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Re: Fwd: Re: [PERFORM] Performance analysis of plpgsql code

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: "Karl O(dot) Pinc" <kop(at)meme(dot)com>
Cc: pgsql-patches(at)postgresql(dot)org
Subject: Re: Fwd: Re: [PERFORM] Performance analysis of plpgsql code
Date: 2005-06-29 01:53:28
Message-ID: 200506290153.j5T1rSr26346@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-patchespgsql-performance
Patch applied.  Thanks.  Your documentation changes can be viewed in
five minutes using links on the developer's page,
http://www.postgresql.org/developer/testing.


---------------------------------------------------------------------------


Karl O. Pinc wrote:
> 
> On 06/27/2005 10:03:06 PM, Karl O. Pinc wrote:
> 
> On 06/27/2005 08:34:19 PM, Michael Fuhr wrote:
> > On Tue, Jun 28, 2005 at 01:54:08AM +0000, Karl O. Pinc wrote:
> > > On 06/27/2005 06:33:03 PM, Michael Fuhr wrote:
> > >
> > > >See timeofday().
> > >
> > > That only gives you the time at the start of the transaction,
> > > so you get no indication of how long anything in the
> > > transaction takes.
> > 
> > Did you read the documentation or try it?  Perhaps you're thinking
> > of now(), current_timestamp, and friends, which don't advance during
> > a transaction; but as the documentation states, "timeofday() returns
> > the wall-clock time and does advance during transactions."
> 
> Very sorry.  I did not read through the complete documentation.
> 
> > I just ran tests on versions of PostgreSQL going back to 7.2.8 and
> > in all of them timeofday() advanced during a transaction.
> 
> For all your work a documentation patch is appended that
> I think is easier to read and might avoid this problem
> in the future.  If you don't read all the way through the
> current cvs version then you might think, as I did,
> that timeofday() is a CURRENT_TIMESTAMP related function.
> 
> Sorry, but 3 lines wrap in the patch
> in my email client.  :(
> 
> 
> Karl <kop(at)meme(dot)com>
> Free Software:  "You don't pay back, you pay forward."
>                   -- Robert A. Heinlein
> 
> 
> --- func.sgml	2005-06-26 17:05:35.000000000 -0500
> +++ func.sgml.new	2005-06-27 21:51:05.301097896 -0500
> @@ -5787,15 +5787,6 @@
>      </para>
> 
>      <para>
> -    There is also the function <function>timeofday()</function>, which  
> for historical
> -    reasons returns a <type>text</type> string rather than a  
> <type>timestamp</type> value:
> -<screen>
> -SELECT timeofday();
> -<lineannotation>Result: </lineannotation><computeroutput>Sat Feb 17  
> 19:07:32.000126 2001 EST</computeroutput>
> -</screen>
> -   </para>
> -
> -   <para>
>       It is important to know that
>       <function>CURRENT_TIMESTAMP</function> and related functions  
> return
>       the start time of the current transaction; their values do not
> @@ -5803,8 +5794,7 @@
>       the intent is to allow a single transaction to have a consistent
>       notion of the <quote>current</quote> time, so that multiple
>       modifications within the same transaction bear the same
> -    time stamp. <function>timeofday()</function>
> -    returns the wall-clock time and does advance during transactions.
> +    time stamp.
>      </para>
> 
>      <note>
> @@ -5815,6 +5805,18 @@
>      </note>
> 
>      <para>
> +    There is also the function <function>timeofday()</function> which
> +    returns the wall-clock time and advances during transactions.  For
> +    historical reasons <function>timeofday()</function> returns a
> +    <type>text</type> string rather than a <type>timestamp</type>
> +    value:
> +<screen>
> +SELECT timeofday();
> +<lineannotation>Result: </lineannotation><computeroutput>Sat Feb 17  
> 19:07:32.000126 2001 EST</computeroutput>
> +</screen>
> +   </para>
> +
> +   <para>
>       All the date/time data types also accept the special literal value
>       <literal>now</literal> to specify the current date and time.   
> Thus,
>       the following three all return the same result:
> 
> 
> ---------------------------(end of broadcast)---------------------------
> TIP 4: Don't 'kill -9' the postmaster
> 
> 
> Karl <kop(at)meme(dot)com>
> Free Software:  "You don't pay back, you pay forward."
>                   -- Robert A. Heinlein
> 
> 
> ---------------------------(end of broadcast)---------------------------
> TIP 7: don't forget to increase your free space map settings
> 

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman(at)candle(dot)pha(dot)pa(dot)us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

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