pgsql: Fix failure to enforce partitioning contraint for internal parti

Fix failure to enforce partitioning contraint for internal partitions.

When a tuple is inherited into a partitioning root, no partition
constraints need to be enforced; when it is inserted into a leaf, the
parent's partitioning quals needed to be enforced. The previous
coding got both of those cases right. When a tuple is inserted into
an intermediate level of the partitioning hierarchy (i.e. a table
which is both a partition itself and in turn partitioned), it must
enforce the partitioning qual inherited from its parent. That case
got overlooked; repair.

Amit Langote

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/39162b2030fb0a35a6bb28dc636b5a71b8df8d1c

Modified Files
--------------
src/backend/commands/copy.c | 1 -
src/backend/commands/tablecmds.c | 1 -
src/backend/executor/execMain.c | 42 ++++++++++++++++++++++++++++--------
src/include/executor/executor.h | 1 -
src/test/regress/expected/insert.out | 6 ++++++
src/test/regress/sql/insert.sql | 5 +++++
6 files changed, 44 insertions(+), 12 deletions(-)