Re: extensible external toast tuple support & snappy prototype

* Andres Freund (andres(at)2ndquadrant(dot)com) wrote:
> Currently on a little endian system the pglz header contains the length
> in the first four bytes as:
> [dddddddd][dddddddd][dddddddd][xxdddddd]
> Where dd are valid length bits for pglz and xx are the two bits which
> are always zero since we only ever store up to 1GB. We can redefine 'xx'
> to mean whatever we want but we cannot change it's place.

I'm not thrilled with the idea of using those 2 bits from the length
integer. I understand the point of it and that we'd be able to have
binary compatibility from it but is it necessary to track at the
per-tuple level..? What about possibly supporting >1GB objects at some
point (yes, I know there's a lot of other issues there, but still).
We've also got complexity around the size of the length integer already.

Anyway, just not 100% sure that we really want to use these bits for
this.

Thanks,

Stephen