Thread: pgsql: Fetch XIDs atomically during vac_truncate_clog().

Fetch XIDs atomically during vac_truncate_clog().

Because vac_update_datfrozenxid() updates datfrozenxid and datminmxid
in-place, it's unsafe to assume that successive reads of those values will
give consistent results.  Fetch each one just once to ensure sane behavior
in the minimum calculation.  Noted while reviewing Alexander Korotkov's
patch in the same area.

Discussion: <8564.1464116473@sss.pgh.pa.us>

Branch
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REL9_5_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/bbbe2c97eba37fd8a9e580a596f48935f3d9ded8

Modified Files
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src/backend/commands/vacuum.c | 28 ++++++++++++++++++----------
1 file changed, 18 insertions(+), 10 deletions(-)