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I have a few questions re. PostgreSQL.

  1. What is the sweet spot so far as number of CPU cores goes?
  2. Does anyone know when parallel queries will be implemented?
  3. WRT #2, I've seen benchmarks where PostgreSQL beats SQL Server. What is the real implications of not having parallel queries?

Thanks.

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In the future, one question per question please. –  Peter Eisentraut Jan 7 '11 at 8:32

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up vote 2 down vote accepted
  1. If you have a lot of contention, there is some anecdotal evidence that performance doesn't get better or degrades after about 32 CPU cores. It is difficult to get definitive results in that area, though. If someone knew the answer, they would probably also be able to fix the problem. If you think your application will be pushing the limits on this, I suggest running tests yourself. pgbench might help you get started.

  2. It doesn't look as though it will happen anytime soon. Don't plan on it.

  3. This is highly dependent on what you are doing. If you have an OLTP application with lots of concurrent clients, it won't matter much. If you have more of an OLAP style usage, then it will suck because you might only be using one or two out of many CPUs, and especially your sorts could conceivably be faster.

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thanks. When you say 32 CPUs, do you mean 32 cores? –  IanC Jan 7 '11 at 9:33
    
Yes, I edited the answer to that effect. –  Peter Eisentraut Jan 7 '11 at 9:36
    
Did you ever experiment with hyperthreading? I've read it's better to have it off. –  IanC Jan 7 '11 at 9:48
    
That is my understanding as well, but it's been a while since I have investigated it. Hardware has changed a lot since then. –  Peter Eisentraut Jan 7 '11 at 11:07
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Thanks... I'll post as a question & see what comes up. –  IanC Jan 7 '11 at 11:09

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