Thread: finding fragmented tables

Carin Westblom wrote:
> How can I easily find specific tables and/or databases with a lot of
> space that may be reclaimed w a vacuum full?
>

I picked up this tip on the list a while ago:

SELECT pg_namespace.nspname, pg_class.relname, pg_class.reltuples,
pg_class.relpages, rowwidths.avgwidth, ceil(pg_class.reltuples *
rowwidths.avgwidth::double precision /
current_setting('block_size'::text)::double precision) AS expectedpages,
pg_class.relpages::double precision / ceil(pg_class.reltuples *
rowwidths.avgwidth::double precision /
current_setting('block_size'::text)::double precision) AS bloat,
ceil((pg_class.relpages::double precision *
current_setting('block_size'::text)::double precision - ceil(pg_class.reltuples
* rowwidths.avgwidth::double precision)) / 1024::double precision) AS wastedspace
    FROM ( SELECT pg_statistic.starelid, sum(pg_statistic.stawidth) AS avgwidth
            FROM pg_statistic
           GROUP BY pg_statistic.starelid) rowwidths
    JOIN pg_class ON rowwidths.starelid = pg_class.oid
    JOIN pg_namespace ON pg_namespace.oid = pg_class.relnamespace
   WHERE pg_class.relpages > 1;


then do:

select * from relbloat order by wastedspace desc;

Dan Harris wrote:
> Carin Westblom wrote:
>> How can I easily find specific tables and/or databases with a lot of
>> space that may be reclaimed w a vacuum full?
>>
>
> I picked up this tip on the list a while ago:
>
> SELECT pg_namespace.nspname, pg_class.relname, pg_class.reltuples,
> pg_class.relpages, rowwidths.avgwidth, ceil(pg_class.reltuples *
> rowwidths.avgwidth::double precision /
> current_setting('block_size'::text)::double precision) AS expectedpages,
> pg_class.relpages::double precision / ceil(pg_class.reltuples *
> rowwidths.avgwidth::double precision /
> current_setting('block_size'::text)::double precision) AS bloat,
> ceil((pg_class.relpages::double precision *
> current_setting('block_size'::text)::double precision -
> ceil(pg_class.reltuples * rowwidths.avgwidth::double precision)) /
> 1024::double precision) AS wastedspace
>    FROM ( SELECT pg_statistic.starelid, sum(pg_statistic.stawidth) AS
> avgwidth
>            FROM pg_statistic
>           GROUP BY pg_statistic.starelid) rowwidths
>    JOIN pg_class ON rowwidths.starelid = pg_class.oid
>    JOIN pg_namespace ON pg_namespace.oid = pg_class.relnamespace
>   WHERE pg_class.relpages > 1;
>
>
> then do:
>
> select * from relbloat order by wastedspace desc;

I forgot to add that the select needs to be prepended by:

create view relbloat as ...

sorry about that!

-Dan