gustavodemorais commented on code in PR #26702:
URL: https://github.com/apache/flink/pull/26702#discussion_r2157018521
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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].
+ *
+ * @param join Join or MultiJoin node
+ * @return set of all the join keys (keys from join conditions)
+ */
+ public Set<String> getJoinKeys(RelNode join) {
+ Set<String> joinKeys = new HashSet<>();
+ List<RexCall> conditions = Collections.emptyList();
+ List<RelNode> inputs = join.getInputs();
+
+ if (join instanceof Join) {
+ conditions = collectConjunctions(((Join) join).getCondition());
+ } else if (join instanceof MultiJoin) {
+ conditions =
+ ((MultiJoin) join)
+ .getOuterJoinConditions().stream()
+ .flatMap(cond ->
collectConjunctions(cond).stream())
+ .collect(Collectors.toList());
+ }
+
+ RelMetadataQuery mq = join.getCluster().getMetadataQuery();
+
+ for (RexCall condition : conditions) {
+ for (RexNode operand : condition.getOperands()) {
+ if (operand instanceof RexInputRef) {
+ addJoinKeysByOperand((RexInputRef) operand, inputs, mq,
joinKeys);
+ }
+ }
+ }
+
+ return joinKeys;
+ }
+
+ /**
+ * Retrieves conjunctions from joinCondition.
+ *
+ * @param joinCondition join condition
+ * @return List of RexCalls representing conditions
+ */
+ private List<RexCall> collectConjunctions(RexNode joinCondition) {
Review Comment:
~We need to filter out non equiJoin conditions here or in
addJoinKeysByOperand~ Actually this already happens when you do `(operand
instanceof RexInputRef)`
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