Instead of having a configure-time DEFAULT_ATTSTATTARGET, store -1 in

attstattarget to indicate 'use the default'.  The default is now a GUC
variable default_statistics_target, and so may be changed on the fly.  Along
the way we gain the ability to have pg_dump dump the per-column statistics
target when it's not the default.  Patch by Neil Conway, with some kibitzing
from Tom Lane.

src/backend/utils/misc/postgresql.conf.sample

@@ -95,6 +95,7 @@
 #cpu_index_tuple_cost = 0.001
 #cpu_operator_cost = 0.0025
 
+#default_statistics_target = 10	# range 1-1000
 
 #
 #	GEQO Optimizer Parameters