Re: REINDEX ALL and CLUSTER ALL

Tom Lane wrote:
> "scott.marlowe" <scott.marlowe@ihs.com> writes:
> > Sorry, that should have been:
> > Isn't it true that reindex's behavior ON A FAILURE is to simply, quietly 
> > delete the index?  that was reported  ^^^^^^^^^^^^^
> 
> No.
> 
> If you are doing a standalone system index rebuild (with backend -P
> switch) then REINDEX does a "TRUNCATE" of the index relation and
> rebuilds it in place.  If that fails partway through, you'd be left
> with a corrupted index ... which presumably is the same problem you
> started with, so I'm not that concerned about it.
> 
> The TRUNCATE approach is also used for rebuilding indexes on shared
> system relations (pg_database, pg_shadow, pg_group).  This seems
> necessary since REINDEX has no way to update pg_class.relfilenode in
> databases other than the current one.
> 
> In all other cases the rebuild is rollback-able, and a failure should
> leave you exactly where you were before.
> 
> 
> Given these facts I think it would be a bad idea to include the shared
> system relations in any automatic "REINDEX ALL" command.  One could
> make a good argument that any such command should skip *all* system
> tables, actually.

Yes, absolutely. REINDEX is not like vacuum.  It needs to skip all
system tables, I think.  Those indexes are tied into backend structures.


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