SOLVED - Re: Dynamic sql and variable record types

On Mar 20, 2008, at 5:28 PM, Erik Jones wrote:

> Hi, I've been working on a generic date partitioning system and I
> think I've reached something that can't be done, but I thought I'd
> post a question to the masses in the hope that I'm missing
> something. The basic idea of what I'm doing is some userland
> scripts that will accept a table name argument along with the name
> of a date/timestamp attribute to partition on and create partitions
> for that table along with the appropriate trigger and trigger
> function. The part I'm having trouble with is the trigger function.
>
> What I'm done for that is to create a template file that my scripts
> read in and substitute the table column names wherever necessary,
> then run the results through the db to create the functions. The
> problem is that for the function to be generic it needs to be able
> to work with different record/row types. Here's the template for
> function (not working, which I'll discuss below):
>
> CREATE OR REPLACE FUNCTION %s_ins_func(op text, rec %s)
> RETURNS boolean AS $$
> DECLARE
> partition varchar;
> name_parts varchar[];
> upper_dim integer;
> BEGIN
> FOR partition IN
> SELECT relname
> FROM pg_class
> WHERE relname ~ ('^%s_[0-9]{8}_[0-9]{8}$')
> LOOP
> name_parts := string_to_array(partition, '_');
> upper_dim := array_upper(name_parts, 1);
> IF rec.%s >= name_parts[upper_dim-1]::timestamp AND rec.%s <
> name_parts[upper_dim] THEN
> IF op = 'INSERT' THEN
> EXECUTE 'INSERT INTO %s_' || name_parts[upper_dim-1]
> || '_' ||
> name_parts[upper_dim] || ' VALUES ' ||
> rec || ';'; -- the problem is here with rec
> RETURN TRUE;
> END IF;
> END IF;
> END LOOP;
> RETURN FALSE;
> END;
> $$ language plpgsql;
>
> The userland scripts substitute the table and column names for the
> %s escapes where appropriate. What the function actually does is to
> us the parent table's name to find all of the child partitions which
> are name like some_table_20080101_20080201, split out the dates from
> those to determine which table the insert needs to be redirected
> to. That works fine. The problem is that since I have to
> dynamically generate the destination table name I have to use
> EXECUTE for the INSERT statement. But, I can't see how to use a
> record in query passed to EXECUTE. Am I right in thinking (now)
> that this can't be done?

I solved this by doing a lookup of the table's attributes and putting
them directly into the function during the templating step.

Erik Jones

DBA | Emma®
erik(at)myemma(dot)com
800.595.4401 or 615.292.5888
615.292.0777 (fax)

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