Re: CLUSTER not lose indexes

Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> Seems like renamerel will have to stay because it is used by ALTER TABLE
> RENAME, so we just need some new code that updates the relfilenode of
> the old pg_class row to point to the new clustered file. Swapping
> relfilenodes between the old and new pg_class rows and deleting the new
> table should do the trick of deleting the non-clustered file and the
> temp pg_class row at the same time.

I think you're still letting your thinking be contorted by the existing
CLUSTER implementation. Do we need a temp pg_class entry at all? Seems
like we just want to UPDATE the pg_class row with the new relfilenode
value; then we can see the update but no one else can (till we commit).
Ditto for the indexes.

What's still a little unclear to me is how to access the old heap and
index files to read the data while simultaneously accessing the new ones
to write it. Much of the existing code likes to have a Relation struct
available, not only a RelFileNode, so it may be necessary to have both
old and new Relations present at the same time. If that's the case we
might be stuck with making a temp pg_class entry just to support a phony
Relation :-(

regards, tom lane