pgsql: Fix tablespace inheritance for partitioned rels

Fix tablespace inheritance for partitioned rels

Commit ca4103025dfe left a few loose ends. The most important one
(broken pg_dump output) is already fixed by virtue of commit
3b23552ad8bb, but some things remained:

* When ALTER TABLE rewrites tables, the indexes must remain in the
tablespace they were originally in. This didn't work because
index recreation during ALTER TABLE runs manufactured SQL (yuck),
which runs afoul of default_tablespace in competition with the parent
relation tablespace. To fix, reset default_tablespace to the empty
string temporarily, and add the TABLESPACE clause as appropriate.

* Setting a partitioned rel's tablespace to the database default is
confusing; if it worked, it would direct the partitions to that
tablespace regardless of default_tablespace. But in reality it does
not work, and making it work is a larger project. Therefore, throw
an error when this condition is detected, to alert the unwary.

Add some docs and tests, too.

Author: Álvaro Herrera
Discussion: https://postgr.es/m/CAKJS1f_1c260nOt_vBJ067AZ3JXptXVRohDVMLEBmudX1YEx-A@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/87259588d0ab0b8e742e30596afa7ae25caadb18

Modified Files
--------------
doc/src/sgml/config.sgml | 3 +-
doc/src/sgml/ref/create_table.sgml | 6 +-
src/backend/bootstrap/bootparse.y | 2 +
src/backend/commands/indexcmds.c | 27 ++-
src/backend/commands/matview.c | 2 +-
src/backend/commands/tablecmds.c | 34 +--
src/backend/commands/tablespace.c | 16 +-
src/backend/nodes/copyfuncs.c | 2 +
src/backend/nodes/equalfuncs.c | 2 +
src/backend/nodes/outfuncs.c | 4 +
src/backend/parser/gram.y | 2 +
src/backend/parser/parse_utilcmd.c | 2 +
src/backend/utils/adt/ruleutils.c | 19 +-
src/include/catalog/catversion.h | 2 +-
src/include/commands/tablespace.h | 2 +-
src/include/nodes/parsenodes.h | 4 +
src/test/regress/input/tablespace.source | 90 ++++++++
src/test/regress/output/tablespace.source | 334 ++++++++++++++++++++++++++++++
18 files changed, 519 insertions(+), 34 deletions(-)