pgsql: Allow ALTER TABLE ONLY on partitioned tables

Allow ALTER TABLE ONLY on partitioned tables

There is no need to forbid ALTER TABLE ONLY on partitioned tables,
when no partitions exist yet. This can be handy for users who are
building up their partitioned table independently and will create actual
partitions later.

In addition, this is how pg_dump likes to operate in certain instances.

Author: Amit Langote, with some error message word-smithing by me

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/9139aa19423b736470f669e566f8ef6a7f19b801

Modified Files
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doc/src/sgml/ddl.sgml | 18 ++++++---
src/backend/commands/tablecmds.c | 66 +++++++++++++++++++------------
src/test/regress/expected/alter_table.out | 36 +++++++++++------
src/test/regress/expected/truncate.out | 8 ++++
src/test/regress/sql/alter_table.sql | 24 ++++++++---
src/test/regress/sql/truncate.sql | 4 ++
6 files changed, 108 insertions(+), 48 deletions(-)