Show_database_bloat reliability? [was: Re: REINDEX not working for wastedspace]

AI Rumman <rummandba 'at' gmail.com> writes:

> Using the query http://wiki.postgresql.org/wiki/Show_database_bloat, I got the

Is this stuff to show database bloat reliable? After a VACUUM
FULL of the table reported as the top responsible of bloat,
performing the same request again still gives the same result
(still that table is the top responsible of bloat):

 current_database | schemaname |                tablename                | tbloat | wastedbytes |
iname                         | ibloat | wastedibytes  

------------------+------------+-----------------------------------------+--------+-------------+------------------------------------------------------+--------+--------------
  test            | public     | requests                                |    1.1 |    14565376 | requests_pkey
                              |    0.4 |            0 
  test            | public     | requests                                |    1.1 |    14565376 | idx_whatever
                              |    0.8 |            0 
  test            | public     | requests                                |    1.1 |    14565376 | idx_whatever2
                              |    0.6 |            0 
...

A few investigations show that when tbloat is close to 1.0 then
it seems not reliable, otherwise it seems useful.

pg 8.4.7

--
Guillaume Cottenceau