From: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> |
---|---|
To: | pgsql-hackers(at)lists(dot)postgresql(dot)org |
Cc: | Thomas Munro <munro(at)ip9(dot)org>, Jesper Pedersen <jesper(dot)pedersen(at)redhat(dot)com> |
Subject: | Re: Index Skip Scan |
Date: | 2018-10-09 13:42:24 |
Message-ID: | 153909254478.1479.11809244127214809171.pgcf@coridan.postgresql.org |
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Lists: | pgsql-hackers |
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
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