Mention statistics objects in maintenance.sgml
The docs mentioned expression indexes as a way to improve selectivity
estimates for functions, but we have a second option to improve that by
creating extended statistics. So mention that too.
Reported-by: Justin Pryzby
Discussion:
<para>
Also, by default there is limited information available about
- the selectivity of functions. However, if you create an expression
+ the selectivity of functions. However, if you create a statistics
+ object or an expression
index that uses a function call, useful statistics will be
gathered about the function, which can greatly improve query
plans that use the expression index.
