Re: pg_stat_all_tables vs NULLs

Magnus Hagander wrote:
> Tom Lane wrote:
> > Magnus Hagander <magnus@hagander.net> writes:
> >> I've noticed that pg_stat_all_tables returns NULL for idx_scan and
> >> idx_tup_fetch if there are no indexes present on a table.
> > 
> >> Is this actually intended, or is that something that should be fixed?
> > 
> > Hmm.  I suspect it's an implementation artifact rather than something
> > that was consciously chosen, but on reflection it doesn't seem like a
> > bad thing.  If we just COALESCE'd it to zero (which I assume is what
> > you have in mind) then there would be no distinction in the view
> > between "you have no indexes" and "there are indexes but they aren't
> > being used".
> 
> But does it make sense to look for that information in pg_stat_*_tables,
> really? If you want to know if an index exists for a table, you'd
> normally go look in the system tables, not the statistics views, I think.
> 
> 
> > I'd vote to leave it alone, I think.
> 
> I can go for that as well though. I'd say "Let's document it instead
> then", but it seems the stats views documentation is very short on what
> actually goes in the fields. But I guess we could just add a "(NULL if
> no indexes are present)" to that?
> 
> In the long term it might be worthwhile to rewrite that section of the
> docs to focus more on the stats views (giving each it's own section with
> more information bout it than just a list of fields) and less on the
> underlying implementation functions. But that's a different day ;-)

I don't see any clean place to put this information in our
documentation, and since this is the first report of confusion, I don't
think we can easily document this.

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com
 + If your life is a hard drive, Christ can be your backup. +