Re: [HACKERS] The number of bytes is stored in index_size of pgstatindex() ?

Peter Geoghegan <pg(at)heroku(dot)com> writes:
> On Thu, Feb 18, 2016 at 9:40 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> I think this is a bug and we ought to fix the code to include the
>> metapage in the reported index_size. Thoughts?

> I tend to agree, but I think you should note that specifically in the
> documentation. I'm in favor of tools like pgstattuple and pageinspect
> going into this kind of detail in their documentation generally.

Yeah ... the numbers already appear not to add up because the root page
is counted in index_size but not any other column, so there's already
something worthy of explanation there. Maybe something like "The reported
index_size will normally correspond to two more pages than are accounted
for by internal_pages + leaf_pages + empty_pages + deleted_pages, because
it also includes the index's metapage and root page".

regards, tom lane