Re: CLUSTER not lose indexes

Alvaro Herrera wrote:
> Bruce Momjian dijo:
>
> > Alvaro Herrera wrote:
> > > Hackers:
> > >
> > > I've modified commands/cluster.c so that it recreates the indexes on the
> > > table after clustering the table.  I attach the patch.
>
> > I think Tom was suggesting that you may want to continue work on CLUSTER
> > and make use of relfilenode.  After the cluster, you can just update
> > pg_class.relfilenode with the new file name (random oid generated at
> > build time) and as soon as you commit, all backends will start using the
> > new file and you can delete the old one.
>
> I'm looking at pg_class, and relfilenode is equal to oid in all cases
> AFAICS.  If I create a new, "random" relfilenode, the equality will not
> hold.  Is that OK?  Also, is the new relfilenode somehow guaranteed to

Yes, they are all the same only because we haven't gotten CLUSTER fixed
yet.  ;-)  We knew we needed to make cases where they are not the same
specifically for cases like CLUSTER.

> not be assigned to another relation (pg_class tuple, I think)?

It will be fine.  The relfilenode will be the one assigned to the new
heap table and will not be used by others.

>
>
> > In this code, we delete the old relation, then rename the new one.  It
> > would be good to have this all happen in one update of
> > pg_class.relfilenode;  that way it is an atomic operation.
>
> OK, I'll see if I can do that.
>
> > Let us know if you want to pursue that and we can give you additional
> > assistance.  I would like to see CLUSTER really polished up.  More
> > people are using it now and it really needs someone to focus on it.
>
> I thought CLUSTER was meant to be replaced by automatically clustering
> indexes.  Isn't that so?  Is anyone working on that?

We have no idea how to automatically cluster based on an index.  Not
even sure how the commercial guys do it.

> > Glad to see you working on CLUSTER.  Welcome aboard.
>
> Thank you.  I'm really happy to be able to work in Postgres.

Great.

--
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026