Shilong Stanley Yao <yao@noao.edu> writes:
> I am trying to write a function in Postgresql, which takes 2 floats and
> returns a box. But seems the nested single-quote in the AS clause
> prevent $1 and $2 from being expanded. Besides writing a C function
> instead of a SQL one, is there any way to solve this problem?
> CREATE OR REPLACE FUNCTION func_radec_to_box(float, float) RETURNS box
> AS 'SELECT box \'(($1, $2), (1.3, 1.4))\''
> LANGUAGE 'sql'
> WITH (ISCACHABLE);
This is never going to work because you are trying to use the
typed-literal syntax with something that you don't actually want to
be a literal constant. You need to think in terms of a function, not
a literal. In this case I think what you want is the box-from-two-points
constructor function, together with the point-from-two-floats constructor:
... AS 'SELECT box(point($1, $2), point(1.3, 1.4))'
If you had a mind to, you could write the constant point as a literal:
... AS 'SELECT box(point($1, $2), point \'1.3, 1.4\')'
but you can't write the variable point as a literal.
regards, tom lane
