Postgresql – Function/procedure to use dblink to fetch remote data and insert to multiple local tables

functionspostgresqlstored-procedures

Am trying to fetch data from remote db and insert into three local tables. Currently I have a query which is successfully getting the data into one table.

But now I was thinking of creating a function to do the whole procedure including inserting the data into the three tables. I guess am stuck here…

Best Answer

You could use a data-modifying CTE (introduced with PostgreSQL 9.1) for that to perform well. Consider the following demo:

CREATE OR REPLACE FUNCTION f_fetch3()
  RETURNS text AS
$func$

SELECT public.dblink_connect(
      'hostaddr=?.?.?.? port=5432 dbname=db user=postgres password=???');

-- Truncate tables first?
-- TRUNCATE tbl1, tbl2, tbl3;

WITH i AS (
    SELECT *
    FROM public.dblink(
        'SELECT id
               ,col1
               ,col2
               ,col3
        FROM    remote_tbl'
         ) AS d (id int, col1 text, col2 text, col3 text)
    )
    , x AS (
    INSERT INTO tbl1
    SELECT id, col1
    FROM   i
    )
    , y AS (
    INSERT INTO tbl2
    SELECT id, col2
    FROM   i
    )
INSERT INTO tbl3
SELECT id, col3
FROM   i;

/* -- Analyze tables?
ANALYZE tbl1;
ANALYZE tbl2;
ANALYZE tbl3;
*/

SELECT public.dblink_disconnect();

$func$ LANGUAGE sql VOLATILE SECURITY DEFINER
SET search_path=myschema, pg_temp;

ALTER FUNCTION f_fetch3() OWNER TO postgres;
REVOKE ALL ON FUNCTION f_fetch3() FROM public;

Call:

SELECT f_fetch3();

Tested with PostgreSQL 9.1.4.

If you put your password here, I would create that function in a separate schema and remove all access from schema and function from the general public.

You obviously have dblink installed, but for the general public: the extension has to be installed once per database:

CREATE EXTENSION dblink;
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