Aleksandr Efimov created CALCITE-7844:
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Summary: Decimal division scale reduction uses total precision
instead of integral digits
Key: CALCITE-7844
URL: https://issues.apache.org/jira/browse/CALCITE-7844
Project: Calcite
Issue Type: Bug
Reporter: Aleksandr Efimov
With a custom type system allowing precision and scale 38, DECIMAL(18,6) /
DECIMAL(18,6) returns DECIMAL(38,6). The documented algorithm implies
DECIMAL(38,20).
In RelDataTypeSystem.deriveDecimalDivideType, the scale-reduction condition
compares total precision with the bound instead of integral digits.
Reproduced on main c425a5fa0; the same condition exists in 1.42.0. Related:
CALCITE-6464.
Correcting the condition also changes default inferred types: 95.0 / 100
becomes DECIMAL(14,12) instead of DECIMAL(14,6). Incorrect numeric values have
not been demonstrated.
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