Re: Inverse of pg_get_serial_sequence?

On Wed, Sep 3, 2014 at 10:44 AM, Andres Freund <andres@2ndquadrant.com> wrote:
> On 2014-09-03 09:31:50 -0400, Robert Haas wrote:
>> On Fri, Aug 29, 2014 at 1:26 PM, Andres Freund <andres@2ndquadrant.com> wrote:
>> > We have pg_get_serial_sequence() mapping (relation, colum) to the
>> > sequence. What I'm missing right now is the inverse. I.e. given a
>> > sequence tell me the owner.
>> > describe.c has a query for that, and it's not too hard to write, but it
>> > still seems 'unfriendly' not to provide it.
>> >
>> > Does anybody dislike adding a function for that?
>>
>> I'll go out on a limb and say that it sounds like pointless catalog
>> bloat to me.  I am all in favor of adding things like this where the
>> SQL query is painful to write (e.g. things involving pg_depend) but if
>> it's a simple SELECT query then, eh, not really excited about it.
>
> There's not really a simple select for it, is there? psql uses:
>
>                 /* Get the column that owns this sequence */
>                 printfPQExpBuffer(&buf, "SELECT pg_catalog.quote_ident(nspname) || '.' ||"
>                                                   "\n   pg_catalog.quote_ident(relname) || '.' ||"
>                                                   "\n   pg_catalog.quote_ident(attname)"
>                                                   "\nFROM pg_catalog.pg_class c"
>                                         "\nINNER JOIN pg_catalog.pg_depend d ON c.oid=d.refobjid"
>                          "\nINNER JOIN pg_catalog.pg_namespace n ON n.oid=c.relnamespace"
>                                                   "\nINNER JOIN pg_catalog.pg_attribute a ON ("
>                                                   "\n a.attrelid=c.oid AND"
>                                                   "\n a.attnum=d.refobjsubid)"
>                            "\nWHERE d.classid='pg_catalog.pg_class'::pg_catalog.regclass"
>                          "\n AND d.refclassid='pg_catalog.pg_class'::pg_catalog.regclass"
>                                                   "\n AND d.objid=%s"
>                                                   "\n AND d.deptype='a'",
>                                                   oid);

Oh, OK.  Yeah, that's kind of hairy.

-- 
Robert Haas
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