Dump/Restore performance improvement

Greetings,

I have observed that in a dump/restore scenario the longest time is
spent on index creation for larger tables, I have a suggestion of how
the performance could be improved thus reducing the time to recover
from a crash. Not sure if this is possible but would definitely be a
nice addition to the TODO list.

1) Add a new config paramter e.g work_maintanence_max_mem this will
the max memory postgresql *can* claim if need be.

2) During the dump phase of the DB postgresql estimates the
"work_maintenance_mem" that would be required to create the index in
memory(if possible) and add's a
SET work_maintenance_mem="the value calculated" (IF this value is less
than work_maintanence_max_mem. )

3) During the restore phase the appropriate memory is allocated in RAM
and the index creation takes less time since PG does not have to sort
on disk.

--
Adi Alurkar (DBA sf.NET) <adi(at)vasoftware(dot)com>
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