Method show_functions_to_plan

datafusion/sql/src/statement.rs:2562–2634

Rewrite `SHOW FUNCTIONS` to another SQL query The query is based on the `information_schema.routines` and `information_schema.parameters` tables The output columns: - function_name: The name of function - return_type: The return type of the function - parameters: The name of parameters (ordered by the ordinal position) - parameter_types: The type of parameters (ordered by the ordinal position) -

(
        &self,
        filter: Option<ShowStatementFilter>,
    )

    /// - description: The description of the function (the description defined in the document)
    /// - syntax_example: The syntax_example of the function (the syntax_example defined in the document)
    fn show_functions_to_plan(
        &self,
        filter: Option<ShowStatementFilter>,
    ) -> Result<LogicalPlan> {
        let where_clause = if let Some(filter) = filter {
            match filter {
                ShowStatementFilter::Like(like) => {
                    format!("WHERE p.function_name like '{like}'")
                }
                _ => return plan_err!("Unsupported SHOW FUNCTIONS filter"),
            }
        } else {
            "".to_string()
        };

        let query = format!(
            r#"
SELECT DISTINCT
    p.*,
    r.function_type function_type,
    r.description description,
    r.syntax_example syntax_example
FROM
    (
        SELECT
            i.specific_name function_name,
            o.data_type return_type,
            array_agg(i.parameter_name ORDER BY i.ordinal_position ASC) parameters,
            array_agg(i.data_type ORDER BY i.ordinal_position ASC) parameter_types
        FROM (
                 SELECT
                     specific_catalog,
                     specific_schema,
                     specific_name,
                     ordinal_position,
                     parameter_name,
                     data_type,
                     rid
                 FROM
                     information_schema.parameters
                 WHERE
                     parameter_mode = 'IN'
             ) i
                 JOIN
             (
                 SELECT
                     specific_catalog,
                     specific_schema,
                     specific_name,
                     ordinal_position,
                     parameter_name,
                     data_type,
                     rid
                 FROM
                     information_schema.parameters
                 WHERE
                     parameter_mode = 'OUT'
             ) o