Add ideas for concurrent pg_dump and pg_restore:

Add ideas for concurrent pg_dump and pg_restore:

< * pg_dump
> * pg_dump / pg_restore
> 	o Allow pg_dump to utilize multiple CPUs and I/O channels by dumping
> 	  multiple objects simultaneously
>
> 	  The difficulty with this is getting multiple dump processes to
> 	  produce a single dump output file.
> 	  http://archives.postgresql.org/pgsql-hackers/2008-02/msg00205.php
>
> 	o Allow pg_restore to utilize multiple CPUs and I/O channels by
>           restoring multiple objects simultaneously
>
> 	  This might require a pg_restore flag to indicate how many
> 	  simultaneous operations should be performed.  Only pg_dump's
> 	  -Fc format has the necessary dependency information.
>
> 	o To better utilize resources, restore data, primary keys, and
>  	  indexes for a single table before restoring the next table
>
> 	  Hopefully this will allow the CPU-I/O load to be more uniform
> 	  for simultaneous restores.  The idea is to start data restores
> 	  for several objects, and once the first object is done, to move
> 	  on to its primary keys and indexes.  Over time, simultaneous
> 	  data loads and index builds will be running.
>
> 	o To better utilize resources, allow pg_restore to check foreign
> 	  keys simultaneously, where possible
> 	o Allow pg_restore to create all indexes of a table
> 	  concurrently, via a single heap scan
>
> 	  This requires a pg_dump -Fc file because that format contains
>           the required dependency information.
> 	  http://archives.postgresql.org/pgsql-general/2007-05/msg01274.php
>
> 	o Allow pg_restore to load different parts of the COPY data
> 	  simultaneously
<   single heap scan, and have a restore of a pg_dump somehow use it
>   single heap scan, and have pg_restore use it
<   http://archives.postgresql.org/pgsql-general/2007-05/msg01274.php