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Mention selectivity estimation error metrics in README #36

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Mention selectivity estimation error metrics in README #36

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13 changes: 13 additions & 0 deletions doc/README.md
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Expand Up @@ -125,6 +125,19 @@ The extension defines the following functions:
- *execution_count*: number of time this predicate has been executed, ie.
number of rows it processed.
- *nbfiltered*: number of tuples this predicate discarded.
- *min_err_estimate_ratio*: minimum selectivity estimation error ratio
- *max_err_estimate_ratio*: maximum selectivity estimation error ratio
- *mean_err_estimate_ratio*: mean selectivity estimation error ratio
- *stddev_err_estimate_ratio*: standard deviation for selectivity
estimation error ratio
- *min_err_estimate_num*: minimum number of line for selectivity
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that seems a bit obscure. We should find a way to make it clear that those number of lines are the absolute minimum/maximum number of lines the planner were off when estimating a selectivity.

I don't have a better proposal though.

estimation error
- *max_err_estimate_num*: maximum number of line for selectivity
estimation error
- *mean_err_estimate_num*: mean number of line for selectivity
estimation error
- *stddev_err_estimate_num*: standard deviation for number of line for
selectivity estimation error
- *constant_position*: location of the constant in the original query
string, as reported by the parser.
- *queryid*: if pg_stats_statements is installed, the queryid identifying
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