Re: Boolean storage takes up 1 byte?

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От Thom Brown
Тема Re: Boolean storage takes up 1 byte?
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Msg-id bddc86150910010433w3a33d091nb09e4ab7726b53f8@mail.gmail.com
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Ответ на Re: Boolean storage takes up 1 byte?  (Sam Mason <sam@samason.me.uk>)
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2009/10/1 Sam Mason <sam@samason.me.uk>

bool_or and bool_and are aggregates that work over boolean data types.


Ah yes, that makes total sense!  I knew max wouldn't be logical in such as case, but couldn't think of the alternative.  Thanks!
 

I believe it's more to do with the fact that if you add a boolean column
and then subsequently an int column then you're going to struggle to
"pack" them efficiently.  PG always puts columns on the "end" so that you
can add a column in constant time (i.e. no need to rewrite the table
in some common situations).  Once you start doing this then packing is
awkward and a single byte becomes much easier.  Whether the value is
NULL is stored elsewhere in the row.


That's clear now.
 

> And does its storage as a byte affect indexing or query planning?

Not sure which aspects you're referring to here, sorry.

Giving my question more thought, I believe it's pointless.

You've answered my question.  Thanks Sam.

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