Re: [OT] "advanced" database design (long)

That is a very awesome system. I am constantly impressed at the
awesomeness of Postgresql.

Alex

On Feb 4, 2008 1:06 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Jorge Godoy <jgodoy(at)gmail(dot)com> writes:
> > Em Monday 04 February 2008 07:03:47 Dawid Kuroczko escreveu:
> >> Well, but PostgreSQL's NULLs occupy almost no space, or rather a bit of
> >> space, that is one bit exactly. ;-) I am pretty much sure that
> >> storage-wise looking NULLs
> >> are more efficient.
>
> > I'd say 1 byte every 8 NULLs instead of 1 bit. If you only have 1 NULL, it
> > will cost you 1 byte (not 1 bit). If you have 9, it will cost you 2 bytes
> > (not 9 bits).
>
> This is not quite right --- the amount of space used doesn't change if
> you have more or fewer nulls in a row. A null bitmap is present in a
> row if there are any nulls at all in the row, and its size will be equal
> to the defined number of columns in the table. As you say, there's
> padding overhead too ...
>
> regards, tom lane
>
>
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