pgsql: Reduce WAL activity for page splits: > Currently, an index split

Log Message:
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Reduce WAL activity for page splits:

> Currently, an index split writes all the data on the split page to
> WAL. That's a lot of WAL traffic. The tuples that are copied to the
> right page need to be WAL logged, but the tuples that stay on the
> original page don't.

Heikki Linnakangas

Modified Files:
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    pgsql/src/backend/access/nbtree:
        nbtinsert.c (r1.149 -> r1.150)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/nbtree/nbtinsert.c.diff?r1=1.149&r2=1.150)
        nbtxlog.c (r1.41 -> r1.42)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/nbtree/nbtxlog.c.diff?r1=1.41&r2=1.42)
    pgsql/src/include/access:
        nbtree.h (r1.110 -> r1.111)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/access/nbtree.h.diff?r1=1.110&r2=1.111)