Stefan Kaltenbrunner <[EMAIL PROTECTED]> writes: > Tom Lane wrote: >> The big problem there seems to be the drastic misestimation of the >> number of rows matching the p_name ~~ '%ghost%' condition. What does >> pg_stats have for the p_name column?
> http://www.kaltenbrunner.cc/files/pg_stat_p_name.txt Hmm ... pattern_sel already applies the operator directly to the most_common_vals, but in this situation those aren't common enough to help much. With such an extensive histogram it is awfully tempting to assume that the histogram members are a representative sample, and take the selectivity as being the fraction of histogram entries that match the pattern. Maybe drop the first and last histogram entries on the grounds they're probably outliers. Thoughts? What would be a reasonable minimum histogram size to enable using this approach instead of the guess-on-the-basis-of-the-pattern code? regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings
