RE: [HACKERS] mdnblocks is an amazing time sink in huge relations

>
> Hiroshi Inoue wrote:
> >
> > > > Does this mean the following ?
> > > >
> > > > 1. shared cache holds committed system tuples.
> > > > 2. private cache holds uncommitted system tuples.
> > > > 3. relpages of shared cache are updated immediately by
> > > > phisical change and corresponding buffer pages are
> > > > marked dirty.
> > > > 4. on commit, the contents of uncommitted tuples except
> > > > relpages,reltuples,... are copied to correponding tuples
> > > ^^^^^^^^^
> > > reltuples in shared catalog cache (SCC) will be updated!
> > > If transaction inserted some tuples then SCC->reltuples
> > > will be incremented, etc.
> > >
> >
> > System tuples are only modifiled or (insert and delet)ed like
> > user tuples when reltuples are updated ?
> > If only modified,we couldn't use it in SERIALIZABLE mode.
> ^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^
> ...this...
>
> I'm not sure that we must provide read consistency
> for internal-use columns...

As for relpages,read consistency has no meaning
because they are out of transaction control.
But as for reltuples,isn't it difficult to commit/rollback
correctly without using insert-delete updation ?
Does your WAL system make it possible ?

Regards.

Hiroshi Inoue
Inoue(at)tpf(dot)co(dot)jp