On 2010-10-28 15:13, Merlin Moncure wrote:
> On Wed, Oct 27, 2010 at 3:47 PM, Jesper Krogh<jesper(at)krogh(dot)cc> wrote:
>> On 2010-10-27 20:51, Merlin Moncure wrote:
>>>> Yes, I am quite aware of how the o/s page cache works. All else being
>>>> equal, I more compact database obviously would be preferred. However
>>>> 'all else' is not necessarily equal. I can mount my database on bzip
>>>> volume, that must make it faster, right? wrong. I understand the
>>>> postgres storage architecture pretty well, and the low hanging fruit
>>>> having been grabbed further layout compression is only going to come
>>>> as a result of tradeoffs.
>> Or configureabillity.. Not directly related to overall space consumption
>> but I have been working on a patch that would make TOAST* kick in
>> earlier in the process, giving a "slimmer" main table with visibillity
>> and simple columns and moving larger colums more aggressively to TOAST.
> Do you have any benchmarks supporting if/when such a change would be beneficial?
On, IO-bound queries it pretty much translates to the ration between
the toast-table-size vs. the main-table-size.
Trying to aggressively speed up "select count(*) from table" gives this:
with shutdown of pg and drop caches inbetween... the "default" select
count (*) on 50K tuples
gives 4.613ms (2 tuples pr page) vs. 318ms... (8 tuples pr page).
PG default is inbetween...
In response to
pgsql-performance by date
|Next:||From: Cédric Villemain||Date: 2010-10-28 15:31:29|
|Subject: Re: How does PG know if data is in memory?|
|Previous:||From: Mladen Gogala||Date: 2010-10-28 15:23:13|
|Subject: Re: Slow Query- Simple taking|
pgsql-hackers by date
|Next:||From: Tom Lane||Date: 2010-10-28 15:39:11|
|Subject: Re: plperl arginfo |
|Previous:||From: Andrew Dunstan||Date: 2010-10-28 15:24:50|
|Subject: plperl arginfo|