Thread: plan-reading extensive tutorial?

plan-reading extensive tutorial?

From
Klint Gore
Date:
In the docs it says "Plan-reading is an art that deserves an extensive
tutorial, which this is not".  Is there one?  I've gone beyond simple
queries (which are performing well) to the more difficult queries (which
aren't).

e.g. 4 generation family tree implemented as a view using 14 left outer
joins back into the same table. If I select only from it, the optimizer
uses the primary key (single int4 field) in nested loop left join on all
14.  If I join the view to another table, it wants to do it sequentially
(the other table is just a single int4 field with 1 row. the field is
the primary key and also has a foreign key constraint to the main table).

I dont want exact help on this particular query.  Posting every query
I'm having a problem with to the mailing list is a waste of both my time
and yours (and not really feasable since it requires all the table
structures and data).  I have tried the obvious with vacuum full
analyze,  and changing the settings (like enable_seqscan,
join_collapse_limit, from_collapse_limit...).

klint.

+---------------------------------------+-----------------+
: Klint Gore                            : "Non rhyming    :
: EMail   : kg@kgb.une.edu.au           :  slang - the    :
: Snail   : A.B.R.I.                    :  possibilities  :
: Mail      University of New England   :  are useless"   :
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: Fax     : +61 2 6772 5376             :                 :
+---------------------------------------+-----------------+

Re: plan-reading extensive tutorial?

From
Chris
Date:
On Mon, 2004-04-19 at 08:35, Klint Gore wrote:
> In the docs it says "Plan-reading is an art that deserves an extensive
> tutorial, which this is not".  Is there one?  I've gone beyond simple
> queries (which are performing well) to the more difficult queries (which
> aren't).

Red Hat has a tool called "Visual explain" that shows explain output
graphically:

http://sources.redhat.com/rhdb/

It might help understand what's going on.


Bye, Chris.



Re: plan-reading extensive tutorial?

From
Shridhar Daithankar
Date:
Klint Gore wrote:

> In the docs it says "Plan-reading is an art that deserves an extensive
> tutorial, which this is not".  Is there one?  I've gone beyond simple
> queries (which are performing well) to the more difficult queries (which
> aren't).

Try this one..

http://www.gtsm.com/oscon2003/toc.html

  Shridhar

Re: plan-reading extensive tutorial?

From
"Gregory S. Williamson"
Date:
FWIW, this site gives:
404 - File Not Found

     "These aren't the droids files you're looking for."

Sorry, but that file could not be found. And believe you me, we looked! We checked all the likely directories, then all
theunlikely directories, and even grepped 
through the RAM. We broke into all the computers on our nearby subnet and checked their directories, but still could
notfind anything. We checked underneath the 
cushions, but all we turned up was that remote we've been looking for since last year. We searched through the laundry
bin,rummaged through the junk drawer, and 
even asked the neighbor if they had a copy (like they would tell us anyway - they still haven't returned that
index.htmlwe loaned them 3 weeks ago!) Are you really, 
really sure that's the correct file?

[which is a lot better than the usual 404 message, you have to admit!]

Greg Williamson
DBA
GLobeXplorer LLC

-----Original Message-----
From: Shridhar Daithankar [mailto:shridhar@frodo.hserus.net]
Sent: Monday, April 19, 2004 1:39 AM
To: Klint Gore
Cc: pgsql-general@postgresql.org
Subject: Re: [GENERAL] plan-reading extensive tutorial?


Klint Gore wrote:

> In the docs it says "Plan-reading is an art that deserves an extensive
> tutorial, which this is not".  Is there one?  I've gone beyond simple
> queries (which are performing well) to the more difficult queries (which
> aren't).

Try this one..

http://www.gtsm.com/oscon2003/toc.html

  Shridhar

---------------------------(end of broadcast)---------------------------
TIP 7: don't forget to increase your free space map settings

Re: plan-reading extensive tutorial?

From
Andreas
Date:
Gregory S. Williamson schrieb:

>FWIW, this site gives:
>404 - File Not Found
>[...]
>[which is a lot better than the usual 404 message, you have to admit!]
>
>
No doubt :)
... but simply clicking on the url you provided in your mail led to the
document.

> <>[...]
> http://www.gtsm.com/oscon2003/toc.html



Re: plan-reading extensive tutorial?

From
"scott.marlowe"
Date:
On Mon, 19 Apr 2004, Gregory S. Williamson wrote:

> FWIW, this site gives:
> 404 - File Not Found
>
>      "These aren't the droids files you're looking for."
>
> Sorry, but that file could not be found. And believe you me, we looked! We checked all the likely directories, then
allthe unlikely directories, and even grepped 
> through the RAM. We broke into all the computers on our nearby subnet and checked their directories, but still could
notfind anything. We checked underneath the 
> cushions, but all we turned up was that remote we've been looking for since last year. We searched through the
laundrybin, rummaged through the junk drawer, and 
> even asked the neighbor if they had a copy (like they would tell us anyway - they still haven't returned that
index.htmlwe loaned them 3 weeks ago!) Are you really, 
> really sure that's the correct file?
>
> [which is a lot better than the usual 404 message, you have to admit!]

My favorite is:

http://www.shartwell.freeserve.co.uk/humor-site/404server.htm



Re: plan-reading extensive tutorial?

From
Jeff Boes
Date:
Chris wrote:
> Red Hat has a tool called "Visual explain" that shows explain output
> graphically:
>
> http://sources.redhat.com/rhdb/
>

I'm having a devil of a time getting this installed on my system ...
anybody here willing to give me a walk-through?


--
Jeff Boes                                      vox 269.226.9550 ext 24
Database Engineer                                     fax 269.349.9076
Nexcerpt, Inc.                                 http://www.nexcerpt.com
            ...Nexcerpt... Extend your Expertise

Re: plan-reading extensive tutorial?

From
Andrew Sullivan
Date:
On Tue, Apr 20, 2004 at 05:44:53PM +0000, Jeff Boes wrote:
>
> I'm having a devil of a time getting this installed on my system ...
> anybody here willing to give me a walk-through?

I did it just yesterday, to show it to someone.  What's the problem?
Do you have the proper jdk and ant?  Are they first in your $PATH?  I
know that on debian, for instance, when you type 'java' you get
something that's free but which doesn't always work.

--
Andrew Sullivan  | ajs@crankycanuck.ca