Dead or half-dead index leaf pages were incorrectly reported as live, as a
consequence of a code rearrangement I made (during a moment of severe brain
fade, evidently) in commit d287818eb5.
The index metapage was not counted in index_size, causing that result to
not agree with the actual index size on-disk.
Index root pages were not counted in internal_pages, which is inconsistent
compared to the case of a root that's also a leaf (one-page index), where
the root would be counted in leaf_pages. Aside from that inconsistency,
this could lead to additional transient discrepancies between the reported
page counts and index_size, since it's possible for pgstatindex's scan to
see zero or multiple pages marked as BTP_ROOT, if the root moves due to
a split during the scan. With these fixes, index_size will always be
exactly one page more than the sum of the displayed page counts.
Also, the index_size result was incorrectly documented as being measured in
pages; it's always been measured in bytes. (While fixing that, I couldn't
resist doing some small additional wordsmithing on the pgstattuple docs.)
Including the metapage causes the reported index_size to not be zero for
an empty index. To preserve the desired property that the pgstattuple
regression test results are platform-independent (ie, BLCKSZ configuration
independent), scale the index_size result in the regression tests.
The documentation issue was reported by Otsuka Kenji, and the inconsistent
root page counting by Peter Geoghegan; the other problems noted by me.
Back-patch to all supported branches, because this has been broken for
a long time.
This allows us to specify the target relation with several expressions,
'relname', 'schemaname.relname' and OID in all pgstattuple functions.
pgstatindex() and pg_relpages() could not accept OID as the argument
so far.
Per discussion on -hackers, we decided to keep two types of interfaces,
with regclass-type and TEXT-type argument, for each pgstattuple
function because of the backward-compatibility issue. The functions
which have TEXT-type argument will be deprecated in the future release.
Patch by Satoshi Nagayasu, reviewed by Rushabh Lathia and Fujii Masao.
Tom Lane
Fujii Masao
Heikki Linnakangas