Re: Parameters don't work in FETCH NEXT clause?

Shay Rojansky <roji(at)roji(dot)org> writes:
> A user of mine just raised a strange issue... While it is possible to use a
> parameter in a LIMIT clause, PostgreSQL does not seem to allow using one in
> a FETCH NEXT clause. In other words, while the following works:
> SELECT 1 LIMIT $1;
> The following generates a syntax error:
> SELECT 1 FETCH NEXT $1 ROWS ONLY;
> Since LIMIT and FETCH NEXT are supposed to be equivalent this behavior is
> odd.

Per the SELECT reference page:

SQL:2008 introduced a different syntax to achieve the same result,
which PostgreSQL also supports. It is:

OFFSET start { ROW | ROWS }
FETCH { FIRST | NEXT } [ count ] { ROW | ROWS } ONLY

In this syntax, to write anything except a simple integer constant for
start or count, you must write parentheses around it.

The comments about this in gram.y are informative:

* Allowing full expressions without parentheses causes various parsing
* problems with the trailing ROW/ROWS key words. SQL only calls for
* constants, so we allow the rest only with parentheses. If omitted,
* default to 1.

regards, tom lane