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From: Tom Lane on 21 Mar 2010 16:07
Gokulakannan Somasundaram <gokul007(a)gmail.com> writes:
> I was looking at the VarBit data structure and found out that instead of
> storing the number of bits in four bytes, we can save the number of bits
> that are valid in the last byte. Since we already store the number of bytes
> in Varlena Header, we can calculate the number of valid bits by doing the
> small math. ( (No. of bytes-1) * 8 + valid bits in the last byte).
> This would save atleast 8 bytes for someone, who is using the varbit data
> type using less than 24 bits.

This might be worth considering in a release cycle where we were going
to break on-disk data compatibility for some other reason. But I can
hardly imagine wanting to do it by itself. Marginal space savings for
the "bit" types just isn't that exciting.

Maybe we should start a special section of TODO for "things we might do
next time we break data compatibility".

regards, tom lane

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From: Gokulakannan Somasundaram on 21 Mar 2010 16:48
> This might be worth considering in a release cycle where we were going
> to break on-disk data compatibility for some other reason. But I can
> hardly imagine wanting to do it by itself. Marginal space savings for
> the "bit" types just isn't that exciting.
>
> Maybe we should start a special section of TODO for "things we might do
> next time we break data compatibility".


Thanks Tom. So when we say breaking data compatibility, we mean the next
release where we will recommend pg_dump/restore right?

Thanks,
Gokul.
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