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

On 10/29/23 09:45, pf(at)pfortin(dot)com wrote:
> On Sun, 29 Oct 2023 16:16:05 +0100 Peter J. Holzer wrote:
>
>> On 2023-10-29 09:21:46 -0400, pf(at)pfortin(dot)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(dot)klaver(at)aklaver(dot)com