Thread

Re: [HACKERS] Storing rows bigger than one block

Mattias Kregert <matti@algonet.se> — 1998-01-12T17:18:47Z

Darren King wrote:
> > A related question: Is it possible to store tuples over more than one
> > block? Would it be possible to split a big TEXT into multiple blocks?
> Possible, but would cut the access speed to (1 / # blocks), no?

For "big" (multile blocks) rows, maybe. Consecutive blocks should be
buffered by the disk or the os, so I don't think the difference would
be big, or even noticeable.

> There is a var in the tuple header, t_chain, 6.2.1 that has since been
> removed for 6.3.  I think its original purpose was with time-travel,
> _but_, if we go with a ROWID instead of an oid in the future, this could
> be put back in the header and would be the actual address of the next
> block in the chain.
> 
> Oracle has this concept of chained rows.  It is how they implement all
> of their LONG* types and also handle rows of normal types that are
> larger than the block size.

Yes! I can't see why PostgreSQL should not be able to store rows bigger
than one block? I have seen people referring to this limitation every
now and then, but I don't understand why it has to be that way?
Is this something fundamental to PostgreSQL?

/* m */