On Thu, Nov 27, 2008 at 05:15:04PM -0500, Robert Haas wrote: > A random thought: maybe the reason I'm not seeing any benefit is > because my tables are just too small - most contain at most a few > thousand rows, and some are much smaller. Maybe > default_statistics_target should vary with the table size? Something > like, 0.1% of the rows to a maximum of 100... and then 0.01% of the > rows after that to some higher maximum.... but always a minimum of at > least 10. I'm guessing that people with really big tables are less > likely to mind longer planning times and more likely to benefit from > finding better plans...
Something like this makes an awful lot of sense to me. A higher statistics target (in theory) better captures the fine details of a distribution of values; tables with fewer rows are unlikely to demonstrate fine details (as are tables with categorical, as opposed to continuous, values). Returning to the original topic of a configuration creator, perhaps such a tool should ask the user how big (s)he expects the tables to grow, or perhaps it should be able to investigate a particular column and recommend a statistics target based on its distribution, size, etc. - Josh / eggyknap
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