[BUGS] BUG #14676: neqsel is NULL dumb
От | marko@joh.to |
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Тема | [BUGS] BUG #14676: neqsel is NULL dumb |
Дата | |
Msg-id | 20170529153847.4275.95416@wrigleys.postgresql.org обсуждение исходный текст |
Ответы |
Re: [BUGS] BUG #14676: neqsel is NULL dumb
Re: [BUGS] BUG #14676: neqsel is NULL dumb |
Список | pgsql-bugs |
The following bug has been logged on the website: Bug reference: 14676 Logged by: Marko Tiikkaja Email address: marko@joh.to PostgreSQL version: 9.6.3 Operating system: Linux Description: I'm having an issue with a case where a column is mostly NULLs and I'm doing an inequality query on the column: =# create table foo(nullable int); CREATE TABLE =# insert into foo select case when i = 1 then i else null end from generate_series(1, 1000) gs(i); INSERT 0 1000 =# analyze foo; ANALYZE =# explain select * from foo where nullable <> 1; QUERY PLAN ------------------------------------------------------Seq Scan on foo (cost=0.00..16.50 rows=999 width=4) Filter: (nullable<> 1) (2 rows) This seems to be because neqsel() doesn't take at all into account that both operators will exclude NULL rows, and does a simple 1.0 - eqsel(). This also means that a partial index such as: create index on foo(othercolumn) where nullable <> 1 will never be used. -- Sent via pgsql-bugs mailing list (pgsql-bugs@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-bugs
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