Just theoretically assumption. PostgreSQL sometimes may optimise internal format of data and can sometimes zip data.
ASCIIdata can be zipped better, then binary random data. Also PostgreSQL sometimes take decision to keep a column in an
externalfile, if the column is still too big after zip. I don’t know what exactly happens in your case, but here can be
areason.
> 18 марта 2019 г., в 17:33, Thomas Güttler <guettliml@thomas-guettler.de> написал(а):
>
> I did some benchmarking and in my setup there was major
> performance difference.
>
> I tested a ByteA column.
>
> If I used ascii data the tests took 52 seconds.
> If I used random binary data the test took 250 seconds.
>
> binary data is (roughly) five times slower than ascii data?
>
> Is this a know fact, or is there something wrong with my benchmark?
>
> I used Python and psycopg2.
>
> Regards,
> Thomas Güttler
>
>
> --
> Thomas Guettler http://www.thomas-guettler.de/
> I am looking for feedback: https://github.com/guettli/programming-guidelines
>