Re: Proposal for Byte savings in VarBit structure

Gokulakannan Somasundaram <gokul007@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