CODEWITHSUNDEEP
sqlpostgresqlplpgsql
WeakLearner
WeakLearner

Reputation: 938

dynamic portion of plpgsql function

I have a function that loops through all points and compares them to other points (yes i know this doesn't need to be done in plpgsql - this is a toy MWE). The function returns the points with the largest x coordinate:

create type point as (x integer, y integer);
create or replace function test() returns set of Point as
$$
declare
    p1 point;
    p2 point;
    bool integer;
begin
for p1 in select * from table loop
    bool := 0;
    for p2 in select * from table loop
        if p2.x > p1.x then bool :=1;
        exit;
        end if;
    end loop;
    if bool = 0 then return next p1;
    end if;
end loop;
end;
$$ language 'plpgsql';

which works. What I want to do is be able to have the table name as a parameter of the function, I am confused as to where to put the execute statement.

Upvotes: 3

Views: 72

Answers (1)

Vao Tsun
Vao Tsun

Reputation: 51659

https://www.postgresql.org/docs/current/static/plpgsql-control-structures.html:

The FOR-IN-EXECUTE statement is another way to iterate over rows:

t=# do
$$
declare
  _t text := 'pg_tables';
  _r record;
begin
  for _r in execute format('select * from %I limit 4',_t) loop
    raise info '%',_r.tablename;
  end loop;
end;
$$
;
INFO:  s141
INFO:  events
INFO:  tg_rep_que
INFO:  t4
DO

Upvotes: 6

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