Thread: Recursive CTE in function problem

Postgres 9.4.1, with these tables:

grpl_collection.collections
  id     | integer |
  name   | text    |
  parent | bigint  |
(An adjacency list representing a collections hierarchy)

grpl_collection.collections_copy_map
  id         | integer |
  collection | bigint  |
  copy       | bigint  |
(map a copy to the collections it belongs to)

This query correctly answers if a copy is in a collection tree:

  select 3006377 in (select copy from
grpl_collection.collections_copy_map where copy=3006377 and collection in
(WITH    RECURSIVE
         q AS
         (
         SELECT  c.id
         FROM    grpl_collection.collections c
         WHERE   name=$$Movies$$
         UNION ALL
         SELECT  cn.id
         FROM    q
         JOIN    grpl_collection.collections cn
         ON      cn.parent = q.id
         )
SELECT  id
FROM    q));


But when I use it as a function it always returns false:

CREATE OR REPLACE FUNCTION grpl_collection.copy_in_collection_name(cpid
bigint, colname text)
  RETURNS boolean
  LANGUAGE plpgsql
AS $function$
BEGIN
     RETURN cpid in (select copy from
grpl_collection.collections_copy_map where copy=cpid and collection in
(WITH    RECURSIVE
         q AS
         (
         SELECT  c.id
         FROM    grpl_collection.collections c
         WHERE   name=$$colname$$
         UNION
         SELECT  cn.id
         FROM    q
         JOIN    grpl_collection.collections cn
         ON      cn.parent = q.id
         )
SELECT id FROM q ));
END;
$function$

What am I missing?

On Thu, Feb 4, 2016 at 12:37 PM, Doug Kyle <dkyle@grpl.org> wrote:

But when I use it as a function it always returns false:

CREATE OR REPLACE FUNCTION grpl_collection.copy_in_collection_name(cpid bigint, colname text)
 RETURNS boolean
 LANGUAGE plpgsql
AS $function$
BEGIN
    RETURN cpid in (select copy from grpl_collection.collections_copy_map where copy=cpid and collection in
(WITH    RECURSIVE
        q AS
        (
        SELECT  c.id
        FROM    grpl_collection.collections c
        WHERE   name=$$colname$$

​      <<<------------​

        UNION
        SELECT  cn.id
        FROM    q
        JOIN    grpl_collection.collections cn
        ON      cn.parent = q.id
        )
SELECT id FROM q ));
END;
$function$

​ $$colname$$ is a string whose contents is the literal 'colname'​, not the function argument named colname as you seem to want.

David J.