[postgis-devel] Re: [postgis-users] create tables smarter

[Kevin Neufeld]

Stephen Frost wrote:
> My suggestion, assuming 4 bytes, would be:
>
> Negative: 1 bit
> COORD_DIMENSION: 2 bits
> TYPE: 6 bits
> SRID: 23 bits
>
> That allows for 4 coordinate dimensions (only 3 currently exist), 64
> types (only 15? or so now), and over 8M SRIDs.  If we think that SRIDs
> won't go over 1M, we could give it only 20 bits and keep the other 3
> bits for 'future expansion'.
>
>   
I think there are actually 4 dimensions now. X,Y,Z,and M.  There once 
was talk of working towards having N dimensions.  Do we still want to go 
there?  In which case, I would recommend that, for now, we use 4-5 bits 
for COORD_DIMENSION and 20-21 for SRID.

-- Kevin