Hi
I tested last patch and I have some notes:
1.
postgres=# explain select distinct a10000 from foo;
+-------------------------------------------------------------------------------------------+
| QUERY PLAN |
+-------------------------------------------------------------------------------------------+
| Unique (cost=0.43..4367.56 rows=9983 width=4) |
| -> Index Skip Scan using foo_a10000_idx on foo (cost=0.43..4342.60 rows=9983 width=4) |
+-------------------------------------------------------------------------------------------+
(2 rows)
In this case Unique node is useless and can be removed
2. Can be nice COUNT(DISTINCT support) similarly like MIN, MAX suppport
3. Once time patched postgres crashed, but I am not able to reproduce it.
Looks like very interesting patch, and important for some BI platforms
