Histogram question. - Mailing list pgsql-sql

From Jian He
Subject Histogram question.
Date
Msg-id CAMV54g17LBTqs069dE5c1EmnGnJXmMtgCNxH5vesjfbJY8_D0g@mail.gmail.com
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Responses Re: Histogram question.  (Steve Midgley <science@misuse.org>)
List 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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