Thread: pgsql: Avoid redundant relation lock grabs during planning, and make

Log Message:
-----------
Avoid redundant relation lock grabs during planning, and make sure
that we acquire a lock on relations added to the query due to inheritance.
Formerly, no such lock was held throughout planning, which meant that
a schema change could occur to invalidate the plan before it's even
been completed.

Modified Files:
--------------
    pgsql/src/backend/optimizer/prep:
        preptlist.c (r1.75 -> r1.76)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/prep/preptlist.c.diff?r1=1.75&r2=1.76)
    pgsql/src/backend/optimizer/util:
        plancat.c (r1.107 -> r1.108)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/util/plancat.c.diff?r1=1.107&r2=1.108)
        relnode.c (r1.65 -> r1.66)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/util/relnode.c.diff?r1=1.65&r2=1.66)