Add postgres WINDOW keyword

Postgres allows statements of the form:
```sql
SELECT col_1, col_2, SUM(col_3) OVER w
FROM x
WINDOW w AS (PARTITION BY col_1 ORDER BY col_2)
```
where the window is defined once at the end of the query (see
https://www.postgresql.org/docs/9.5/sql-select.html).

This change adds WINDOW as a postgres keyword, preventing queries like
the above being misparsed, with table name and WINDOW being grouped into
an single identifier <Identifier 'x WINDOW'>.

1 files changed, 1 insertions, 0 deletions

diff --git a/sqlparse/keywords.py b/sqlparse/keywords.py
index 68ced92..8c872fd 100644
--- a/sqlparse/keywords.py
+++ b/sqlparse/keywords.py
@@ -833,6 +833,7 @@ KEYWORDS_ORACLE = {
 
 # PostgreSQL Syntax
 KEYWORDS_PLPGSQL = {
+    'WINDOW': tokens.Keyword,
     'PARTITION': tokens.Keyword,
     'OVER': tokens.Keyword,
     'PERFORM': tokens.Keyword,