Re: Bloated indexes from pg_restore? (Was: Index fillfactor changed in pg9?)

Glyn Astill <glynastill(at)yahoo(dot)co(dot)uk> writes:
> --- On Mon, 4/4/11, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>> So it appears now that if I restore the database using
>>> pg_restore, I end up with bloated indexes, which are fixed
>>> with a vacuum full.
>>>
>>> The dump is a data only dump with the -Fc flag,

>> Data only dump? Then what is the state of the
>> database you're restoring it into?

> It's a newly created database from a schema only dump.

So the difference is that you have initially-empty indexes that are
filled incrementally, whereas an ordinary dump-and-restore would be
creating fresh indexes. Incremental filling of a btree is usually said
to result in about 66% fillfactor on average, 50% worst-case; whereas by
default I think we build fresh indexes at 90% fillfactor. You didn't
say how much "bloat" you were seeing, but if it's less than 2X I think
this is just expected. Unless the data is pretty static, it's useless
to hope that the fill factor will stay as high as 90% anyway.

regards, tom lane