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README.pg_autovacuum	34	6

*** README.pg_autovacuum.orig	Thu Nov 20 19:58:29 2003
--- README.pg_autovacuum	Thu Nov 20 20:35:34 2003
***************
*** 141,163 ****
  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:
!     vacuum_base_value + (vacuum_scaling_factor * "number of tuples in the table")
! 
  AnalyzeThreshold is equal to:
!     analyze_base_value + (analyze_scaling_factor * "number of tuples in the table")
! 
  The AnalyzeThreshold defaults to half of the VacuumThreshold since it
  represents a much less expensive operation (approx 5%-10% of vacuum),
  and running ANALYZE more often should not substantially degrade system
  performance.
  
  Sleeping:
  ---------
  
--- 141,191 ----
  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:
!     vacuum_base_value + (vacuum_scaling_factor * "number of tuples in the 
! table")
  AnalyzeThreshold is equal to:
!     analyze_base_value + (analyze_scaling_factor * "number of tuples in the 
! table")
  The AnalyzeThreshold defaults to half of the VacuumThreshold since it
  represents a much less expensive operation (approx 5%-10% of vacuum),
  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.
+ 
+ Base		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 
+ thatsuch installation tune their analyze threshold separately, rather than 
+ relying upon the default behaviour.
+ 
+ Furthermore, for aggressive vacuum/analyze behaviour, it is recommended that
+ scaling factor is set to less than 1. However too aggresive operation can affect
+ performance of normal database operations adversely. Do not apply such setting
+ to production databases without prior testing.
+ 
  Sleeping:
  ---------