[GitHub] [calcite] zabetak commented on a change in pull request #2393: [CALCITE-4574] Wrong/Invalid plans when using RelBuilder#join with correlations

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zabetak commented on a change in pull request #2393:
URL: https://github.com/apache/calcite/pull/2393#discussion_r613992188



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File path: core/src/main/java/org/apache/calcite/tools/RelBuilder.java
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@@ -2368,24 +2368,28 @@ public RelBuilder join(JoinRelType joinType, RexNode condition,
     }
     if (correlate) {
       final CorrelationId id = Iterables.getOnlyElement(variablesSet);
-      final ImmutableBitSet requiredColumns =
-          RelOptUtil.correlationColumns(id, right.rel);
       if (!RelOptUtil.notContainsCorrelation(left.rel, id, Litmus.IGNORE)) {
         throw new IllegalArgumentException("variable " + id
             + " must not be used by left input to correlation");
       }
+      // Correlate does not have an ON clause.
       switch (joinType) {
       case LEFT:
-        // Correlate does not have an ON clause.
-        // For a LEFT correlate, predicate must be evaluated first.
-        // For INNER, we can defer.
+      case SEMI:
+      case ANTI:
+        // For a LEFT/SEMI/ANTI, predicate must be evaluated first.
         stack.push(right);
         filter(condition.accept(new Shifter(left.rel, id, right.rel)));
         right = stack.pop();
         break;
-      default:
+      case INNER:
+        // For INNER, we can defer.
         postCondition = condition;
+        break;
+      default:
+        throw new IllegalArgumentException("Correlated " + joinType + " join is not supported");
       }
+      final ImmutableBitSet requiredColumns = RelOptUtil.correlationColumns(id, right.rel);

Review comment:
       Correlation has slightly different semantics than join so I am not sure if it is always safe to perform this transformation. It may be but we should tackle it in another JIRA/PR to avoid complicating this case.




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