Function invent_column_name

src/sql/src/plan/query.rs:3512–3628

`table_func_names` is a mapping from a UUID to the original function name. The UUIDs are identifiers that have been rewritten from some table function expression, and this mapping restores the original names.

(
    ecx: &ExprContext,
    expr: &Expr<Aug>,
    table_func_names: &BTreeMap<String, Ident>,
)

// name. The UUIDs are identifiers that have been rewritten from some table
// function expression, and this mapping restores the original names.
fn invent_column_name(
    ecx: &ExprContext,
    expr: &Expr<Aug>,
    table_func_names: &BTreeMap<String, Ident>,
) -> Result<Option<ColumnName>, PlanError> {
    // We follow PostgreSQL exactly here, which has some complicated rules
    // around "high" and "low" quality names. Low quality names override other
    // low quality names but not high quality names.
    //
    // See: https://github.com/postgres/postgres/blob/1f655fdc3/src/backend/parser/parse_target.c#L1716-L1728

    #[derive(Debug)]
    enum NameQuality {
        Low,
        High,
    }

    fn invent(
        ecx: &ExprContext,
        expr: &Expr<Aug>,
        table_func_names: &BTreeMap<String, Ident>,
    ) -> Result<Option<(ColumnName, NameQuality)>, PlanError> {
        Ok(match expr {
            Expr::Identifier(names) => {
                if let [name] = names.as_slice() {
                    if let Some(table_func_name) = table_func_names.get(name.as_str()) {
                        return Ok(Some((
                            normalize::column_name(table_func_name.clone()),
                            NameQuality::High,
                        )));
                    }
                }
                names
                    .last()
                    .map(|n| (normalize::column_name(n.clone()), NameQuality::High))
            }
            Expr::Value(v) => match v {
                // Per PostgreSQL, `bool` and `interval` literals take on the name
                // of their type, but not other literal types.
                Value::Boolean(_) => Some(("bool".into(), NameQuality::High)),
                Value::Interval(_) => Some(("interval".into(), NameQuality::High)),
                _ => None,
            },
            Expr::Function(func) => {
                let (schema, item) = match &func.name {
                    ResolvedItemName::Item {
                        qualifiers,
                        full_name,
                        ..
                    } => (&qualifiers.schema_spec, full_name.item.clone()),
                    // Name resolution should have rejected anything other than
                    // `Item` for a function call.
                    _ => {
                        bail_internal!("function name did not resolve to an item: {:?}", func.name)
                    }
                };

                if schema == &SchemaSpecifier::from(ecx.qcx.scx.catalog.get_mz_internal_schema_id())