[PATCH] Extending pg_class info + more flexible TOAST chunk size

Bacause MAX_TOAST_CHUNK_SIZE is related on page layout version I need have toast
chunk size more flexible.

Attached patch add three new columns into pg_class

relblocksize - which is always BLCKSZ. I put it there for fullness, but i could
be use in future development to specify different BLCKSZ per relation.

relsegsize - currently it is always RELSEG_FILE. I performed basic adjustment in
smgr.c and md.c. Now only smgropen contains reference to RELSEG_FILE. The
problem how to do it fully dynamic is how to pass information rel_rd->relsegsize
down into smgropen. One idea is to extend relfilenode, but I'm not sure about it.

relmaxitemsize - it is set to TOAST_MAX_CHUNK_SIZE. Other relation has this
value set to zero for now. toast functions are fully aware about this setting
and use it. This column will be convert to int2vector during pg_upgrade
development (I need to track information for each page version).

Additional work could be add CRATE TABLE ... WITH chunksize=xxxx

Patch requires increase control file version and catalog version.

    thanks for your comments
            Zdenek

--
Zdenek Kotala              Sun Microsystems
Prague, Czech Republic     http://sun.com/postgresql