Re: Support for REINDEX CONCURRENTLY

On Sat, Dec 8, 2012 at 2:19 AM, Andres Freund <andres@2ndquadrant.com>wrote:

> On 2012-12-07 12:01:52 -0500, Tom Lane wrote:
> > Simon Riggs <simon@2ndQuadrant.com> writes:
> > > On 7 December 2012 12:37, Michael Paquier <michael.paquier@gmail.com>
> wrote:
> > >> - There is still a problem with toast indexes. If the concurrent
> reindex of
> > >> a toast index fails for a reason or another, pg_relation will finish
> with
> > >> invalid toast index entries. I am still wondering about how to clean
> up
> > >> that. Any ideas?
> >
> > > Build another toast index, rather than reindexing the existing one,
> > > then just use the new oid.
>
> Thats easier said than done in the first place. toast_save_datum()
> explicitly opens/modifies the one index it needs and updates it.
>
> > Um, I don't think you can swap in a new toast index OID without taking
> > exclusive lock on the parent table at some point.
>
> The whole swapping issue isn't solved satisfyingly as whole yet :(.
>
> If we just swap the index relfilenodes in the pg_index entries itself,
> we wouldn't need to modify the main table's pg_class at all.
>
I think you are mistaking here, relfilenode is a column of pg_class and not
pg_index.
So whatever the method used for swapping: relfilenode switch or relname
switch, you need to modify the pg_class entry of the old and new indexes.
-- 
Michael Paquier
http://michael.otacoo.com