Tom Lane wrote:
ITAGAKI Takahiro <[EMAIL PROTECTED]> writes:
Our documentation says
| analyze threshold = analyze base threshold
| + analyze scale factor * number of tuples
| is compared to the total number of tuples inserted, updated, or deleted
| since the last ANALYZE.
but deleted tuples are not considered in the total number, because the delta
of {n_live_tuples + n_dead_tuples} is not changed by DELETE. We add the number
of DELETE into n_live_tuples and subtract it from n_dead_tuples.
Yeah, I was concerned about that when I was making the patch, but didn't
see any simple fix. A large number of DELETEs (without any inserts or
updates) would trigger a VACUUM but not an ANALYZE, which in the worst
case would be bad because the stats could have shifted.
We could fix this at the cost of carrying another per-table counter in
the stats info, but I'm not sure it's worth it.
I believe that whenever autovacuum performs a VACUUM it actually
performs a VACUUM ANALYZE at leas the old contrib version did and I
think Alvaro copied that.
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