| From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
|---|---|
| To: | Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp> |
| Cc: | "Colin 't Hart" <colin(at)sharpheart(dot)org>, PostgreSQL mailing lists <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Order of columns in query is important?! |
| Date: | 2015-05-26 10:32:08 |
| Message-ID: | CANP8+jL0KjFE3+zC=YBA+oPrLn7QPYyUnGAwWmm9c2YYb1XZmQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 25 May 2015 at 11:48, Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp> wrote:
> On 2015-05-25 PM 06:26, Colin 't Hart wrote:
>
> That means the specified order of columns in a query does matter which
> would
> have to match the defined order in order to avoid extra processing (that is
> only when specified columns *exactly* matches the tuple descriptor).
>
...and it matters a lot in those cases because we are sorting all of the
data scanned, not just 25 rows.
--
Simon Riggs http://www.2ndQuadrant.com/
<http://www.2ndquadrant.com/>
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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