On 14/03/2006, at 12:05 AM, Michael Fuhr wrote:
On Mon, Mar 13, 2006 at 10:45:47PM -0800, Nick Johnson wrote:
Can anyone provide me with some direction on how to write a function
I can load into postgres that will execute a function specified by
OID (or regproc/regprocedure) at runtime, with type safety? I've been
able to write such a function in C, but I was unable to figure out
how to determine the parameters that the specified function expects,
so I can prevent calling a function that doesn't match the expected
signature (which segfaults postgres).
Does the calling function have to be written in C? In PL/pgSQL you
could easily query pg_proc with the oid to get the called function's
name, argument types, etc., then build an appropriate string to
EXECUTE.
I considered this, but I'd rather not do it by string manipulation
and dynamic SQL - it seems a kludge.
In C you could use SearchSysCache() and SysCacheGetAttr();
search through the source code for examples of calls to those
functions with a first argument of PROCOID.
Thanks for the tips.
Why do you need to do this? What problem are you trying to solve?
I want to associate Postgres functions with rows of a table (eg, a
table column of datatype regproc or regprocedure) and be able to
execute the function associated with that row in a query.
-Nick Johnson
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