You can bind a trigger function to as many tables as you want; just execute a CREATE TRIGGER statement for each binding. Make sure to schema-qualify the table name in your statement (BEFORE INSERT OR UPDATE ON a.point etc.)

If the trigger function needs to do something different depending on which table it's running on, you can access the table schema and name through TG_TABLE_SCHEMA and TG_TABLE_NAME. (See the docs for all available variables).

If you have a large number of schemas, you could generate the SQL dynamically by iterating over the rows in information_schema.schemata.

You can bind a trigger function to as many tables as you want; just execute a CREATE TRIGGER statement for each binding. Make sure to schema-qualify the table name in your statement (BEFORE INSERT OR UPDATE ON a.point etc.) If you have a large number of schemas, you could generate the SQL dynamically by iterating over the rows in information_schema.schemata.

If the trigger function needs to do something different depending on which table it's running on, you can access the table schema and name through TG_TABLE_SCHEMA and TG_TABLE_NAME. (See the docs for all available variables).

In your case, a dynamic trigger function might be something like this:

CREATE OR REPLACE FUNCTION sample_attribute_from_polygon()
RETURNS trigger AS $body$
    BEGIN
    EXECUTE 'SELECT attribute FROM ' || TG_TABLE_SCHEMA || '.polygon WHERE ST_Within($1, polygon.geom) LIMIT 1' 
      USING NEW.geom 
      INTO NEW.attribute_sample;
    RETURN NEW;
    END;
$body$ LANGUAGE plpgsql;