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Re: WO and Memory Management
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Re: WO and Memory Management


  • Subject: Re: WO and Memory Management
  • From: Chuck Hill <email@hidden>
  • Date: Fri, 14 Jul 2006 11:01:11 -0700


On Jul 14, 2006, at 10:03 AM, John Larson wrote:

Either all of your actions are a little slow or some are very slow. Sight unseen, my money is on the latter. Usually this is the result of DB access, either queries that are slow to evaluate due to missing indexes

DOH ! **Hits self in the head** Thats one thing I need to do when there DBA gets back from holidays :) We moved the DB from OpenBase to Oracle and we haven't been back an applied indexing yet : )

IMHO I wouldn't spend too much more time troubleshooting until you add the indexes to the tables. The other evidence seems to point to slow DB access and lack of indexes will only exasperate this problem. After this is fixed, then you will be in a much better position to judge the performance of the java vm and assorted processes.


As for this next statement, take it with a grain of salt, because I really don't have any evidence that this is effecting your problem. But, I had this problem when getting started with webobjects and using display groups and fetch specifications to bring in objects, then aggregating fields across all the objects in the dg or fetch spec. I had a couple of queries that would go against the db and pull in thousands of records, then build eo objects in memory, then go through all the records and sum a field value. Anyways, it was bad design on my part since I didn't understand what was going on, and I paid in all kinds of out of memory errors and affiliated problems. So, the only reason I bring that up is that it is possible for your app to get all bogged down if you are inadvertently bringing in way more records than you mean to. It can slam your db since the transaction is huge, and your VM since it is building eo instances for all the records.

An additional note on John's excellent comments: reading a large number of rows from a table will usually cause the database to escalate the row locks to a full table lock. This will then block all the other running instances. Obviously, this is not good for performance.


Wonder has a display group or a fetch iterator (my memory is a bit foggy this morning), that will allow you to fetch in batches of records without hauling in the entire result set at once. This is very useful if you don't need all the results at once.

Chuck

--
Coming sometime... - an introduction to web applications using WebObjects and Xcode http://www.global-village.net/wointro


Practical WebObjects - for developers who want to increase their overall knowledge of WebObjects or who are trying to solve specific problems. http://www.global-village.net/products/practical_webobjects




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  • Follow-Ups:
    • Re: WO and Memory Management
      • From: Guido Neitzer <email@hidden>
References: 
 >WO and Memory Management (From: Owen McKerrow <email@hidden>)
 >Re: WO and Memory Management (From: Chuck Hill <email@hidden>)
 >Re: WO and Memory Management (From: Owen McKerrow <email@hidden>)
 >Re: WO and Memory Management (From: Chuck Hill <email@hidden>)
 >Re: WO and Memory Management (From: Owen McKerrow <email@hidden>)
 >Re: WO and Memory Management (From: John Larson <email@hidden>)

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