Re: proposal: Set effective_cache_size to greater of .conf value, shared_buffers

On 6 May 2014 22:54, Robert Haas <robertmhaas@gmail.com> wrote:
> On Tue, May 6, 2014 at 4:38 PM, Simon Riggs <simon@2ndquadrant.com> wrote:
>>  I read the code, think what to say and then say what I think, not
>> rely on dogma.
>>
>> I tried to help years ago by changing the docs on e_c_s, but that's
>> been mostly ignored down the years, as it is again here.
>
> Well, for what it's worth, I've encountered systems where setting
> effective_cache_size too low resulted in bad query plans, but I've
> never encountered the reverse situation.

I agree with that.

Though that misses my point, which is that you can't know that all of
that memory is truly available on a server with many concurrent users.
Choosing settings that undercost memory intensive plans are not the
best choice for a default strategy in a mixed workload when cache may
be better used elsewhere, even if such settings make sense for some
individual users.

-- Simon Riggs                   http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services