On 2019-Apr-11, Michael Paquier wrote:
> > I was going to just remove the caveat, but then I discovered that
> > REINDEX CONCURRENTLY doesn't work on INVALID indexes (why?).
>
> This is a wanted choice. The index built in parallel of the existing
> one during a concurrent reindex is marked invalid during most of the
> operation. Hence, if the reindex is interrupted or fails, you finish
> with potentially twice the number of original indexes, half being
> invalid and the other half being the ones in use. If the user decides
> to rinse and repeat the concurrent reindex, and if we were to also
> select invalid indexes for the operation, then you would finish by
> potentially doing twice the amount of work when working on a relation,
> half of it for nothing.
Hmm, I suppose that makes sense for REINDEX TABLE or anything that
reindexes more than one index, but if you do REINDEX INDEX surely it
is reasonable to allow the case?
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
