Обсуждение: pgsql: Clamp last_anl_tuples to n_live_tuples, in case we vacuum a table

Log Message:
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Clamp last_anl_tuples to n_live_tuples, in case we vacuum a table without
analyzing, so that future analyze threshold calculations don't get confused.
Also, make sure we correctly track the decrease of live tuples cause by
deletes.

Per report from Dylan Hansen, patches by Tom Lane and me.

Modified Files:
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    pgsql/src/backend/postmaster:
        pgstat.c (r1.130 -> r1.131)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/pgstat.c.diff?r1=1.130&r2=1.131)