Function plan_subscript

src/sql/src/plan/query.rs:4326–4365

(
    ecx: &ExprContext,
    expr: &Expr<Aug>,
    positions: &[SubscriptPosition<Aug>],
)

}

fn plan_subscript(
    ecx: &ExprContext,
    expr: &Expr<Aug>,
    positions: &[SubscriptPosition<Aug>],
) -> Result<CoercibleScalarExpr, PlanError> {
    assert!(
        !positions.is_empty(),
        "subscript expression must contain at least one position"
    );

    let ecx = &ecx.with_name("subscripting");
    let expr = plan_expr(ecx, expr)?.type_as_any(ecx)?;
    let ty = ecx.scalar_type(&expr);
    match &ty {
        SqlScalarType::Array(..) | SqlScalarType::Int2Vector => plan_subscript_array(
            ecx,
            expr,
            positions,
            // Int2Vector uses 0-based indexing, while arrays use 1-based indexing, so we need to
            // adjust all Int2Vector subscript operations by 1 (both w/r/t input and the values we
            // track in its backing data).
            if ty == SqlScalarType::Int2Vector {
                1
            } else {
                0
            },
        ),
        SqlScalarType::Jsonb => plan_subscript_jsonb(ecx, expr, positions),
        SqlScalarType::List { element_type, .. } => {
            // `elem_type_name` is used only in error msgs, so we set `postgres_compat` to false.
            let elem_type_name = ecx.humanize_sql_scalar_type(element_type, false);
            let n_layers = ty.unwrap_list_n_layers();
            plan_subscript_list(ecx, expr, positions, n_layers, &elem_type_name)
        }
        ty => sql_bail!(
            "cannot subscript type {}",
            ecx.humanize_sql_scalar_type(ty, false)
        ),
    }
}

// All subscript positions are of the form [<expr>(:<expr>?)?]; extract all
// expressions from those that look like indexes (i.e. `[<expr>]`) or error if