Re: [HACKERS] Tuple size

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От Steve A Fink
Тема Re: [HACKERS] Tuple size
Дата
Msg-id bebd562b647d10a3d10b812abd432958
обсуждение исходный текст
Ответ на [HACKERS] Tuple size  (Alexander Demenshin <aldem@techie.com>)
Список pgsql-hackers
I can take a guess...

>   Well, I understand why, but type 'char' is *fixed* length type,
>   so even if I don't use some attributes, it *must* be inserted
>   with all spaces... At least, I expected this... In this case
>   I must get "tuple is too big" even if I will insert "empty"
>   record. It is not so - why?

Your first insertion had nulls for the other two positions. Tuples are
stored with a bit vector specifying which columns are null. Null columns
are not stored. So the example fit into one page, no problem. If you had
inserted empty strings in the other two char()s, then you would have run
out of space.

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