I recently saw this post on the pg-hackers mailing list. If it turns
out to be true, it would be a nice feature which might prove to be
useful in porting acs 4.0.
Phil Steinke 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
