How are null's stored?

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От Jim C. Nasby
Тема How are null's stored?
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Msg-id 20030512190156.GA40542@flake.decibel.org
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Ответы Re: How are null's stored?  (Josh Berkus <josh@agliodbs.com>)
Re: How are null's stored? -- Some numbers  ("Jim C. Nasby" <jim@nasby.net>)
Список pgsql-performance
I have a 40M row table I need to import data into, then use to create a
bunch of more normalized tables. Right now all fields are varchar, but
I'm going to change this so that fields that are less than a certain
size are just char. Question is, how much impact is there from char
being nullable vs. not nullable? src/include/access/htup.h indicates
that nulls are stored in a bitmap, so I'd suspect that I should see a
decent space savings from not having to include length information all
the time... (most of these small fields are always the same size no
matter what...)
--
Jim C. Nasby (aka Decibel!)                    jim@nasby.net
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