With inheritance like @Denis mentioned, this would be very simple. Works for Postgres 8.4, too. Be sure to consider the limitations.
Basically, you would have a master table, I suppose in a master schema:
CREATE TABLE master.product (title text);
And all other tables in various schemata inherit from it, possibly adding more local columns:
CREATE TABLE a.product (product_id serial PRIMARY KEY, col2 text)
INHERITS (master.product);
CREATE TABLE b.product (product_id serial PRIMARY KEY, col2 text, col3 text)
INHERITS (master.product);
etc.
The tables don't have to share the same name or schema.
Then you can query all tables in a single fell swoop:
SELECT title, tableoid::regclass::text AS source
FROM master.product
WHERE title ILIKE '%test%';
tableoid::regclass::text
?
That's a handy way to tell the source of each row. Details: