PostgreSQL 9.3 trigger function to insert into table with parameterized name

问题

I'm trying to dynamically partition log entries in Postgres. I have 53 child tables (1 for each week's worth of log entries), and would like to route INSERTs to a child table using a trigger.

I run the function with INSERT INTO log5 VALUES (NEW.*), and it works.

I run the function with the EXECUTE statement instead, and it fails. Within the EXECUTE statement, it's recognizing NEW as a table name and not a variable passed to the trigger function. Any ideas on how to fix? Thanks!

The error:

QUERY: INSERT INTO log5 VALUES (NEW.*)
CONTEXT: PL/pgSQL function log_roll_test() line 6 at EXECUTE statement
ERROR: missing FROM-clause entry for table "new" SQL state: 42P01

My function:

CREATE FUNCTION log_roll_test() RETURNS trigger AS $body$
DECLARE t text;
BEGIN
    t := 'log' || extract(week FROM NEW.updt_ts); --child table name
    --INSERT INTO log5 VALUES (NEW.*);
    EXECUTE format('INSERT INTO %I VALUES (NEW.*);', t);
    RETURN NULL;
END;
$body$ LANGUAGE plpgsql;

My trigger:

CREATE TRIGGER log_roll_test
BEFORE INSERT ON log FOR EACH ROW
EXECUTE PROCEDURE log_roll_test();

回答1:

CREATE FUNCTION log_roll_test()
  RETURNS trigger AS
$func$
BEGIN
   EXECUTE format('INSERT INTO %I SELECT ($1).*'
                , to_char(NEW.updt_ts, '"log"WW'))   -- child table name
   USING NEW;
   RETURN NULL;
END
$func$ LANGUAGE plpgsql;

You cannot reference NEW inside the query string. NEW is visible in the function body, but not inside EXECUTE environment. The best solution is to pass the values in the USING clause.

I also substituted the equivalent to_char(NEW.updt_ts, '"log"WW') for the table name. to_char() is faster and simpler here.

来源：https://stackoverflow.com/questions/23247105/postgresql-9-3-trigger-function-to-insert-into-table-with-parameterized-name

标签

postgresql

triggers

plpgsql

dynamic-sql