Java Prevalence, is it ridiculously that simple?
There is a talk in the town, its called "Prevayler"( http://www.prevayler.org/wiki.jsp) . The idea is towards getting rid of Relational databases( Making Larry Ellison run for money) and persisting the data in-memory, yes all the data in memory. Now the claim is that its ~9000 times faster than using relational databases. Prevalyer has data objects ready to be used , meaning, you don't have to perform the object creation every time a data is being retrieved thus it saves on the costly object creation time. These objects are supposed to be cached in the same physical machine so you don't have deal with network latency and cost associated with such for database driven applications.
Folks behind this idea considers it ridiculously simple also its strange that they use the word prevalence which literally mean "Generally accepted". It is really that simple or can it be generally accepted.
I don't want to repeat what's in Prevalyer website. Prevalence folks have already figured how they can deal with system crash, backups/restore etc. What I am curious is how they are benchmarking Prevalance with relational database?
Some catchy points about Prevalance which are so debatable -->
** Rollback is needless according to prevalence. Wait a second, what about the A part solved by RDBMS in ACID, the Atomicity. I was looking for how prevalence answer my question and found that suggestion is pretty lame. Do a try and catch on your business object and have the catch remove the object graph associated so far before the exception happened. Well for first its clear that prevalence does not provide ACID and second I am not sure how you can revert from the catch block.
** Two-Phased commit is unnecessary. Well I just leave this comment to as is ...
** No SQL use OQL( Object query Language ).
In short I believe the attempt so far can be useful in using prevalence as good object caching architecture which guarantee cache recovery. But then do I need a cache database for it......
Folks behind this idea considers it ridiculously simple also its strange that they use the word prevalence which literally mean "Generally accepted". It is really that simple or can it be generally accepted.
I don't want to repeat what's in Prevalyer website. Prevalence folks have already figured how they can deal with system crash, backups/restore etc. What I am curious is how they are benchmarking Prevalance with relational database?
Some catchy points about Prevalance which are so debatable -->
** Rollback is needless according to prevalence. Wait a second, what about the A part solved by RDBMS in ACID, the Atomicity. I was looking for how prevalence answer my question and found that suggestion is pretty lame. Do a try and catch on your business object and have the catch remove the object graph associated so far before the exception happened. Well for first its clear that prevalence does not provide ACID and second I am not sure how you can revert from the catch block.
** Two-Phased commit is unnecessary. Well I just leave this comment to as is ...
** No SQL use OQL( Object query Language ).
In short I believe the attempt so far can be useful in using prevalence as good object caching architecture which guarantee cache recovery. But then do I need a cache database for it......
posted by Anand @ 11:41 AM
9 Comments:
At 2:40 AM,
Anonymous said…
Read this:
http://www.pyrasun.com/mike/mt/archives/%202004/12/index.html
Prevayler is a simple object cache blown way out of proportion by the author.
At 11:12 PM,
Anonymous said…
JoSQL does allow a SQL statement to be applied to a List of objects (I know, I wrote it!), see http://josql.sourceforge.net.
It works in a similar way to OQL but has some differences and is more designed at the Java programmer rather than sticking strictly to the "rules" of SQL (for example, JoSQL has no concept of aggregation or inner selects which seem a little pointless when dealing with objects).
I'm puzzled why the Prevlayer folks seem to prefer OQL over SQL though... (although I may be looking at the wrong tutorial for it!)
SQL is a great query language that allows you to not have to write pages of code (which is why I created JoSQL) to do the same things over and over again. JoSQL is aimed at those situations when you don't have a RDBMS available or it's too heavyweight to use one, so it may be useful for Prevlayer...
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