Re: Best free tool for relationship extraction

From: Alexander Gataric [mailto:gataric(at)usa(dot)net]
Sent: Thursday, September 13, 2012 12:52 PM
To: pgsql-general(at)postgresql(dot)org
Subject: Best free tool for relationship extraction

I need to determine relationships between several tables. Is there a free tool to extract these from catalog tables? Is there an SQL that also does this?

Thanks
Alex

Try this SQL:

WITH RECURSIVE FK_recursive(distance, child_table, parent_table, FK_constraint_name, unique_constraint_name,
ON_DELETE, ON_UPDATE, is_deferrable, FK_path) AS (
SELECT 1, tc.table_name, ctu.table_name, ctu.constraint_name, rc.unique_constraint_name,
rc.delete_rule, rc.update_rule, tc.is_deferrable, quote_ident(ctu.table_name)
FROM information_schema.constraint_table_usage ctu, information_schema.table_constraints tc, information_schema.referential_constraints rc
WHERE ctu.table_name = 'gp_part_space' and ctu.table_catalog = 'vector'
and tc.constraint_name = ctu.constraint_name and tc.constraint_type = 'FOREIGN KEY' and tc.constraint_catalog = 'vector'
and ctu.constraint_name = rc.constraint_name
UNION ALL
SELECT er.distance + 1, tc.table_name, ctu.table_name, ctu.constraint_name, rc.unique_constraint_name,
rc.delete_rule, rc.update_rule, tc.is_deferrable, er.FK_path || ' <- ' || quote_ident(ctu.table_name)
FROM FK_recursive er, information_schema.constraint_table_usage ctu, information_schema.table_constraints tc, information_schema.referential_constraints rc
WHERE er.child_table = ctu.table_name and ctu.table_catalog = 'vector'
and tc.constraint_name = ctu.constraint_name and tc.constraint_type = 'FOREIGN KEY' and tc.constraint_catalog = 'vector'
and ctu.constraint_name = rc.constraint_name
)
SELECT distance, child_table, parent_table, FK_constraint_name, unique_constraint_name,
ON_DELETE, ON_UPDATE, is_deferrable, FK_path || ' <- ' || quote_ident(child_table) AS FK_path
FROM FK_recursive ORDER BY distance, parent_table;

If you get an error like this (possible on 8.4.5):

ERROR: operator is not unique: smallint[] <@ smallint[]
LINE 1: select $1 <@ $2 and $2 <@ $1
^
HINT: Could not choose a best candidate operator. You might need to add explicit type casts.
QUERY: select $1 <@ $2 and $2 <@ $1
CONTEXT: SQL function "_pg_keysequal" during inlining

Then recompile the function:

SET search_path TO information_schema;
CREATE OR REPLACE FUNCTION _pg_keysequal(smallint[], smallint[]) RETURNS boolean
LANGUAGE sql IMMUTABLE
AS 'select $1 operator(pg_catalog.<@) $2 and $2 operator(pg_catalog.<@) $1';
SET search_path TO public;

And then re-run original recursive query.

Regards,
Igor Neyman