Re: How are null's stored?
От | Ryan |
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Тема | Re: How are null's stored? |
Дата | |
Msg-id | 10995.65.102.128.233.1052765883.squirrel@fordparts.com обсуждение исходный текст |
Ответ на | Re: How are null's stored? (Josh Berkus <josh@agliodbs.com>) |
Ответы |
Re: How are null's stored?
Re: How are null's stored? |
Список | pgsql-performance |
> Jim, > >> 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...) > > This is moot. PostgreSQL stores CHAR(x), VARCHAR, and TEXT in the same > internal format, which includes length information in the page header. > So you save no storage space by converting to CHAR(x) ... you might > even make your tables *larger* because of the space padding. So if the internal format is identical, why does the INFERNAL database ignore indexes when you have a text compared to a varchar? Ryan
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