5 important questions
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5 important questions
by Daniel Lanciana
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Hi,
Below are my only 5 concerns about using Prevayler. I hope there are solutions for all of them... 1. Can Prevayler data cannot be exposed to any applications other than the original Java app (e.g. a client desktop .NET program or visualisation tools)? If so, is it supported "out of the box" so to speak? 2. What visualisation tools (i.e. navicat) are available for browsing/modifying Prevayler data? 3, How do you know when more RAM is needed? Does everyone need to set up their own monitoring? 4. How well does Prevayler perform with queries such as "all managers earning over $50,000 with a surname starting with 'K'"? I'm especially interested in the performance of wildcards (SQL LIKE operator). 5. How easy is it to refactor a POJO (e.g. add or remove a property)? A step-by-step would be useful. Cheers, Daniel. ------------------------------------------------------------------------------ _______________________________________________ To unsubscribe go to the end of this page: http://lists.sourceforge.net/lists/listinfo/prevayler-discussion _______________________________________________ "Databases in Memoriam" -- http://www.prevayler.org |
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Re: 5 important questions
by Diego Miranda
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Hi Daniel,
2. What visualisation tools (i.e. navicat) are available for browsing/modifying Prevayler data? What do you mean with Prevayler data? With Prevayler your data is your object graph. 4. How well does Prevayler perform with queries such as "all managers earning over $50,000 with a surname starting with 'K'"? I'm especially interested in the performance of wildcards (SQL LIKE operator). To perform queries you can use JXPath (http://commons.apache.org/jxpath/) or take a look at NoDB (http://nodb.googlecode.com/) I think i don't understand points 1 and 5. Best Regards Diego -- Ley de Hofstadter: Siempre toma más tiempo del que se preveía, aun cuando se tenga en cuenta la Ley de Hofstadter. ------------------------------------------------------------------------------ _______________________________________________ To unsubscribe go to the end of this page: http://lists.sourceforge.net/lists/listinfo/prevayler-discussion _______________________________________________ "Databases in Memoriam" -- http://www.prevayler.org |
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Re: 5 important questions
by Daniel Lanciana
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Hi,
I'll elaborate (using the word "data" to represent the saved object graph): 1. Imagine two web servers, Tomcat and Apache HTTP. Tomcat has a web application using Prevayler, Apache HTTP has a web application in PHP. How do I access the live Tomcat "data" from the second web server (in PHP)? Manually created web services? 2. What administration/visualisation tools (i.e. Navicat) are available from browsing/modifying the object graph "data"? Example: Browsing a user's payment object and manually changing the reference number. 3, How do you know when more RAM is needed? Does everyone need to set up their own monitoring? 4. Are there any benchmarks on how well Prevayler performs with queries such as "all managers earning over $50,000 with a surname starting with 'K'"? I'm especially interested in the performance of wildcards (SQL LIKE operator). The benchmark would need to be suitably complex with a few thousand records. 5.Example: There is a web application using Prevayler in production. A new field, "referrer", needs to be added to the User POJO. Do I just add the new field to the POJO and restart the web application? Will it automatically convert all the previously saved User objects (no referrer field) to the new User object? If not, please describe what steps would need to be done. Hope that clears some things up. Regards, Daniel. On Sat, Jul 4, 2009 at 3:09 PM, Diego Miranda <diego.miranda@...> wrote: Hi Daniel, ------------------------------------------------------------------------------ _______________________________________________ To unsubscribe go to the end of this page: http://lists.sourceforge.net/lists/listinfo/prevayler-discussion _______________________________________________ "Databases in Memoriam" -- http://www.prevayler.org |
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Re: 5 important questions
by Ralph Johnson
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On Sun, Jul 5, 2009 at 6:25 AM, Daniel
Lanciana<daniel.lanciana@...> wrote: > 1. Imagine two web servers, Tomcat and Apache HTTP. > Tomcat has a web application using Prevayler, Apache HTTP has a web > application in PHP. > How do I access the live Tomcat "data" from the second web server (in PHP)? > Manually created web services? Perhaps you can't. Usually the only way to accept the data in Prevaylor is to go through your Java app. If you make a web service out of your app then the PHP could access the data that way. But the PHP is not going to access the database directly. If you want to use your database for application integration, don't use Prevalor. On the other hand, if you want to integrate through web services, Prevaylor might work very well. > 3, How do you know when more RAM is needed? Does everyone need to set up > their own monitoring? My rule of thumb is that if a system pages, it needs more memory. So, use a utility that tells you how much the operating system is paging. A Prevayler-type system only works well if all the data fits in memory. > 5.Example: There is a web application using Prevayler in production. A new > field, "referrer", needs to be added to the User POJO. > Do I just add the new field to the POJO and restart the web application? > Will it automatically convert all the previously saved User objects (no > referrer field) to the new User object? If not, please describe what steps > would need to be done. Any Prevayler-type system needs a way of storing data on the disk. When you boot up the system, it will read in all the data, and thereafter access the in-memory version of the data. When you change your schema, you have to change the program that reads in the data so it can handle old data formats. Usually this is easy, but sometimes it is hard. In this case, you have to define a default referrer for all the old data objects, since they won't have a referrer field. -Ralph Johnson ------------------------------------------------------------------------------ _______________________________________________ To unsubscribe go to the end of this page: http://lists.sourceforge.net/lists/listinfo/prevayler-discussion _______________________________________________ "Databases in Memoriam" -- http://www.prevayler.org |
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Re: 5 important questions
by Klaus Wuestefeld
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"Does Prevayler provide this? Does Prevayler provide that?"
The only thing Prevayler provides is invulnerability for you business objects. All other things you must/can do as if accessing POJOs in RAM. No more, no less. > When you change > your schema, you have to change the program that reads in the data so > it can handle old data formats. Usually this is easy, but sometimes > it is hard. In this case, you have to define a default referrer for > all the old data objects, since they won't have a referrer field. To add or remove a field is easy. Your new class just has to declare a static serialVersionUUID field (google it) with the same value as the old and Java serialization will read the old state in without any problem. I just put serialVersionUUID = 1 on all my serializable classes and forget about it. Hard things are splitting a class in two, changing the superclass, etc... For that you have to write custom code. See you, Klaus. ------------------------------------------------------------------------------ _______________________________________________ To unsubscribe go to the end of this page: http://lists.sourceforge.net/lists/listinfo/prevayler-discussion _______________________________________________ "Databases in Memoriam" -- http://www.prevayler.org |
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