Use a variable in a postgresql execute statement

Question

I am trying to have a parameter when creating a trigger function.

I have been trying to use this code:

DO $DO$
BEGIN
EXECUTE format($TRIGGER$
  CREATE OR REPLACE FUNCTION my_schema.my_trigger_fcn() RETURNS trigger AS
  $BODY$
    DECLARE
      my_geom geometry(MultiPoint,%1$s);
    BEGIN
      my_geom = st_collect(NEW.situation_geometry)::geometry(MultiPoint,%$1s);
      NEW.geometry = my_geom;
      RETURN NEW;
    END;
  $BODY$
  LANGUAGE plpgsql;
$TRIGGER$, :SRID);
END
$DO$;

and trying to run this code with psql -v SRID=2056 -f myfile. But I get a syntax error.

I have also tried the SQL execute command, but prepared statements are not allowed to create trigger function.

Any idea?

SOLUTION:

Thanks to @Pavel Stehule, here is the code that works:

SELECT set_config('my.srid', :SRID::text, false);
DO $DO$
BEGIN
EXECUTE format($TRIGGER$
  CREATE OR REPLACE FUNCTION qgep_od.my_trigger_fcn() RETURNS trigger AS
  $BODY$
    DECLARE
      my_geom geometry(MultiPoint,%1$s);
    BEGIN
      my_geom = st_collect(NEW.situation_geometry)::geometry(MultiPoint,%1$s);
      NEW.geometry = my_geom;
      RETURN NEW;
    END;
  $BODY$
  LANGUAGE plpgsql;
$TRIGGER$, current_setting('my.srid'));
END
$DO$;

Pavel Stehule · Accepted Answer · 2018-07-05 14:04:43Z

1

You cannot to use psql variables inside any SQL string. The string is body of DO command too. You can use session variables:

\set myvar xxx
select set_config('my.myvar', :'myvar', false); 
do $$
begin
  execute format('create or replace function fx() returns void as $_$begin raise notice %L; end$_$ language plpgsql', current_setting('my.myvar')); 
end;
$$;

postgres=# \sf fx
CREATE OR REPLACE FUNCTION public.fx()
RETURNS void
LANGUAGE plpgsql
AS $function$begin raise notice 'xxx'; end$function$

Other possibility is do this replacement before psql - you can use sed

answered Jul 5, 2018 at 14:04

Pavel Stehule

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