gustavodemorais commented on code in PR #26702:
URL: https://github.com/apache/flink/pull/26702#discussion_r2156784343
##########
flink-table/flink-table-planner/src/main/java/org/apache/flink/table/planner/plan/rules/logical/JoinToMultiJoinRule.java:
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@@ -546,12 +557,140 @@ private boolean canCombine(
} else {
return false;
}
- return true;
+ return haveCommonJoinKey(origJoin, join);
} else {
return false;
}
}
+ /**
+ * Checks if original Join and child multi-join have common join keys.
+ *
+ * @param origJoin original Join
+ * @param otherJoin child MultiJoin
+ * @return true if original Join and child multi-join have at least one
common JoinKey
+ */
+ private boolean haveCommonJoinKey(Join origJoin, MultiJoin otherJoin) {
+ Set<String> origJoinKeys = getJoinKeys(origJoin);
+ Set<String> otherJoinKeys = getJoinKeys(otherJoin);
+
+ origJoinKeys.retainAll(otherJoinKeys);
+
+ return !origJoinKeys.isEmpty();
+ }
+
+ /**
+ * Gives set of join keys as strings like [table_name.field_name].
Review Comment:
Suggestion: `Returns a set of join keys as strings following this format
[table_name.field_name].`
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