[GitHub] [calcite] zstan commented on a change in pull request #2439: CALCITE-4652 AggregateExpandDistinctAggregatesRule must cast top aggregates to original type

[GitBox <gi...@apache.org>]

zstan commented on a change in pull request #2439:
URL: https://github.com/apache/calcite/pull/2439#discussion_r662016102



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File path: core/src/main/java/org/apache/calcite/rel/rules/AggregateExpandDistinctAggregatesRule.java
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@@ -366,12 +370,18 @@ private static RelBuilder convertSingletonDistinct(RelBuilder relBuilder,
         final int arg = bottomGroups.size() + nonDistinctAggCallProcessedSoFar;
         final List<Integer> newArgs = ImmutableList.of(arg);
         if (aggCall.getAggregation().getKind() == SqlKind.COUNT) {
+          RelDataTypeFactory typeFactory = aggregate.getCluster().getTypeFactory();
+          RelDataType sumType = typeFactory.getTypeSystem().deriveSumType(typeFactory,
+              aggCall.getType());
+          needTopCast |= !sumType.equals(aggCall.getType());

Review comment:
       running new test under debug, i found aggCall.getType() == BIGINT, while sumType == DECIMAL(19, 0) all these representation are identical as i can see, can you explain why we rise needTopCast flag in this case? Additionally i hope we need integration test highliting the bug, ServerTest possibly correct place for it. wdyt ?




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