Re: Antwort: Re: howto implement a fifo queue in MySQL Cluster ?

[Martin Skold]

Hi!

How exactly are the INSERT statements done?
How many clients?

BR
-- Martin

Hendrik Woltersdorf wrote:
> Hi,
> 
> I have already set ndb_autoincrement_prefetch_sz to 1. It does not force 
> order.
> What I get is this:
> 
> ID DATE_INSERT
> -------------------------------------
> 14757, '2010-01-29 10:15:51'
> 14756, '2010-01-29 10:15:50'
> 14755, '2010-01-29 10:15:50'
> 14721, '2010-01-29 10:15:50'
> 14720, '2010-01-29 10:15:50'
> 14719, '2010-01-29 10:15:50'
> 14739, '2010-01-29 10:13:37'
> 14738, '2010-01-29 10:13:37'
> 14737, '2010-01-29 10:13:37'
> 14736, '2010-01-29 10:13:37'
> 
> kind regards
> 
> Hendrik Woltersdorf
> XCOM AG
> Tel.: [phone]
> Tel. mobil: 0178/5710078
> Email: Hendrik.Woltersdorf@stripped
> 
> Inactive hide details for Martin Skold ---29.01.2010 
> 11:14:58---Hi!Martin Skold ---29.01.2010 11:14:58---Hi!
> 
>                         *Martin Skold <Martin.Skold@stripped>*
>                         Gesendet von: Martin.Skold@stripped
> 
>                         29.01.2010 11:13
> 
> 	
> 
> An
> 	
> Hendrik Woltersdorf <hendrik.woltersdorf@stripped>
> 
> Kopie
> 	
> cluster@stripped
> 
> Thema
> 	
> Re: howto implement a fifo queue in MySQL Cluster ?
> 
> 	
> 
> 
> Hi!
> 
> Autoincrement values are inserted in order, but we prefetch
> series of values to get better performance. So if you are
> inserting from several connections (or mysqld's) you will
> not get a total ordering. If you want that you can set
> ndb_autoincrement_prefetch_sz to 1 should force order.
> This will, however, degrade performance for inserts.
> 
> BR
> -- Martin
> Hendrik Woltersdorf wrote:
>  > Hi all,
>  >
>  > how do I implement a fifo queue in MySQL Cluster ?
>  >
>  > What I want to do:
>  >
>  > I write inserts and updates to some tables with triggers into a queue.
>  > These rows have to be read and processed in chronological order.
>  > My first attempt was to use a table with an autoincrement column as the
>  > primary key. But tests show, that these autoincrement values are not
>  > inserted in chronological order. A datetime column does not help either,
>  > because it is by far not precise enough, and it depends on the
>  > synchronization of the clocks of the different sql node machines.
>  >
>  > Any ideas, how to read these data rows in chronological order ?
>  >
>  > The second best idea is, to use "select max(PK)+1", but this will cause
>  > lots of duplicate key errors.
>  >
>  > I am using MySQL Cluster version 7.0.7 with 2 data nodes, 2 management
>  > nodes and 2 sql nodes.
>  >
>  > kind regards
>  >
>  > Hendrik Woltersdorf
>  > XCOM AG
>  > Tel.: [phone]
>  > Tel. mobil: 0178/5710078
>  > Email: Hendrik.Woltersdorf@stripped
>  >
>  >
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> This email may contain material that is confidential and for the sole 
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> forwarding without express permission is strictly prohibited. If you are 
> not the intended recipient, please contact the sender and delete all copies.
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> Hauptsitz: Bahnstrasse 37, D-47877 Willich, USt-IdNr.: DE 812 885 664
> Kommunikation: Telefon [phone], Telefax [phone], 
> www.xcom.de
> Handelsregister: Amtsgericht Krefeld, HRB 10340
> Vorstand: Matthias Albrecht, Marco Marty, Dr. Rainer Fuchs, Dirk Werner
> Vorsitzender des Aufsichtsrates: Stefan H. Tarach
>