Re: [SQL] More efficient DELETE ... ? - Mailing list pgsql-sql

From Bruce Momjian
Subject Re: [SQL] More efficient DELETE ... ?
Date
Msg-id 200001221937.OAA25487@candle.pha.pa.us
Whole thread Raw
In response to Re: [SQL] More efficient DELETE ... ?  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: [SQL] More efficient DELETE ... ?  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-sql
> The Hermit Hacker <scrappy@hub.org> writes:
> > This looks painful ...
> 
> > DELETE FROM webhit_referer_raw
> >       WHERE oid IN ( SELECT w.oid
> >                        FROM webhit_referer_raw w, referrer_data r
> >                       WHERE stat_date < 'Jan 17 2000 15:05:00'
> >                         AND w.referrer_url = r.referrer );
> 
> I believe you can do
> 
> DELETE FROM webhit_referer_raw
> WHERE referrer_url = referrer_data.referrer
>       AND referrer_data.stat_date < 'Jan 17 2000 15:05:00';
> 
> (I assume stat_date is in referrer_data, otherwise this'd be easy.)
> 
> This is an example where Postgres' willingness to create implicit FROM
> clause entries is a win ... AFAIK you couldn't do it in standard SQL,
> since for some reason DELETE doesn't take a FROM clause.

Good point.  I had forgotten all about that.

Should I cover that in my book?

What about the NOTICE we were going to add when this happens.  You will
see a WARN_FROM define in parser/*.c.  I had to disable the message
because the regression tests were failing.  They have to be regenerated
after I do this, but I can't do that here.  Do people still want the
message?  Can someone regenerate the regression output after I am done?

In fact, someone can just remove the #ifdef WARN_FROM defines around the
code and regenerate the regression tests and all will stay in sync.


--  Bruce Momjian                        |  http://www.op.net/~candle pgman@candle.pha.pa.us               |  (610)
853-3000+  If your life is a hard drive,     |  830 Blythe Avenue +  Christ can be your backup.        |  Drexel Hill,
Pennsylvania19026
 


pgsql-sql by date:

Previous
From: Web Manager
Date:
Subject: Repost: restore from dump problem - query buffer full
Next
From: gav
Date:
Subject: how many inserts in one transaction?