Dropping -hackers; that list is for development of the database engine itself.

The problem is that rules will happen before triggers, so what you're trying to do will never work. Instead, just have the trigger insert the data into the appropriate table.

On May 30, 2007, at 9:55 AM, Enrico Sirola wrote:


I'm trying to write a trigger on insert which should insert the row in another table. The table on which to insert the row should be selected at runtime and
it is not know in advance. For example, let's say we have a table with
two columns, a date and an integer. a row is inserted into table XXX and

        refdate date;
        x2 integer;

when the statement

insert into XXX VALUES ('2007-11-11', 1);

is executed, a trigger (or rule) should be fired to insert the row into table XXX_20071111 (having the same schema). If the XXX_* tables are created beforehand this is not a problem because you can set up a rule for each date performing the needed insert (as documented in http://www.postgresql.org/docs/ 8.1/interactive/ddl-partitioning.html)

The problem arises when you try to extend the trigger in order to also dinamically
perform table creation is the XXX_20071111 doesn't exist:

I have, for example:

CREATE OR REPLACE FUNCTION add_child_table(parent_name varchar, d date)
RETURNS varchar AS $$
        new_table_name varchar;
      raise notice '%', 'creating table';
new_table_name := date2tblname(parent_name, d); -- converts table name and date into child table name execute 'CREATE TABLE ' || new_table_name || ' ( ) INHERITS (' || parent_name || ')';
        execute 'CREATE RULE '
                || new_table_name
                || '_insert AS ON INSERT TO '
                || parent_name
|| ' WHERE ( refdate = DATE ' /* refdate is the field we use to partition */
                || '''' || d || ''''
                || ' ) DO INSTEAD INSERT INTO '
                || new_table_name
                || ' VALUES ( NEW.* )';
        return new_table_name;
$$ LANGUAGE plpgsql;

I can use the above to add a child table and the rule to implement partitioning

CREATE OR REPLACE FUNCTION child_creation_trigger()
RETURNS "trigger" AS $$
        IF ( child_exist(TG_RELNAME::text, NEW.refdate) = false ) THEN
raise notice '%', 'creating ' || TG_RELNAME::text || ' for ' || NEW.refdate::text;
              perform add_child_table(TG_RELNAME::text, NEW.refdate);
--insert into ' || child_table_name || ' values ( NEW.* );
              RETURN NEW;
raise notice '%', 'NOT creating ' || TG_RELNAME::text || ' for ' || NEW.refdate::text;
              RETURN NEW;
        END IF;
$$ LANGUAGE plpgsql;

The trigger function is hooked to the to-be-partitioned table

execute procedure child_creation_trigger ();

now, every time I insert a tuple into XXX, the trigger is fired and checks if the needed table exists or not. If not, it creates the table and rule and goes on. The problem is that in this case the first row is inserted into the XXX table, not in the (just created) XXX_<refdate> . Then I tried to insert the row myself from the trigger body (and return null in order to skip the original insertion), but I'm not able to do it (see the commented insert in the above IF clause) because I can't properly
quote the target table name.
I shoud perform a

insert into child_table_name values (NEW.*);

obviously written like this the plpgsql complains at runtime because child_table_name is not a table name.
If, on the other side, I dynamically create the query like in

execute 'insert into ' || child_table_name || ' values (NEW.*)';

it complains because NEW in the execution context is unknown.

This should be a rather common problem... Isn't it? Is there a canonical way to solve it? Maybe there's a trivial answer, but I have no plpgsql programming

Thanks a lot in advance,

Enrico Sirola

Jim Nasby                                            [EMAIL PROTECTED]
EnterpriseDB      http://enterprisedb.com      512.569.9461 (cell)

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