Re: Script which shows performance of ByteA: ascii vs binary

On 3/22/19 6:04 AM, Thomas Güttler wrote:
>
>
> Am 22.03.19 um 13:40 schrieb Francisco Olarte:
>> Thomas:
>>
>> On Fri, Mar 22, 2019 at 11:22 AM Thomas Güttler
>> <guettliml(at)thomas-guettler(dot)de> wrote:
>>> Thank you for asking several times for a benchmark.
>>> I wrote it now and it is visible: inserting random bytes into bytea
>>> is much slower,
>>> if you use the psycopg2 defaults.
>>> Here is the chart:
>>>
>>> https://github.com/guettli/misc/blob/master/bench-bytea-inserts-postrgres.png
>>>
>>> And here is the script which creates the chart:
>>>
>>> https://github.com/guettli/misc/blob/master/bench-bytea-inserts-postrgres.py
>>>
>>
>> I'm not too sure, but I read ( in the code ) you are measuring a
>> nearly not compressible urandom data againtst a highly compressible (
>> 'x'*i ) data,
>> are you sure the difference is not due to data being compressed and
>> generating much less disk usage in toast-tables/wal?
>
> +1
>
> for this case toast-tables/wal is a detail of the implementation.
> This tests does not care about the "why it takes longer". It just generates
> a performance chart.

TOAST is tunable, might want to take a look at:

https://www.postgresql.org/docs/11/storage-toast.html

>
> Yes, it does exactly what you say: it compares
> nearly not compressible urandom data against a highly compressible data.
>
> In my case, will get nearly random data (binary PDF, JPG, ...). And
> that's why
> I wanted to benchmark it.
>
> Regards,
>   Thomas
>
>

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com