[GitHub] [calcite] hsyuan commented on a change in pull request #1410: [CALCITE-3287] Fix minor bug, getRowCount for union in RelMdRowCount.java not consider 'union all'

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hsyuan commented on a change in pull request #1410: [CALCITE-3287] Fix minor bug, getRowCount for union in RelMdRowCount.java not consider 'union all'
URL: https://github.com/apache/calcite/pull/1410#discussion_r317417476
 
 

 ##########
 File path: core/src/main/java/org/apache/calcite/rel/metadata/RelMdRowCount.java
 ##########
 @@ -83,15 +83,7 @@ public Double getRowCount(RelSubset subset, RelMetadataQuery mq) {
   }
 
   public Double getRowCount(Union rel, RelMetadataQuery mq) {
-    double rowCount = 0.0;
-    for (RelNode input : rel.getInputs()) {
-      Double partialRowCount = mq.getRowCount(input);
-      if (partialRowCount == null) {
-        return null;
-      }
-      rowCount += partialRowCount;
-    }
-    return rowCount;
+    return rel.estimateRowCount(mq);
 
 Review comment:
   `Union.estimateRowCount` doesn't take into account the case that one of the inputs might return null.

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