On 21/09/11 06:09, Josh Berkus wrote:
Venkat,
I see lot of free spaces or free pages in Tables and Indexes. But, I need to
give an exact calculation on how much space will be reclaimed after VACUUM
FULL and RE-INDEXING.
At present, there is no way to calculate this precisely. You can only
estimate, and estimates have significant error factors. The query which
Marcin linked for you, for example, can be as much as 500% off (although
usually only 50% off).
If you have autovacuum on (which should be typical thee days), then
using the freespacemap contrib module should give very accurate results:
SELECT oid::regclass,
pg_relation_size(oid)/(1024*1024) AS mb,
sum(free)/(1024*1024) AS free_mb
FROM
(SELECT oid, (pg_freespace(oid)).avail AS free
FROM pg_class) AS a
GROUP BY a.oid ORDER BY free_mb DESC;
regards
Mark
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