Jean-Arthur Silve <jeanarthur@eurovox.fr> writes:
> NOTICE: Pages 7430: Changed 0, Empty 0; Tup 154392: Vac 6271, Keep 0,
> UnUsed 451218.
> Total CPU 0.05s/0.34u sec elapsed 1.80 sec.
> what is the difference wetween Vac and and unUsed ?
IIRC, "Vac" is the number of tuples freed in this VACUUM pass.
"UnUsed" is the total number of free tuple slots (linepointers) in the
table. I'm not sure if that includes the just-freed ones or not.
> Is unUsed spaces unUsed but not deleted ?
Freed slot pointers are available for re-use later. But the fact that
there are many more free pointers than used pointers (450k vs 155k in
your example) suggests to me that a VACUUM FULL might be appropriate.
If you find that VACUUM FULL reduces the file size (number of pages)
significantly, then you should plan on more frequent regular VACUUMs
and/or increasing the postmaster's FSM parameters to prevent dead
space from accumulating again.
regards, tom lane