Histogram question.
| От | Jian He |
|---|---|
| Тема | Histogram question. |
| Дата | |
| Msg-id | CAMV54g17LBTqs069dE5c1EmnGnJXmMtgCNxH5vesjfbJY8_D0g@mail.gmail.com обсуждение исходный текст |
| Ответы |
Re: Histogram question.
|
| Список | pgsql-sql |
SELECT sum(s.most_common_freqs[ array_position((s.most_common_vals::text::text[]),v) ]) FROM pg_stats s, unnest(s.most_common_vals::text::text[]) v WHERE s.tablename = 'boarding_passes' AND s.attname = 'seat_no';
return 0.6762.
SELECT sum(s.most_common_freqs[ array_position((s.most_common_vals::text::text[]),v) ]) FROM pg_stats s, unnest(s.most_common_vals::text::text[]) v WHERE s.tablename = 'boarding_passes' AND s.attname = 'seat_no' AND v > '30C';
return 0.2127
SELECT round( reltuples * ( 0.2127 -- from most common values + (1 - 0.6762 - 0) * (49 / 100.0) -- from histogram )) FROM pg_class WHERE relname = 'boarding_passes';
the above mentioned query, the part I don't understand is 49/100.
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