tisyabhatia commented on code in PR #5127:
URL: https://github.com/apache/calcite/pull/5127#discussion_r3786214527
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core/src/test/java/org/apache/calcite/test/JdbcTest.java:
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@@ -1297,15 +1297,23 @@ private void checkResultSetMetaData(Connection
connection, String sql)
+ "c0=1998\n");
}
- /** Test case for [CALCITE-7594] GROUP BY ALL: grouping only by a constant
- * over empty input returns 0 rows. */
+ /** Test case for [CALCITE-7675] GROUP BY ALL over a select list whose only
+ * non-aggregate item is a constant.
+ *
+ * <p>The constant is not a grouping key, so no grouping key remains and the
+ * query is a single-group aggregation. It therefore returns one row even
+ * though the input is empty. Before [CALCITE-7675] the constant was a
+ * grouping key, empty input yielded no groups, and the query returned no
+ * rows. BigQuery documents the behavior asserted here: "If the set of
+ * inferred grouping keys is empty after exclusions are applied, all input
+ * rows are considered a single group for aggregation." */
@Test void testGroupByAllOverEmptyInput() {
CalciteAssert.hr()
.query("select 'x', count(*)\n"
+ "from \"hr\".\"emps\"\n"
+ "where false\n"
+ "group by all")
- .returnsCount(0);
+ .returns("EXPR$0=x; EXPR$1=0\n");
Review Comment:
This PR changes the rule, which I should have led with. Under CALCITE-7594
'x' was a grouping key, so empty input produced no groups; here keys come only
from expressions that depend on the input, so none remains and the query is a
single-group aggregation. I'm following BigQuery / DuckDB, which infers keys
only from expressions referencing a FROM name and treats an empty set like one
group.
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