..On 25 April 2017 at 13:31, Bruce Momjian <bruce@momjian.us> wrote:
> The only unusual thing is that this release has ~180 items while most
> recent release have had ~220. The pattern I see that there are more
> large features in this release than previous ones.
Thanks for drafting this up.
I understand that it may have been filtered out, but I'd say that
7e534adcdc70 is worth a mention.
Users creating BRIN indexes previously would have had to know
beforehand that the table would be sufficiently correlated on the
indexed columns for the index to be worthwhile, whereas now there's a
lesser need for the user to know this beforehand.
Also:
<para>
New commands are <command><link linkend="SQL-CREATESTATISTICS">CREATE</></>,
<command><link linkend="SQL-ALTERSTATISTICS">ALTER</></>, and
<command><link linkend="SQL-DROPSTATISTICS">DROP STATISTICS</></>.
This is helpful in
estimating query memory usage and ... HOW IS RATIO USED?
</para>
HOW IS RATIO USED? .... There are two types of new stats;
ndistinct, which can improve row estimations in the query planner for
estimating the number of distinct value groups over multiple columns.
functionaldeps, which provides the planner with a better understanding
of functional depdenences between columns on which the statistics are
defined. The planner takes the functional dependency degree into
account when multiplying selectivity estimations for multiple columns.
Unsure how best to trim that down to something short enough for the
release notes.
-- David Rowley http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services
