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plan-reading extensive tutorial?

P: n/a
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.

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TIP 9: the planner will ignore your desire to choose an index scan if your
joining column's datatypes do not match

Nov 23 '05 #1
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6 Replies

P: n/a
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.

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TIP 6: Have you searched our list archives?

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Nov 23 '05 #2

P: n/a
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

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TIP 7: don't forget to increase your free space map settings

Nov 23 '05 #3

P: n/a
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
Nov 23 '05 #4

P: n/a
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
Nov 23 '05 #5

P: n/a
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 | aj*@crankycanuck.ca

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TIP 9: the planner will ignore your desire to choose an index scan if your
joining column's datatypes do not match

Nov 23 '05 #6

P: n/a
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 | aj*@crankycanuck.ca

---------------------------(end of broadcast)---------------------------
TIP 9: the planner will ignore your desire to choose an index scan if your
joining column's datatypes do not match

Nov 23 '05 #7

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