pgsql: docs: Improve window function docs

docs: Improve window function docs

Specifically, the behavior of general-purpose and statistical aggregates
as window functions was not clearly documented, and terms were
inconsistently used. Also add docs about the difference between
cume_dist and percent_rank, rather than just the formulas.

Discussion: 20170406214918.GA5757@momjian.us

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/1c1a4726eba5bb8c0772db8a8efe0315d71887fb

Modified Files
--------------
doc/src/sgml/advanced.sgml | 31 +++++++++++++++----------------
doc/src/sgml/func.sgml | 44 ++++++++++++++++++++++++++++----------------
doc/src/sgml/syntax.sgml | 27 ++++++++++++++-------------
3 files changed, 57 insertions(+), 45 deletions(-)

--
Sent via pgsql-committers mailing list (pgsql-committers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-committers