I think they implicitly represent (LEFT)
SEMI/ANTI, and therefore define MARK directly. Should I stay consistent with
that, or explicitly name it LEFT MARK? In my option, RIGHT MARK/SEMI/ANTI are
variants of LEFT MARK/SEMI/ANTI to support join commutativity. Should I define
them in this ticket?
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