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README.pg_autovacuum	25	2

*** README.pg_autovacuum.orig	Thu Nov 20 19:58:29 2003
--- README.pg_autovacuum	Thu Nov 20 20:26:39 2003
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*** 141,150 ****
  depending on the mixture of table activity (insert, update, or
  delete):
  
! - If the number of (inserts + updates + deletes) > AnalyzeThreshold, then
    only an analyze is performed.
  
! - If the number of (deletes + updates) > VacuumThreshold, then a
    vacuum analyze is performed.
  
  VacuumThreshold is equal to:
--- 141,150 ----
  depending on the mixture of table activity (insert, update, or
  delete):
  
! - If the number of (inserts + updates + deletes) >= AnalyzeThreshold, then
    only an analyze is performed.
  
! - If the number of (deletes + updates) >= VacuumThreshold, then a
    vacuum analyze is performed.
  
  VacuumThreshold is equal to:
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*** 158,163 ****
--- 158,186 ----
  and running ANALYZE more often should not substantially degrade system
  performance.
  
+ Examples:
+ 
+ Following table shows typical usage of pg_autovacuum settings.
+ These are put here so that a DBA can have some starting point while
+ tuning pg_autovacuum.
+ 
+ Vacuum is triggered by updates and deletes. So in case of vacuum,
+ last column indicates total of updates and deletes required
+ to trigger vacuum. In case of analyze, the operations would count total
+ number of inserts, updates and deletes.
+ 
+ Threshold	Scaling factor	Records		No. of Operations
+ 1,000		1		10,000		11,000
+ 1,000		2		10,000		21,000
+ 1,000		0.5		10,000		 6,000
+ 1,000		0.1		10,000		 2,000
+ 
+ Although analyze is cheaper operation compared to vacuum,
+ it might be needed less often. The default is to analyze twice as much as
+ vacuum but that might be too aggressive for some installations. It is advised that
+ such installation tune their analyze threshold separately, rather than relying upon
+ the default behaviour.
+ 
  Sleeping:
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