diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/optimizer/geqo/pg_geqo.sample | 26 |
1 files changed, 17 insertions, 9 deletions
diff --git a/src/backend/optimizer/geqo/pg_geqo.sample b/src/backend/optimizer/geqo/pg_geqo.sample index 12694e3e4dc..1f704a44e8b 100644 --- a/src/backend/optimizer/geqo/pg_geqo.sample +++ b/src/backend/optimizer/geqo/pg_geqo.sample @@ -12,27 +12,30 @@ # utesch@aut.tu-freiberg.de * Freiberg, Germany * #*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*= -# this file should be '$PGDATA/pg_geqo', but it doesn't have -# to exist +# To make this file do something, copy it to '$PGDATA/pg_geqo' +# and edit parameters to taste. +# If '$PGDATA/pg_geqo' doesn't exist, the system will use default parameters. +# The file is re-read for every GEQO optimization, if it does exist. # comment character is '#' # # separator between recognized tag and possible value # must be white space -# qs: means query size, which is the number of relations +# QS: means query size, which is the number of relations # contained in a query #=================+===================+=============================+ # RECOGNIZED TAGS | POSSIBLE VALUES | DEFAULTS | #=================+===================+=============================+ -# 'Pool_Size' | positive int | 2^(qs+1) | +# 'Pool_Size' | positive int | 2^(QS+1), but not less than | +# | | 128 nor more than 1024. | #-----------------+-------------------+-----------------------------+ # 'Effort' | [low,medium,high] | medium | #-----------------+-------------------+-----------------------------+ -# 'Generations' | positive int | 'Effort' * log2('Pool_Size')| +# 'Generations' | positive int | Effort * log2(Pool_Size) | #-----------------+-------------------+-----------------------------+ -# 'Selection_Bias'| [1.50; 2.00] | 2.0 | +# 'Selection_Bias'| [1.50 .. 2.00] | 2.0 | #-----------------+-------------------+-----------------------------+ # 'Random_Seed' | positive long | time(NULL) | #=================+===================+=============================+ @@ -41,15 +44,20 @@ # It gives us the number of individuals within one population. # # 'Effort' 'low' means integer value of 1, 'medium' 40, and 'high' 80. +# Note: Effort is *only* used to derive a default value for Generations +# --- if you specify Generations then Effort does not matter. # -# 'Generations' gives us the stopping criterion for the number -# of iterations within the genetic algorithm. +# 'Generations' specifies the number of iterations in the genetic algorithm. +# +# GEQO runtime is roughly proportional to Pool_Size + Generations. # # 'Selection_Bias' gives us the selective pressure within the # population. # # 'Random_Seed' is the random seed for the random() function. -# You don't have to set it. +# You don't have to set it. If you do set it, then successive GEQO +# runs will produce repeatable results, whereas if you don't set it +# there will be some randomness in the results... # All parameters will be computed within the GEQO module when they # are not set in the pg_geqo file. |