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#1: are concurent queries serialized ?

Posted on 2005-09-29 00:25:33 by pierre.bru

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hi,
=20
I run a web server on a linux box from which PHP connect to a mySQL 4 =
server running on another linux box.
tis works well but when the number of concurent connection/queries go =
high, the DB server runs very slowly.
=20
while trying to find a fix to this problem, I've been told that whatever =
the number of concurent queries the DB server receive, it process them =
thru a queue, that no more than 1 query may be performed by mySQL at a =
time.
=20
is this true ?
=20
true or not, will I gain speed by by preventing the web server to =
perform too many connections/queries at the same time? I mean, will =
10000 connection/queries be executed faster if there is at most 25 =
concurent queries than if there are 100 or more concurent =
connections/queries? (by queries, I mean a mix of select (lot) and =
update (few))
=20
TIA,
Pierre.

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#2: Re: are concurent queries serialized ?

Posted on 2005-09-29 22:05:11 by Gleb Paharenko

Hello.



At first, you should find out the root of the problem. Use 'SHOW

PROCESSLIST' or mysqladmin processlist (-i 1 -r options might be

helpful). See:

http://dev.mysql.com/doc/mysql/en/show-processlist.html



>1 query may be performed by mySQL at a time.

>is this true ?



It depends. But in general it is not true. InnoDB for example allows

a great concurrency. See:

http://dev.mysql.com/doc/mysql/en/innodb.html





>hi,

>

>I run a web server on a linux box from which PHP connect to a mySQL 4

server ru

nning on

>another linux box.

>tis works well but when the number of concurent connection/queries go

high, the

DB server

>runs very slowly.

>

>while trying to find a fix to this problem, I've been told that

whatever the nu

mber of

>concurent queries the DB server receive, it process them thru a queue,

that no

more than

>1 query may be performed by mySQL at a time.

>

>is this true ?

>

>true or not, will I gain speed by by preventing the web server to

perform too m

any

>connections/queries at the same time? I mean, will 10000

connection/queries be

executed

>faster if there is at most 25 concurent queries than if there are 100

or more c

oncurent

>connections/queries? (by queries, I mean a mix of select (lot) and

update (few)

)

>



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