Julian Hyde created CALCITE-7826:
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Summary: IS NOT DISTINCT FROM gives wrong result in Enumerable
convention when applied to DECIMAL values of different scales
Key: CALCITE-7826
URL: https://issues.apache.org/jira/browse/CALCITE-7826
Project: Calcite
Issue Type: Bug
Reporter: Julian Hyde
IS NOT DISTINCT FROM compares DECIMAL values using equals, so values with
different scales are distinct.
In the Enumerable convention, {{IS NOT DISTINCT FROM}} and {{IS DISTINCT FROM}}
are implemented by {{{}RexImpTable.DistinctFromImplementor{}}}, which compares
non-null operands using {{{}Objects.equals{}}}, and does not harmonize the
operand types (`harmonize` is `false`). For {{{}java.math.BigDecimal{}}},
{{equals}} is sensitive to scale, so 1.10 and 1.1 are distinct values. SQL's
{{=}} operator compares the same values numerically, and finds them equal. So
for non-null {{DECIMAL}} operands, {{x IS NOT DISTINCT FROM y}} and {{x = y}}
can disagree.
A query parsed from SQL is not affected.
{{StandardConvertletTable.convertIsDistinctFrom}} expands {{IS [NOT] DISTINCT
FROM}} using {{{}RelOptUtil.isDistinctFrom{}}}, so the plan uses {{IS NULL}}
and {{=}} on operands that have been cast to a common type; for example, {{a IS
NOT DISTINCT FROM b}} where {{a}} is {{DECIMAL(3, 2)}} and {{b}} is
{{DECIMAL(2, 1)}} becomes {{OR(AND(IS NULL(a), IS NULL(b)), IS TRUE(=(a,
CAST(b):DECIMAL(3, 2))))}}The {{IS_NOT_DISTINCT_FROM}} operator reaches
{{DistinctFromImplementor}} only if a plan calls it directly, for example using
{{{}RelBuilder.call(SqlStdOperatorTable.IS_NOT_DISTINCT_FROM, a, b){}}}.
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