The parser does its work without looking at the operator table. (Like any sane parser, it deals only with syntax, not semantics.) So, it’s impossible for your TRIM function to affect what the parser considers to be valid.
One option is for you to modify the Babel parser, which is a more lenient variant of the parser. For example, it allows DATE as a function: https://issues.apache.org/jira/browse/CALCITE-3022. Julian > On Mar 5, 2024, at 2:18 PM, Xiaoying Wang <wangxiaoying0...@gmail.com> wrote: > > Hi community, > > I want to override the `trim` function. Currently the function it cannot > support signature like this: `trim(string, characters)`, which is supported > by database like DuckDB[1]. > > I implemented a function like the following: > > ``` > public class SqlTrim2Function extends SqlFunction { > public static final SqlTrim2Function INSTANCE = new SqlTrim2Function(); > public SqlTrim2Function() { > super( > "TRIM", > SqlKind.OTHER_FUNCTION, > ReturnTypes.VARCHAR, > null, > OperandTypes.STRING > .or(OperandTypes.sequence("TRIM(<STRING>, > <STRING>)", > OperandTypes.STRING, OperandTypes.STRING)), > SqlFunctionCategory.STRING); > } > } > ``` > > and added to the operator table like this: > > ``` > SqlOperatorTable sqlOperatorTable = SqlOperatorTables.chain( > SqlOperatorTables.of( > SqlTrim2Function.INSTANCE > ) > ); > > FrameworkConfig frameworkConfig = Frameworks.newConfigBuilder() > ... > .operatorTable(sqlOperatorTable) > ... > .build(); > ``` > > However, I still got the parsing error (saying there is a ','). > > The reason is that the `TRIM` expression directly goes to the > `BuiltinFunctionCall` since `jj_2_60(2)` is true inside > `AtomicRowExpression` of `SqlParserImpl` instead of goes to > `NamedFunctionCall·. So it does not goes to the function I defined. > > Currently I workaround this by changing the function name to `trim2` so > that it is not recognized as a built-in function, which works but is not > ideal. Is there a easy way to override the `trim` function inside > SqlParserImpl (seems like it is generated)? > > Best, > Xiaoying > > > [1] https://duckdb.org/docs/sql/functions/char.html
