Re: Foreign key columns

On Thu, Nov 5, 2009 at 2:08 PM, Svenne Krap <svenne.lists@krap.dk> wrote:
> Hi.
>
> Is there a simple way to get foreign key data... for example I found a
> view, that does what I want ...
>
> It delivers
>
>   fk_table   |     fk_column      |     pk_table      | pk_column |           constraint_name
>
> --------------+--------------------+-------------------+-----------+--------------------------------------
>
>  organisation | customer_rep       | person            | id        | organisation_customer_rep_fkey
>
>  organisation | ekstra_skema       | ekstra_skema      | id        | org_schema_fkey
>
>  organisation | in_group           | organisation      | id        | organisation_in_group_fkey
>
>  organisation | org_paying_company | organisation      | id        | organisation_org_paying_company_fkey
>
>  organisation | primary_contact    | person            | id        | primary_contact_fkey
>
>  organisation | type               | organisation_type | id        | organisation_type_fkey
>
>
>
> The query in question is
>
> SELECT FK.TABLE_NAME as FK_Table, CU.COLUMN_NAME as FK_Column,
> PK.TABLE_NAME as PK_Table, PT.COLUMN_NAME as PK_Column,
> C.CONSTRAINT_NAME as Constraint_Name
> FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS C
> INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS FK ON C.CONSTRAINT_NAME
> = FK.CONSTRAINT_NAME
> INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS PK ON
> C.UNIQUE_CONSTRAINT_NAME = PK.CONSTRAINT_NAME
> INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE CU ON C.CONSTRAINT_NAME =
> CU.CONSTRAINT_NAME
> INNER JOIN (
>     SELECT i1.TABLE_NAME, i2.COLUMN_NAME FROM
> INFORMATION_SCHEMA.TABLE_CONSTRAINTS i1
>        INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE i2 ON
> i1.CONSTRAINT_NAME = i2.CONSTRAINT_NAME
>        WHERE i1.CONSTRAINT_TYPE = 'PRIMARY KEY') PT ON PT.TABLE_NAME =
> PK.TABLE_NAME WHERE FK.TABLE_NAME='organisation' ORDER BY 1,2,3,4;
>
>
> The only problem is that this query is sloooooow, runs in tens of seconds...

It runs in 112 milliseconds on my machine.  Maybe your catalogs are
extremely bloated?

> Is there a good native (i.e. fast) pgsql-query to find that type of
> information?

This one seems to work pretty well.  If you want to see a query to
find such things, the easy way is to start psql with the -E switch,
and issue a \d command on the organisation table and steal the SQL
from there.  That query will be pgsql specific, and possibly / likely
pgsql VERSION dependent, so know that going into it.