JingDas commented on code in PR #3264:
URL: https://github.com/apache/calcite/pull/3264#discussion_r1230251674
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core/src/main/java/org/apache/calcite/rel/metadata/BuiltInMetadata.java:
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@@ -105,6 +105,44 @@ interface Handler extends MetadataHandler<UniqueKeys> {
}
}
+ /**
+ * Metadata about which columns have foreign keys.
+ */
+ public interface ForeignKeys extends Metadata {
+ MetadataDef<ForeignKeys> DEF =
+ MetadataDef.of(ForeignKeys.class, ForeignKeys.Handler.class,
+ BuiltInMethod.FOREIGN_KEYS.method);
+
+ /**
+ * Determines the list of foreign keys for this expression. Foreign keys
are
+ * represented as an {@link org.apache.calcite.util.ImmutableBitSet}, where
+ * each bit position represents the column ordinal is foreign key.
+ *
+ * @param ignoreNulls if true, ignore null values when determining
Review Comment:
In our inner join removing scene. It will make a mistake when forein key is
nullable. because after removing inner join side which contains unique keys, If
foreign key is nullable, the result will contain some null foreign key result
wrongly.
In other scene, it maybe wants foreign keys containg null.
And BuiltInMetadata.ForeignKeys is a common component, so i add
"ignoreNulls"option for getForeignKeys method.
BuiltInMetadata.ForeignKeys can be used for different scene, and in our
scene it should not contains null.
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