Re: gaussian distribution pgbench
От | Fabien COELHO |
---|---|
Тема | Re: gaussian distribution pgbench |
Дата | |
Msg-id | alpine.DEB.2.10.1404011107220.2557@sto обсуждение исходный текст |
Ответ на | Re: gaussian distribution pgbench (KONDO Mitsumasa <kondo.mitsumasa@lab.ntt.co.jp>) |
Список | pgsql-hackers |
Please find attached an updated version "v13" for this patch. I have (I hope) significanlty improved the documentation, including not so helpful mathematical explanation about the actual meaning of the threshold value. If a native English speaker could check the documentation, it would be nice! I have improved the implementation of the exponential distribution so as to avoid a loop, which allows to lift the minimum threshold value constraint, and the exponential pgbench summary displays decile and first/last percent drawing probabilities. However, the same simplification cannot be applied on the gaussian distribution part which must rely on a loop, thus needs a minimal threshold for performance. I have also checked (see the 4 attached scripts) the actual distribution against the computed probabilities. I disagree with the suggestion to remove the included gaussian & exponential tests variants, because (1) it would mean removing the specific summaries as well, which are essential to help feel how the feature works; (2) the corresponding code in the source is rather straightforward; (3) the tests correspond to the schema and data created with -i, so it makes sense that they are stored in pgbench; (4) in order for this feature to be used, it is best that it is available directly and simply from pgbench, and not to be thought for elsewhere. If this is a commit blocker, then the embedded script will have to be removed, but I really think that they add a significant value to pgbench and its "non uniform" features because they make it easy to test. If Mitsumasa-san aggrees with these proposed changes, I would suggest to apply this patch. -- Fabien
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