| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Pei He <hepeimail(at)gmail(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Szymon Guz <mabewlun(at)gmail(dot)com>, Kevin(dot)Grittner(at)wicourts(dot)gov, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Get the offset of a tuple inside a table |
| Date: | 2010-09-22 10:31:13 |
| Message-ID: | AANLkTi=5YO49BCjay+E07cKFH=23_J3KA-gnO1Y7Q_p1@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Tue, Sep 21, 2010 at 10:58 PM, Pei He <hepeimail(at)gmail(dot)com> wrote:
> Hi Tom,
> The bitmapset works for me.
>
> I want to implement the operator for the following query:
>
> Select * from a left join b on a.id = b.id order by b.id;
>
> In a left outer join, I want the tuples that have matches in the inner table
> appear first. So, the order by clause is need.
Why can't you just write SELECT * FROM a LEFT JOIN b ON a.id = b.id
ORDER BY b.id NULLS FIRST? "I want my query results in a different
order" is almost never something that requires modifying the source
code.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise Postgres Company
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