Re: DBI:to sort tables according to their dependencies

[erix]

Here is an example using pg_depend, a postgres catalog:

select 
        classid::regclass         as  "depender object class"
   ,
        case classid
        when 'pg_class'::regclass then objid::regclass::text
        when 'pg_type'::regclass  then objid::regtype::text
        when 'pg_proc'::regclass  then objid::regprocedure::text
        else objid::text 
        end
            as "depender object identity"
    ,
        objsubid
    ,
        refclassid::regclass as "referenced object class"
    ,
        case refclassid
        when 'pg_class'::regclass then refobjid::regclass::text
        when 'pg_type'::regclass  then refobjid::regtype::text
        when 'pg_proc'::regclass  then refobjid::regprocedure::text
        else refobjid::text
        end
            as "referenced object identity"
    ,
        refobjsubid
    ,
        case deptype
        when 'p' then 'pinned'
        when 'i' then 'internal'
        when 'a' then 'automatic'
        when 'n' then 'normal'
        end
            as "dependency type"

from pg_catalog.pg_depend 

-- exclude dependencies on system objects:
where objid >= 16384 or refobjid >= 16384 
;

That code comes from the postgresql wiki, but see also the pg_depend page, and for catalog stuff generally, internals (includes dictionary tables).

[wrog]

As I understand it, pg_depend contains all links between all database objects (tables, columns, sequences, indexes, blobs, etc...); it gets used by the server to decide what all goes away when you do DROP TABLE/whatever. There may be Rather a Lot of Filtering to do to get it down to just foreign-key links between tables.

An alternative would be to start from the list of constraints in pg_constraint (link is for version 8.4; adjust accordingly if you're using some other version of postgresql)