pgsql: Improve ALTER TABLE documentation

Improve ALTER TABLE documentation

The ALTER TABLE documentation wasn't terribly clear when it came to
which commands could be combined together and what it meant when they
were.

In particular, SET TABLESPACE *can* be combined with other commands,
when it's operating against a single table, but not when multiple tables
are being moved with ALL IN TABLESPACE. Further, the actions are
applied together but not really in 'parallel', at least today.

Pointed out by: Amit Langote

Improved wording from Tom.

Back-patch to 9.4, where the ALL IN TABLESPACE option was added.

Discussion: https://www.postgresql.org/message-id/14c535b4-13ef-0590-1b98-76af355a0763%40lab.ntt.co.jp

Branch
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REL9_4_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/b5fe1d4cd93d281eef7ab6718716d169609b000a

Modified Files
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doc/src/sgml/ref/alter_table.sgml | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)