Re: ORDER BY $1 behaves inconsistently

Thanks for the explanation - that makes sense.

On Fri, Oct 27, 2017 at 2:33 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> Jordan Lewis <jordanthelewis(at)gmail(dot)com> writes:
> > Actually, it's even worse than I thought. It seems that placeholders in
> > ORDER BY clauses get entirely ignored,
> > as running `EXECUTE x(1)` on the previous example with unsorted table
> data
> > does not sort the table by the 1st
> > column as expected.
>
> "ORDER BY $1" is asking to order by some constant value (constant within
> any one execution of the command, anyway), which is useless, because all
> rows in the query will have the same sort key. The planner will throw
> that away as being a no-op.
>
> "ORDER BY 1" is asking to order by the first output column. This is
> not the same thing. You cannot get that effect with a parameter;
> if you could, it would probably represent a SQL-injection hazard.
>
> If the value of $1 were "foo" and you complained that it didn't order
> by column foo, it would be exactly the same issue...
>
> regards, tom lane
>