Re: reading vacuum verbosity

On Friday May 21 2004 1:04, Tom Lane wrote:
> "Ed L." <pgsql(at)bluepolka(dot)net> writes:
> > Below are 3 snippets from 3 successive vacuums on a table
> > with ~284K rows which receives many many UPDATEs and a few
> > INSERTs (there were also a few runs of ANALYZE in between
> > these VACUUMs):
> >
> > INFO: Pages 22652: Changed 4, Empty 0; Tup 284139: Vac 927, Keep 0,
> > UnUsed 936. INFO: Pages 22652: Changed 7, Empty 0; Tup 284151: Vac
> > 423, Keep 0, UnUsed 1559. INFO: Pages 22652: Changed 4, Empty 0; Tup
> > 284155: Vac 221, Keep 0, UnUsed 1823.
>
> That looks okay to me considering that the physical table size (Pages)
> isn't growing.
>
> > 1) Do the increasing values for "UnUsed" indicate leakage?
>
> I'm not sure. It seems a bit odd ... could you track this over a longer
> interval? An unused tuple slot will only take 4 bytes so it might take
> awhile to see any real consequence.

Here's a longer interval, or at least a longer sequence:

INFO: Pages 22652: Changed 4, Empty 0; Tup 284139: Vac 927, Keep 0, UnUsed 936.
INFO: Pages 22652: Changed 7, Empty 0; Tup 284151: Vac 423, Keep 0, UnUsed 1559.
INFO: Pages 22652: Changed 4, Empty 0; Tup 284155: Vac 221, Keep 0, UnUsed 1823.
INFO: Pages 22652: Changed 2, Empty 0; Tup 284164: Vac 655, Keep 0, UnUsed 1592.
INFO: Pages 22652: Changed 1, Empty 0; Tup 284169: Vac 87, Keep 0, UnUsed 2184.
INFO: Pages 22652: Changed 1, Empty 0; Tup 284170: Vac 121, Keep 0, UnUsed 2179.
INFO: Pages 22652: Changed 0, Empty 0; Tup 284170: Vac 0, Keep 0, UnUsed 2300.
INFO: Pages 22652: Changed 0, Empty 0; Tup 284170: Vac 0, Keep 0, UnUsed 2300.
INFO: Pages 22652: Changed 1, Empty 0; Tup 284171: Vac 94, Keep 0, UnUsed 2230.
INFO: Pages 22652: Changed 0, Empty 0; Tup 284171: Vac 0, Keep 0, UnUsed 2324.
INFO: Pages 22652: Changed 0, Empty 0; Tup 284171: Vac 0, Keep 0, UnUsed 2324.
INFO: Pages 22652: Changed 1, Empty 0; Tup 284172: Vac 97, Keep 0, UnUsed 2232.
INFO: Pages 22652: Changed 1, Empty 0; Tup 284173: Vac 106, Keep 0, UnUsed 2242.
INFO: Pages 22652: Changed 0, Empty 0; Tup 284203: Vac 36, Keep 0, UnUsed 2311.

I see the UnUsed number stabilizing a bit. (I realize a few of these
vacuums were unnecessary).