Nathan Boley presents:
Statistics and Postgres - How the planner sees your data.
Postgres relies heavily on statistics collected from data tables to
execute queries in the most efficient way possible. Despite the
relative simplicity of these statistics, the actual process by which
they are collected and used to generate plans is a bit enigmatic. In
the next 50 minutes, I will go through the assumptions that the
planner makes about data access patterns, the heuristics that generate
and apply the summary statistics, and a theorem from probability
theory that is central to the planner's estimates. Finally, if time
permits, I will show how a custom selectivity function can
dramatically improve the planner accuracy for odd data distributions.
My hope is that a clear understanding of the process by which Postgres
collects and applies statistics will remove some of the black magic
from tuning Postgres and spur the development of better analysis
This meeting will also be streamed live on the web at
Remote people can ask questions there or in
Pizza from The Cheeseboard contributed by Continuent. RSVP to get a slice!