Re: [SOLVED?] Re: Disk wait problem... not hardware...

On 10/29/23 09:45, pf@pfortin.com wrote:
> On Sun, 29 Oct 2023 16:16:05 +0100 Peter J. Holzer wrote:
> 
>> On 2023-10-29 09:21:46 -0400, pf@pfortin.com wrote:
>>> These are all static tables. Does PG maintain a table row count so as to
>>> avoid having to count each time?
>>
>> No. To count the rows in a table, Postgres has to actually read the
>> whole table (or an index, if a suitable index (e.g. a primary key)
>> exists).
> 
> Am I correct to assume count(fieldname) would only load that column for
> counting?  In other words: we should be specific (avoid "*") in general?

Read:

https://wiki.postgresql.org/wiki/Slow_Counting


>>> WB is setup to:
>>> * autoload table row count
>>> * autoload table data (restricted with LIMIT)
>>
>> Maybe WB can be set up to get n_live_tup instead of the real row count?

So basically you are dealing with a client issue.

> 
> It appears this is hard-coded [on/off only]; but I thought I saw the WB
> author post on this list recently...
> 
>>         hp
>>
> 
> 

-- 
Adrian Klaver
adrian.klaver@aklaver.com