Alessandro Solimando created CALCITE-4354:
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Summary: ITEM operator does not support synthetic struct type
Key: CALCITE-4354
URL: https://issues.apache.org/jira/browse/CALCITE-4354
Project: Calcite
Issue Type: Improvement
Components: core
Affects Versions: 1.27.0
Reporter: Alessandro Solimando
The current implementation of the "ITEM" operator only supports struct/row type
when this type if based on a class with named fields (that is, a non-synthetic
type).
For those non-synthetic struct types, the "ITEM" operator can be used to access
named fields via a "string"-typed argument
([SqlItemOperator#96|https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/sql/fun/SqlItemOperator.java#L96]).
The type checker accepts to apply "ITEM" on "ANY" type
([SqlItemOperator#49|https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/sql/fun/SqlItemOperator.java#L49]),
and the operand checker only accepts "string"-based values
([SqlItemOperator.java#105|https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/sql/fun/SqlItemOperator.java#L105]).
[SqlValidatorTest.java#L11933|https://github.com/apache/calcite/blob/master/core/src/test/java/org/apache/calcite/test/SqlValidatorTest.java#L11933]
is an example of application of the "ITEM" operator over a struct with named
fields.
However, the “getAllowedSignatures” method
([SqlItemOperator.java#116|https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/sql/fun/SqlItemOperator.java#L116])
does not reflect this, and asserts a signature as follows:
"<ARRAY>[<INTEGER>]" or "<MAP>[<VALUE>]".
"ITEM" operator could be enriched with the support of synthetic struct/row
type, with a positional access to the fields with a signature
"<ROW>[<INTEGER>]".
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