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Re: Sequence names have 64 character limit?

From: Carlo Stonebanks <carlo(at)stonebanks(dot)ca>
To: <pgsql-general(at)postgresql(dot)org>
Subject: Re: Sequence names have 64 character limit?
Date: 2011-03-31 23:04:37
Message-ID: BLU0-SMTP90F4B7064802A0A69D7670B1BF0@phx.gbl (view raw or flat)
Thread:
Lists: pgsql-general
Once more, thanks!

Of course, using SERIAL is the ideal method, but I can't have the programs
in question fail because someone neglected to set up a dependency. Other
people may be slobs, but I'm afraid I can't be. In fact, my very first
attempt to use pg_get_serial_sequence(table_name, column_name) returned a
NULL result, which tells me that it's a reality I have to deal with.

I'll stick with the column default parsing method...

Adrian, Jerry - thanks very much for the info.

Carlo



-----Original Message-----
From: Adrian Klaver [mailto:adrian(dot)klaver(at)gmail(dot)com] 
Sent: March 31, 2011 6:15 PM
To: Carlo Stonebanks
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: [GENERAL] Sequence names have 64 character limit?

On 03/31/2011 02:47 PM, Carlo Stonebanks wrote:
> Thanks Adrian and Jerry.
>
> Technically, the best way to know which sequence a column is dependent on
is
> to actually query for it. I have functions which query
> information_schema.columns and run a regex_replace to extract the sequence
> name from the defaulting nextval() expression. This is better than
demanding
> that sequence names are predictable, but I wonder if there isn't a better
> query to run that doesn't require parsing texts? Obviously PG knows about
> the sequence's relation, probably via a dependency that finds it by
> rendering the text to regclass to an OID... but this stuff makes me
nervous.
>
> So, a query that returns the sequence name (as text, you can cast to
> regclass!) associated with a particular column, that would return NUL if
> there was none... I don't suppose anyone has written such a query
before...?
>
> Yes, I'd write a function around it!
>
> Thanks again,
>
> Carlo

Well in 8.2+ for sequences created by the SERIAL datatype there is the 
function:
pg_get_serial_sequence(table_name, column_name)

The benefit of using SERIAL is that it sets up a dependency.
If you specify the sequence via CREATE SEQUENCE then AFAIK you are left 
looking up the default and parsing it.

-- 
Adrian Klaver
adrian(dot)klaver(at)gmail(dot)com


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