Re: unexpected psql "feature"
От | Fabien COELHO |
---|---|
Тема | Re: unexpected psql "feature" |
Дата | |
Msg-id | alpine.DEB.2.20.1607141007420.1962@sto обсуждение исходный текст |
Ответ на | Re: unexpected psql "feature" (Fabien COELHO <coelho@cri.ensmp.fr>) |
Список | pgsql-hackers |
> Consider a throttled read-only load composed of 3 random selects, > several rounds (so.sql) vs one (so2.sql): > > > pgbench -h server -T 100 -P 1 --rate 200 -c 2 -f so.sql -f so2.sql > SQL script 1: so.sql > - latency average = 1.878 ms > SQL script 2: so2.sql > - latency average = 1.089 ms > > There is 0.8 ms latency reduction, that is a 40% difference. Standard > deviation is also significantly lower. More fun with these two scripts, for those who focus on tps. > pgbench -h server -M prepared -T 10 -P 1 -c 8 -f so.sql ... latency average = 1.128 ms latency stddev = 0.167 ms tps =7024.818252 (including connections establishing) > pgbench -h server -T 10 -P 1 -c 8 -f so2.sql # cannot do "-M prepared" on multiple commands... anyway: ... latency average= 0.454 ms latency stddev = 0.110 ms tps = 17317.807554 (including connections establishing) A mere 2.46 speedup for the read-only load. The same with a "simple update" pgbench load, not compound & prepared: latency average = 1.716 ms latency stddev = 1.890 ms tps = 4623.270608 (including connections establishing) vs compound but not prepared: latency average = 1.294 ms latency stddev = 0.870 ms tps = 6122.289249 (including connections establishing) Ok, it is less impressive, just 30% better. -- Fabien.
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