Re: Table checksum proposal

On Thu, Jul 24, 2014 at 01:43:29PM +0200, hubert depesz lubaczewski wrote:

> > 1. Should this be a contrib module which provides a function, or should it
> > be a built-in piece of functionality?
> > 2. Is MD5 too heavyweight for this?  Would using a non-cryptographic
> > checksum be worth the speed boost?
> > 3. Is there a risk of different architectures/versions returning different
> > checksums for tables which could be considered identical?  If so, is this
> > worth worrying about?
> >
>
> Hmm - Do you really think we need an extension for something that can be
> done using query as simple as:
>
> select md5(string_agg(md5(c::text), '' order by md5(c::text))) from
> pg_class c;

Just a nitpick, and not really relevant to the OPs question,
but probably useful to people trying to actually use this
across potentially different locale settings: throw in a

    DECODE(md5(...), 'hex')

for the ORDER BY like

    select md5(string_agg(md5(c::text), '' order by decode(md5(c::text), 'hex'))) from pg_class c;

Karsten
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