Re: Using PDQPRIORITY to throttle certain queries

PDQ will not be used (even if set) if the query optimizer does not consider it useful. Things that will make it possibly useful are (not a full list): - Table(s) is fragmented (PDQ may allow parallel scans) - Query has ORDERS/GROUP BYs - Query plan uses several joins, table scans etc that the database may consider useful to run in parallel one thing to note, is that if you request PDQ and the engine decides to use it, you may end up with queries waiting for resources (check onstat -g mgm output). This may turn the query processing in a "sequential" process as the queries have to wait for resources (memory, scans etc.) So in general I would not use PDQ in such a scenario. I'd recommend other options: 1- Optimize the query (easier to say than to do possibly) 2- Implement some sort of replication and spread the load across other instance(s). This is easier to do if the website only "reads" 3- Check the 11.7 feature "IMPLICIT PDQ" 4- If the query uses ORDER BY make sure they're done using memory (possibly increment DS_NONPDQ_QUERYMEM) Regards. On Tue, Sep 4, 2012 at 11:48 PM, Sean Baker <SBaker@moneymailer.com> wrote: > Hoping to get some opinions on this.**** > > ** ** > > We have a public website that is currently using our main production > database (IDS 11.50.FC6). The main query used by the website uses a single > table that typically has 50K to 100K rows. The query typically completes > in 0.4 to 0.5 seconds. We ran some load tests, and if the site gets very > busy, say 20,000 requests per hour, we have some noticeable performance > degradation in the production system (mainly an OLTP system, order entry, > reporting, menu response, etc.).**** > > ** ** > > I’m not very familiar with PDQ, but a colleague suggested we could use > PDQPRIORITY to “throttle” the requests coming from the website. These are > certainly not DSS queries, so it seems to me that PDQ is not really > intended for that.**** > > ** ** > > Is “throttling” certain db queries a common use of PDQ?**** > > ** ** > > Thanks,**** > > ** ** > > Sean.**** > > _______________________________________________ > Informix-list mailing list > Informix-list@iiug.org > http://www.iiug.org/mailman/listinfo/informix-list > > -- Fernando Nunes Portugal http://informix-technology.blogspot.com My email works... but I don't check it frequently...