Fix off-by-one error in calculating subtrans/multixact truncation point.
If there were no subtransactions (or multixacts) active, we would calculate
the oldestxid == next xid. That's correct, but if next XID happens to be
on the next pg_subtrans (pg_multixact) page, the page does not exist yet,
and SimpleLruTruncate will produce an "apparent wraparound" warning. The
warning is harmless in this case, but looks very alarming to users.
Backpatch to all supported versions. Patch and analysis by Thomas Munro.
Branch
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REL9_3_STABLE
Details
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http://git.postgresql.org/pg/commitdiff/6ae9a021893b5cd24e1d7e8a1a07854d33af9990
Modified Files
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src/backend/access/transam/multixact.c | 12 ++++++++++--
src/backend/access/transam/subtrans.c | 7 ++++++-
2 files changed, 16 insertions(+), 3 deletions(-)
