Re: tuptoaster.c must *not* use SnapshotAny

> Tom Lane wrote:
> > 
> > Hiroshi Inoue <Inoue@tpf.co.jp> writes:
> > 
> > > For example is it possible to update a toast
> > > chunk partially using SnapshotToast ?
> > 
> > As things stand (with either SnapshotToast or the old SnapshotAny way)
> > it is never possible to update an individual toast value, either
> > partially or wholly.  All you can do is lay down a new toast value (with
> > a new identifying OID) and then delete the old one.
> > 
> > But I'm not sure that this is wrong, or fixable.  Trying to update part
> > of a toasted value is very much like wanting to update part of an
> > existing row in-place, which we cannot possibly do.
> 
> Bytea seems to be considered as a candidate for BLOB
> though I think the entirely new type is preferable.
> It seems impossible to implement a functionality like
> inv_write using bytea which the current large object
> stuff has.

Agreed.  I think that was the reason we kept TOAST and large objects,
because large objects were designed for random read-write.  If we can
get large objects to auto-delete, probably with pg_depend, we can then
use them seamlessly with BLOB I/O routines.

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