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Re: Slow table update - SOLVED!


  • From: Laszlo Nagy <gandalf(at)shopzeus(dot)com>
  • To: Gregory Williamson <Gregory(dot)Williamson(at)digitalglobe(dot)com>
  • Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-performance(at)postgresql(dot)org, Daniel Fekete <danieleff(at)gmail(dot)com>
  • Subject: Re: Slow table update - SOLVED!
  • Date: Mon, 29 Dec 2008 14:11:48 +0100
  • Message-id: <4958CC94.6020103@shopzeus.com> <text/plain>



Inf 8.3 the HOT feature may help if the columns being updated are indexed ... what version of PostgreSQL is this again ? (Forgive my lack of memory -- the last few days I've forgotten a lot, heh heh.)

8.3.5.

The colum that was being updated is part of one small index only.


Any chances to reduce those to a bare minimum, perhaps using conditional index strategies or even some form of replication, so the primary uses indexes related to the updates and the mirror uses indexes related to the read-only / reporting needs ? Perhaps some form of staging table with no indexes to load, check data, etc. and then insert.

Any way to reduce those ? Check the usage via the system stats on table/index use and try removing some and testing to see what makes a difference.

We tried to remove all indexes on a test system and the update was speedy. We are going to try to reduce the row size also move static description/name/textual data into a separate table, and leave frequently updated data in the original one. We tested this theoretical version:

Query returned successfully: 182752 rows affected, 56885 ms execution time.

This is much faster. However, this table is used by hundreds of programs. Anyway, I got the answer to my question.

Thank you!

  Laszlo




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