Re: Index corruption with CREATE INDEX CONCURRENTLY

On Fri, Feb 17, 2017 at 11:12 AM, Alvaro Herrera <alvherre@2ndquadrant.com>
wrote:

> Keith Fiske wrote:
>
> > Was just curious if anyone was able to come up with any sort of method to
> > test whether an index was corrupted by this bug, other than just waiting
> > for bad query results? We've used concurrent index rebuilding quite
> > extensively over the years to remove bloat from busy systems, but
> > reindexing the entire database "just in case" is unrealistic in many of
> our
> > cases.
>
> As stated, if the CREATE INDEX operates on columns that are previously
> already indexed (which is normally the case when you rebuild because of
> bloat) then there is no chance of index corruption.
>
> Scanning indexes+tables is just as load-intensive as rebuilding the
> indexes anyway.  You don't save any work.  I suppose it can be a problem
> if you have an index big enough that it doesn't fit on your remaining
> free space (but in that case you have a pre-existing problem which you
> should solve anyway).
>
> --
> Álvaro Herrera                https://www.2ndQuadrant.com/
> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
>

It's not the load I'm worried about, it's the locks that are required at
some point during the rebuild. Doing an index rebuild here and there isn't
a big deal, but trying to do it for an entire heavily loaded,
multi-terabyte database is hardly trivial. And I'd say doing a scan is far
less invasive than actually rebuilding the index since little to no writing
is actually being done.

I can understandable if it's simply not possible, but if it is, I think in
any cases of data corruption, having some means to check for it to be sure
you're in the clear would be useful.

Keith