From: | Vik Fearing <vik(at)postgresfriends(dot)org> |
---|---|
To: | Ankit Kumar Pandey <itsankitkp(at)gmail(dot)com>, David Rowley <dgrowleyml(at)gmail(dot)com> |
Cc: | pghackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
Subject: | Re: Todo: Teach planner to evaluate multiple windows in the optimal order |
Date: | 2023-01-08 16:06:13 |
Message-ID: | 600c351a-ba63-8264-d51a-5d10bf966a52@postgresfriends.org |
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Lists: | pgsql-hackers |
On 1/8/23 11:21, Ankit Kumar Pandey wrote:
>
> Please find attached patch with addressed issues mentioned before.
I am curious about this plan:
+-- ORDER BY's in multiple Window functions can be combined into one
+-- if they are subset of QUERY's ORDER BY
+EXPLAIN (COSTS OFF)
+SELECT empno,
+ depname,
+ min(salary) OVER (PARTITION BY depname ORDER BY empno) depminsalary,
+ sum(salary) OVER (PARTITION BY depname) depsalary,
+ count(*) OVER (ORDER BY enroll_date DESC) c
+FROM empsalary
+ORDER BY depname, empno, enroll_date;
+ QUERY PLAN
+------------------------------------------------------
+ WindowAgg
+ -> WindowAgg
+ -> Sort
+ Sort Key: depname, empno, enroll_date
+ -> WindowAgg
+ -> Sort
+ Sort Key: enroll_date DESC
+ -> Seq Scan on empsalary
+(8 rows)
+
Why aren't min() and sum() calculated on the same WindowAgg run?
--
Vik Fearing
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