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Re: select max(field) from table much faster with a group by clause?
- From: Gregory Stark <stark(at)enterprisedb(dot)com>
- To: "Palle Girgensohn" <girgen(at)pingpong(dot)net>
- Cc: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, <pgsql-performance(at)postgresql(dot)org>
- Subject: Re: select max(field) from table much faster with a group by clause?
- Date: Thu, 01 Nov 2007 15:47:32 +0000
"Palle Girgensohn" <girgen(at)pingpong(dot)net> writes: > Are there any other things I can modify? You might consider an index on <userid,when>. Keep in mind that every new index imposes an incremental cost on every update and insert and increases the time for vacuum. > max_prepared_transactions = 100 # can be 0 or more Are you actually using prepared transactions (are you synchronising multiple databases using a transaction manager)? If not then set this to 0 as it takes some resources. > maintenance_work_mem = 16384 # min 1024, size in KB Raising this might decrease vacuum times if that's a problem. > fsync = off You realize that this means if the system loses power or the kernel crashes you could have data corruption? Do you take very frequent backups or can you reconstruct your data? -- Gregory Stark EnterpriseDB http://www.enterprisedb.com Ask me about EnterpriseDB's Slony Replication support!
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- select max(field) from table much faster with a group by clause?
- From: Palle Girgensohn
- Re: select max(field) from table much faster with a group by clause?
- From: Tom Lane
- Re: select max(field) from table much faster with a group by clause?
- From: Palle Girgensohn
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