Function plan_solitary_table_function

src/sql/src/plan/query.rs:3228–3274

Plans a table function that appears alone, i.e., that is not part of a `ROWS FROM` clause that contains other table functions. Special aliasing rules apply.

(
    qcx: &QueryContext,
    function: &Function<Aug>,
    alias: Option<&TableAlias>,
    with_ordinality: bool,
)

/// FROM` clause that contains other table functions. Special aliasing rules
/// apply.
fn plan_solitary_table_function(
    qcx: &QueryContext,
    function: &Function<Aug>,
    alias: Option<&TableAlias>,
    with_ordinality: bool,
) -> Result<(HirRelationExpr, Scope), PlanError> {
    let (expr, mut scope) = plan_table_function_internal(qcx, function, with_ordinality, None)?;

    let single_column_function = scope.len() == 1 + if with_ordinality { 1 } else { 0 };
    if single_column_function {
        let item = &mut scope.items[0];

        // Mark that the function only produced a single column. This impacts
        // whole-row references.
        item.from_single_column_function = true;

        // Strange special case for solitary table functions that output one
        // column whose name matches the name of the table function. If a table
        // alias is provided, the column name is changed to the table alias's
        // name. Concretely, the following query returns a column named `x`
        // rather than a column named `generate_series`:
        //
        //     SELECT * FROM generate_series(1, 5) AS x
        //
        // Note that this case does not apply to e.g. `jsonb_array_elements`,
        // since its output column is explicitly named `value`, not
        // `jsonb_array_elements`.
        //
        // Note also that we may (correctly) change the column name again when
        // we plan the table alias below if the `alias.columns` is non-empty.
        if let Some(alias) = alias {
            if let ScopeItem {
                table_name: Some(table_name),
                column_name,
                ..
            } = item
            {
                if table_name.item.as_str() == column_name.as_str() {
                    *column_name = normalize::column_name(alias.name.clone());
                }
            }
        }
    }

    let scope = plan_table_alias(scope, alias)?;
    Ok((expr, scope))
}

/// Plans a table function.
///