pgsql: Split up wal-logging items: < * Allow control over which tables

Log Message:
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Split up wal-logging items:

< * Allow control over which tables are WAL-logged [walcontrol]

* Allow WAL logging to be turned off for a table, but the table
might be dropped or truncated during crash recovery [walcontrol]

< commit. To do this, only a single writer can modify the table, and
< writes must happen only on new pages. Readers can continue accessing
< the table. This would affect COPY, and perhaps INSERT/UPDATE too.
< Another option is to avoid transaction logging entirely and truncate
< or drop the table on crash recovery. These should be implemented
< using ALTER TABLE, e.g. ALTER TABLE PERSISTENCE [ DROP | TRUNCATE |
< STABLE | DEFAULT ]. Tables using non-default logging should not use
< referential integrity with default-logging tables, and tables using
< stable logging probably can not have indexes. One complexity is
< the handling of indexes on TOAST tables.

commit. This should be implemented using ALTER TABLE, e.g. ALTER
TABLE PERSISTENCE [ DROP | TRUNCATE | DEFAULT ]. Tables using
non-default logging should not use referential integrity with
default-logging tables. A table without dirty buffers during a
crash could perhaps avoid the drop/truncate.

* Allow WAL logging to be turned off for a table, but the table would
avoid being truncated/dropped [walcontrol]

To do this, only a single writer can modify the table, and writes
must happen only on new pages so the new pages can be removed during
crash recovery. Readers can continue accessing the table. Such
tables probably cannot have indexes. One complexity is the handling
of indexes on TOAST tables.

Modified Files:
--------------
pgsql/doc:
TODO (r1.1757 -> r1.1758)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/TODO.diff?r1=1.1757&amp;r2=1.1758)
pgsql/doc/src/FAQ:
TODO.html (r1.262 -> r1.263)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/FAQ/TODO.html.diff?r1=1.262&amp;r2=1.263)