Re: plpgsql variable trouble

Phil Steinke <lintec(at)engsoc(dot)queensu(dot)ca> writes:
> The problem with my code seems to be that the "given_field" variable isn't
> being interpolated in the assignment statement.

plpgsql is not a string-substitution language; you cannot expect the
value of a variable to be used as a table or field name in a query.
This is true because plpgsql precompiles queries into query plans
and saves the plans for repeated execution. That's a win for speed
but costs flexibility.

You *can* get that sort of result in pltcl or plperl, which don't do
any fancy caching. You just form the query as a string value using the
usual expression evaluation rules of those languages, and that string
gets submitted to the SQL parser and query engine. Less speed, more
flexibility.

I believe 7.1's plpgsql will have an EXECUTE <string> command that lets
you get the second effect in plpgsql too.

regards, tom lane