Zhengqiang Duan created CALCITE-6645:
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Summary: Support user-defined function without parentheses when db
dialect's allowNiladicParentheses property is false
Key: CALCITE-6645
URL: https://issues.apache.org/jira/browse/CALCITE-6645
Project: Calcite
Issue Type: Improvement
Affects Versions: 1.38.0
Reporter: Zhengqiang Duan
Assignee: Zhengqiang Duan
Hi community, When I implement a user defined function without parameters for
Oracle database, I get a `Column 'SYS_DATE' not found in any table` exception
when I execute the `SELECT SYS_DATE FROM DUAL` statement. I did some research
and found that the default SqlSyntax used by the SqlUserDefinedFunction is
SqlSyntax.FUNCTION, and its corresponding function syntax is SYS_DATE() instead
of SYS_DATE. SqlSyntax.FUNCTION will cause an exception during SQL validation.
The implementation logic of makeNullaryCall in SqlValidatorImpl is as follows,
since makeNullaryCall checks if operator.getSyntax() == SqlSyntax.FUNCTION_ID,
user defined function cannot be converted to SqlBasicCall.
{code:java}
@Override
public @Nullable SqlCall makeNullaryCall(SqlIdentifier id) {
if (id.names.size() == 1 && !id.isComponentQuoted(0)) {
final List<SqlOperator> list = new ArrayList<>();
opTab.lookupOperatorOverloads(id, null, SqlSyntax.FUNCTION, list,
catalogReader.nameMatcher());
for (SqlOperator operator : list) {
if (operator.getSyntax() == SqlSyntax.FUNCTION_ID) {
// Even though this looks like an identifier, it is a
// actually a call to a function. Construct a fake
// call to this function, so we can use the regular
// operator validation.
return new SqlBasicCall(operator, ImmutableList.of(),
id.getParserPosition(), null).withExpanded(true);
}
}
}
return null;
}{code}
In order to support user defined functions without parameters, we need to
modify the logic of the CalciteCatalogReader#toOp method. If the current user
defined function has no parameters and allowNiladicParentheses is set to false,
SqlSyntax.FUNCTION_ID should be passed in for SqlUserDefinedFunction.
{code:java}
SqlSyntax syntax = function.getParameters().isEmpty()
&& !config.conformance().allowNiladicParentheses()
? SqlSyntax.FUNCTION_ID
: SqlSyntax.FUNCTION;
return new SqlUserDefinedFunction(name, kind, returnTypeInference,
operandTypeInference, operandMetadata, function, syntax);{code}
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