Claude Brisson created CALCITE-6402:
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Summary: Aggregates implied in grouping sets have a wrong
nullability at validation stage
Key: CALCITE-6402
URL: https://issues.apache.org/jira/browse/CALCITE-6402
Project: Calcite
Issue Type: Bug
Components: core
Affects Versions: 1.36.0
Reporter: Claude Brisson
As long as the empty set is present among the grouping sets, which is always
the case for CUBE and ROLLAP, the (unfiltered) result will contain a row with
the global aggregate. And on such a row, most standard aggregate functions are
nullable (even on a non-null column, for the empty rowset).
But the SUM function, for instance, has the following return type inference:
{code}
public static final SqlReturnTypeInference AGG_SUM = opBinding -> {
final RelDataTypeFactory typeFactory = opBinding.getTypeFactory();
final RelDataType type = typeFactory.getTypeSystem()
.deriveSumType(typeFactory, opBinding.getOperandType(0));
if (opBinding.getGroupCount() == 0 || opBinding.hasFilter()) {
return typeFactory.createTypeWithNullability(type, true);
} else {
return type;
}
};
{code}
If the operand is not nullable, since the group count will be non-zero for a
rollup, a cube or a grouping sets containing the empty set.
It seems to me that the group count itself is not a sufficient information to
determine the nullability, we may be lacking a boolean stating whether the
empty group is implied, or the complete list of groups instead of the groups
count.
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