zabetak commented on a change in pull request #884: [CALCITE-2621] New rule:
SemiJoinToCorrelateRule (SemiJoin => LogicalCorrelate) (Ruben Quesada Lopez)
URL: https://github.com/apache/calcite/pull/884#discussion_r261641280
##########
File path:
core/src/main/java/org/apache/calcite/rel/rules/JoinToCorrelateRule.java
##########
@@ -56,31 +60,57 @@
*
* <p>would require emitting a NULL emp row if a certain department contained
no
* employees, and Correlator cannot do that.</p>
+ *
+ * <p>There is a constructor parameterized to allow any sub-class of
+ * {@link org.apache.calcite.rel.core.Join}, not just
+ * {@link org.apache.calcite.rel.logical.LogicalJoin}.</p>
*/
public class JoinToCorrelateRule extends RelOptRule {
+
+ private final Function<Join, SemiJoinType> semiJoinTypeFunction;
+
//~ Static fields/initializers ---------------------------------------------
public static final JoinToCorrelateRule INSTANCE =
new JoinToCorrelateRule(RelFactories.LOGICAL_BUILDER);
+ /**
+ * Rule that converts a {@link org.apache.calcite.rel.core.SemiJoin}
+ * into a {@link org.apache.calcite.rel.logical.LogicalCorrelate}
+ */
+ public static final JoinToCorrelateRule SEMI =
+ new JoinToCorrelateRule(SemiJoin.class,
+ RelFactories.LOGICAL_BUILDER, join -> SemiJoinType.SEMI);
+
//~ Constructors -----------------------------------------------------------
/**
* Creates a JoinToCorrelateRule.
*/
public JoinToCorrelateRule(RelBuilderFactory relBuilderFactory) {
- super(operand(LogicalJoin.class, any()), relBuilderFactory, null);
+ this(LogicalJoin.class, relBuilderFactory, join ->
SemiJoinType.of(join.getJoinType()));
}
@Deprecated // to be removed before 2.0
protected JoinToCorrelateRule(RelFactories.FilterFactory filterFactory) {
this(RelBuilder.proto(Contexts.of(filterFactory)));
}
+ /**
+ * Creates a JoinToCorrelateRule for a certain sub-class of
+ * {@link org.apache.calcite.rel.core.Join}
+ */
+ public JoinToCorrelateRule(Class<? extends Join> clazz,
+ RelBuilderFactory relBuilderFactory,
+ Function<Join, SemiJoinType>
semiJoinTypeFunction) {
Review comment:
(Minor suggestion) Maybe rename the `semiJoinTypeFunction` to something
better illustrating what does it do. Something like `semiJoinTypeExtractor`,
`semiJoinTypeMapper`, etc.
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