pgsql: Allow ON UPDATE/DELETE SET DEFAULT plans to be cached.

Allow ON UPDATE/DELETE SET DEFAULT plans to be cached.

Once upon a time, somebody was worried that cached RI plans wouldn't get
remade with new default values after ALTER TABLE ... SET DEFAULT, so they
didn't allow caching of plans for ON UPDATE/DELETE SET DEFAULT actions.
That time is long gone, though (and even at the time I doubt this was the
greatest hazard posed by ALTER TABLE...). So allow these triggers to cache
their plans just like the others.

The cache_plan argument to ri_PlanCheck is now vestigial, since there
are no callers that don't pass "true"; but I left it alone in case there
is any future need for it.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/e8c9fd5fdf768323911f7088e8287f63b513c3c6

Modified Files
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src/backend/utils/adt/ri_triggers.c | 24 +++++++++---------
src/test/regress/expected/foreign_key.out | 36 +++++++++++++++++++++++++++++
src/test/regress/sql/foreign_key.sql | 17 +++++++++++++
3 files changed, 65 insertions(+), 12 deletions(-)