TJ Banghart created CALCITE-5616:
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Summary: Allow unparsing of SqlIntervalQualifier in EXTRACT to be
overridden by dialects
Key: CALCITE-5616
URL: https://issues.apache.org/jira/browse/CALCITE-5616
Project: Calcite
Issue Type: Improvement
Components: core
Reporter: TJ Banghart
In {{SqlExtractFunction#unparse}}, the first operand is passed to
{{SqlIntervalQualifier.asIdentifier}} which returns a {{SqlIdentifier}} [if the
operand is a
{{SqlIntervalQualifier}}|https://github.com/apache/calcite/blob/5c7be55ffee836366dcc7fefb6adfc0b8c47465f/core/src/main/java/org/apache/calcite/sql/SqlIntervalQualifier.java#L1366-L1370].
{{SqlIdentifier#unparse}} is handled by
[{{SqlUtil#unparseSqlIdentifierSyntax}}|https://github.com/apache/calcite/blob/5c7be55ffee836366dcc7fefb6adfc0b8c47465f/core/src/main/java/org/apache/calcite/sql/SqlUtil.java#L384-L412]
which has no dialect context.
We should unparse these interval identifiers in the target dialect using the
[existing {{SqlDialect#unparseSqlIntervalQualifier}}
method|https://github.com/apache/calcite/blob/5c7be55ffee836366dcc7fefb6adfc0b8c47465f/core/src/main/java/org/apache/calcite/sql/SqlDialect.java#L492-L538].
This would help prevent errors when unparsing interval identifiers for some
dialects.
For example, BigQuery uses {{DAYOFWEEK}} rather than {{DOW}} but there is
currently no way to override this in {{BigQuerySqlDialect}}.
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