pgsql: Update visibility map in the second phase of vacuum.

Update visibility map in the second phase of vacuum.

There's a high chance that a page becomes all-visible when the second phase
of vacuum removes all the dead tuples on it, so it makes sense to check for
that. Otherwise the visibility map won't get updated until the next vacuum.

Pavan Deolasee, reviewed by Jeff Janes.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/fdf9e21196a6f58c6021c967dc5776a16190f295

Modified Files
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src/backend/commands/vacuumlazy.c |  133 +++++++++++++++++++++++++++++++++++-
1 files changed, 129 insertions(+), 4 deletions(-)