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

Zdenek Kotala <Zdenek.Kotala@Sun.COM> writes:
> 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).

There is not one of these things that we have any intention of being
allowed to vary on a per-relation basis.  Why don't you read them out of
pg_control?
        regards, tom lane