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[Nss-mysql-devel] [ 101504 ] id command VERY slow

From: nobody
Subject: [Nss-mysql-devel] [ 101504 ] id command VERY slow
Date: Wed, 08 Jan 2003 23:39:41 -0500

Support Request #101504, was updated on 2002-Nov-07 21:26
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Category: None
Status: Open
Priority: 5
Summary: id command VERY slow

By: kveton
Date: 2003-Jan-09 04:39
Logged In: YES 
Browser: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.3a) Gecko/20021207 

Let me guess, your tables are getting larger?  It appears
nss-mysql uses 2 left joins which are just murder for MySQL.
 The following is our query we've seen: select
site.unixname,500+site.id,"x",user.username from site LEFT
JOIN authors on site.id=500+authors.sid LEFT JOIN user on
authors.uid=user.id and 1=1 where 1 = 1 and 1=1


Any reason this can't be done with multiple selects?  3
selects would be better than this.


By: marcus
Date: 2002-Dec-09 19:54
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Browser: Mozilla/4.0 (compatible; MSIE 5.15; Mac_PowerPC)

Hi Guillaume

I did try nscd briefly, but the result of the id command 
was so slow on the first attempt (before nscd had had 
chance to cache the information), I abandoned this 
approach very quickly. Also, it would not be practical for 
me to configure it to cache user information for more 
than a few minutes, and since the system in question 
makes occassional use of many thousands of users 
(rather than frequent use of a few users), I don't think 
the effect would have been very significant.

Since our last communication, I have modified the 
system so there is now a group for every user. This has 
effectively solved the problem.

I realise now that the inefficiency is caused by nss 
rather than nss-mysql, but there is clearly an issue 
here that affects nss-mysql users. Perhaps it would be 
worth drawing this to the attention of the nss api 
developers. In the meantime, how about bundling 
some documentation with the nss-mysql distribution 
on how to maximise system speed and efficiency?

Sorry I can't contribute to the project myself - I'm only a 
lowly web developer/linux administrator!

Kindest regards


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