| From: | "Jonah H(dot) Harris" <jonah(dot)harris(at)gmail(dot)com> |
|---|---|
| To: | "H(dot) Hall" <hhall1001(at)reedyriver(dot)com> |
| Cc: | pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: "Big O" notation for postgres? |
| Date: | 2008-05-21 14:28:59 |
| Message-ID: | 36e682920805210728p4fa6c12ft592b1045cbae9dfd@mail.gmail.com |
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| Lists: | pgsql-performance |
On Wed, May 21, 2008 at 10:10 AM, H. Hall <hhall1001(at)reedyriver(dot)com> wrote:
> Does anyone know if there is a source that provides "Big O" notation for
> postgres's aggregate functions and operations? For example is count(*) =
> O(1) or O(n)?
I don't know of any document containing the complexity of each
aggregate, but it's sometimes left as a comment in the souce code.
IIRC, COUNT (non-distinct) is currently O(n), where n also includes
evaluation of tuples not represented in the final count (due to
Postgres' MVCC design).
--
Jonah H. Harris, Sr. Software Architect | phone: 732.331.1324
EnterpriseDB Corporation | fax: 732.331.1301
499 Thornall Street, 2nd Floor | jonah(dot)harris(at)enterprisedb(dot)com
Edison, NJ 08837 | http://www.enterprisedb.com/
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