On 2019-03-20 13:20:57 +0100, Thomas Güttler wrote: > > > Am 19.03.19 um 20:37 schrieb Peter J. Holzer: > > On 2019-03-18 15:33:17 +0100, Thomas Güttler wrote: > > > 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. > > > > I don't see this here (Debian 9, Python 3,5, psycopg2 2.7.6, PostgreSQL > > 9.5). > > > > I modified my bench-bytea script (https://github.com/hjp/blob-bench) to > > restrict the byte values to printable ASCII (32 .. 126). There was > > absolutely no difference, as the attached graph shows. > > Strange. I saw a big difference. > What did you test? > I tested inserts. The graph with the quantiles was for selects. For inserts I made only a scatterplot and there didn't seem to be any difference either. I'll check the quantiles, too, but I expect to see at most a small difference. A large difference as the one you saw would show up clearly in a scatterplot, too. My test ist in github (see URL above). Do see the same difference with my test on your system? hp -- _ | Peter J. Holzer | we build much bigger, better disasters now |_|_) | | because we have much more sophisticated | | | hjp@xxxxxx | management tools. __/ | http://www.hjp.at/ | -- Ross Anderson <https://www.edge.org/>
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