Function plan_set_expr

src/sql/src/plan/query.rs:1827–2073

(
    qcx: &mut QueryContext,
    q: &SetExpr<Aug>,
)

}

fn plan_set_expr(
    qcx: &mut QueryContext,
    q: &SetExpr<Aug>,
) -> Result<(HirRelationExpr, Scope), PlanError> {
    match q {
        SetExpr::Select(select) => {
            let order_by_exprs = Vec::new();
            let plan = plan_select_from_where(qcx, *select.clone(), order_by_exprs)?;
            // We didn't provide any `order_by_exprs`, so `plan_select_from_where`
            // should not have planned any ordering.
            assert!(plan.order_by.is_empty());
            Ok((plan.expr.project(plan.project), plan.scope))
        }
        SetExpr::SetOperation {
            op,
            all,
            left,
            right,
        } => {
            // Plan the LHS and RHS.
            let (left_expr, left_scope) = qcx.checked_recur_mut(|qcx| plan_set_expr(qcx, left))?;
            let (right_expr, right_scope) =
                qcx.checked_recur_mut(|qcx| plan_set_expr(qcx, right))?;

            // Validate that the LHS and RHS are the same width.
            let left_type = qcx.relation_type(&left_expr);
            let right_type = qcx.relation_type(&right_expr);
            if left_type.arity() != right_type.arity() {
                sql_bail!(
                    "each {} query must have the same number of columns: {} vs {}",
                    op,
                    left_type.arity(),
                    right_type.arity(),
                );
            }

            // Match the types of the corresponding columns on the LHS and RHS
            // using the normal type coercion rules. This is equivalent to
            // `coerce_homogeneous_exprs`, but implemented in terms of
            // `HirRelationExpr` rather than `HirScalarExpr`.
            let left_ecx = &ExprContext {
                qcx,
                name: &op.to_string(),
                scope: &left_scope,
                relation_type: &left_type,
                allow_aggregates: false,
                allow_subqueries: false,
                allow_parameters: false,
                allow_windows: false,
            };
            let right_ecx = &ExprContext {
                qcx,
                name: &op.to_string(),
                scope: &right_scope,
                relation_type: &right_type,
                allow_aggregates: false,
                allow_subqueries: false,
                allow_parameters: false,