Vladimir Sitnikov created CALCITE-7847:
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Summary: Implicit coercion casts MULTISET operands of a comparison
to ARRAY, and loses the nullability of ROW operands
Key: CALCITE-7847
URL: https://issues.apache.org/jira/browse/CALCITE-7847
Project: Calcite
Issue Type: Bug
Components: core
Affects Versions: 1.42.0
Reporter: Vladimir Sitnikov
Comparing two MULTISET values whose element types differ casts both operands to
ARRAY. On main (commit 843f468405, 1.43.0-SNAPSHOT), SqlToRelConverter
translates
{code:sql}
select multiset[deptno] = multiset[cast(deptno as decimal(5, 2))] from dept
{code}
into
{noformat}
LogicalProject(EXPR$0=[=(CAST($SLICE($2)):DECIMAL(12, 2) NOT NULL ARRAY NOT
NULL, CAST($SLICE($3)):DECIMAL(12, 2) NOT NULL ARRAY NOT NULL)])
{noformat}
Expected: both operands are cast to {{DECIMAL(12, 2) NOT NULL MULTISET NOT
NULL}}.
{{AbstractTypeCoercion#commonTypeForBinaryComparison}}, which the coercion
calls, shows the same defect for the types directly:
||type1||type2||returned||expected||
|INTEGER NOT NULL MULTISET NOT NULL|CHAR(1) NOT NULL MULTISET NOT NULL|INTEGER
NOT NULL ARRAY NOT NULL|INTEGER NOT NULL MULTISET NOT NULL|
|RecordType(INTEGER a) (nullable)|RecordType(CHAR(1) NOT NULL a) NOT
NULL|RecordType(INTEGER a) NOT NULL|RecordType(INTEGER a) (nullable)|
The other branches of the method, ARRAY and MAP included, return a nullable
type when either operand is nullable (CALCITE-6741); the ROW branch returns NOT
NULL. I did not find a query where the ROW defect changes the plan:
SqlToRelConverter expands a ROW comparison into comparisons of its fields, so
it shows only to callers of the method, such as a custom TypeCoercion.
Cause: the ARRAY and MULTISET branch of {{commonTypeForBinaryComparison}}
recurses into the element type for both, then always builds the result with
{{createArrayType}}; the ROW branch returns {{createStructType(resultFields)}}
without applying the nullability of the operands. The MULTISET branch came with
CALCITE-6736, the ROW branch with CALCITE-6735.
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