pgsql: Disallow merging ONLY constraints in children tables

Disallow merging ONLY constraints in children tables

When creating a child table, or when attaching an existing table as
child of another, we must not allow inheritable constraints to be
merged with non-inheritable ones, because then grandchildren would not
properly get the constraint. This would violate the grandparent's
expectations.

Bugs noted by Robert Haas.

Author: Nikhil Sontakke

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/3b11247aadf857bbcbfc765191273973d9ca9dd7

Modified Files
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doc/src/sgml/ref/alter_table.sgml | 6 +++++-
src/backend/catalog/heap.c | 19 +++++++++++++++----
src/backend/commands/tablecmds.c | 22 +++++++++++++++++-----
3 files changed, 37 insertions(+), 10 deletions(-)