Re: Performance Improvement by reducing WAL for Update Operation

On Wed, Jan 15, 2014 at 7:28 AM, Amit Kapila <amit.kapila16@gmail.com> wrote:
> Unpatched
> -------------------
>                 testname                             | wal_generated |
>     duration
> ----------------------------------------------------------+----------------------+------------------
>  one short and one long field, no change |    1054923224 |  33.101135969162
>
> After pgrb_delta_encoding_v4
> ---------------------------------------------
>
>                 testname                             | wal_generated |
>     duration
> ----------------------------------------------------------+----------------------+------------------
>  one short and one long field, no change |     877859144 | 30.6749138832092
>
>
> Temporary Changes
> (Revert Max Chunksize = 4 and logic of finding longer match)
> ---------------------------------------------------------------------------------------------
>
>                  testname                            | wal_generated |
>     duration
> ----------------------------------------------------------+----------------------+------------------
>  one short and one long field, no change |     677337304 | 25.4048750400543

Sure, but watch me not care.

If we're interested in taking advantage of the internal
compressibility of tuples, we can do a lot better than this patch.  We
can compress the old tuple and the new tuple.  We can compress
full-page images.  We can compress inserted tuples.  But that's not
the point of this patch.

The point of *this* patch is to exploit the fact that the old and new
tuples are likely to be very similar, NOT to squeeze out every ounce
of compression from other sources.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company