I'm migrating a SQL database of a web application to RavenDB and my team is trying to define what key generation strategy is the best for us.
The main discussion point is whether we use natural keys or surrogate keys. So I would like to know the pros and cons of each strategy in RavenDB.
Thanks
The recommended solution is to let RavenDB handles them for you.
It will generate things like "items/2", etc.
To start with, those are plenty good enough, human readable and easy to generate efficiently.
You can also do things like "users/ayende", but I would wait for that until you have more experience with RavenDB.
Finally, for advance stuff, you have keys such as "customers/1234/orders/8234" which opens up some really nice option for advanced scenarios.
If you build too much logic in your keys you may regret it later unless you know your problem domain well. We do a fair amount of RavenDB work in PHP, since there is no client. We prototype in C# then usually follow what the client creates. Sometimes the auto-pluralization's come out funny like People might be Peoples. This normally does not matter unless you are hitting RavenDB directly from Javascript. Then the only downfall is friends may question your English skills.
Related
I need a commenting system for a site I am working on. It needs to be able to be polymorphic so it can support different types of models that need comments. What would be the smarter thing to do (less code, complexity, and effort required): use Disqus, create my own system, or use some other commenting system (if you know any others please tell me)? Any advice on this topic would be much appreciated. Thanks!
Disclaimer up-front: I haven't used Disqus but they seem to be the best combination of power and effort for your needs, which are relatively straightforward. Because they are a dedicated and competent firm (and used by millions of sites) you are likely to have more features, support, and easy upgrades than if you were to build on your own.
I might have suggested a custom-built solution if your requirements were unusual in any way, but they seem to be typical for a modern commercial site. Good luck!
We are using NHibernate Search in an application which is going to be clustered.
I have been reading up on the approaches for maintaining separate collections, in particular the master/slave configuration and I was wondering how to go about implementing it using MSMQ if indeed there is an implementation for this at this time. The JMS implementation (as described in NHibernate Search in Action) seems a little daunting to me, especially as we are using a .NET environment.
Alternatively, I'm open to suggestions with regard to instantiating local RAMDirectories for the lucene collections. I know that Lucene can build a RAMDir from a FSDir and I know how to initialise an NHibernate app with a blank RAMDir but I'm getting a little lost when it comes to initialising an app with a RAMDir from an existing (network shared) FSDir.
Or indeed any other approaches.
Cheers,
Steve
I have actually recently came across this very problem. Primarily because we shared index over several webapps, for realtime updates to the indexes. However, we suffered from index corruption and couldn't really figure out why, aswell as the fact that it wouldn't work in a clustered enviroment.
My approach was this: using a service that schematically indexed new entities at very frequent intervals, aswell as reindexing everything at certain timeintervals. I also run an optimize automatically, since NHSearch doesn't seem to support auto-optimize yet.
At application start, I index everything into a RAMDirectoryProvider.
The choice you make depends highly on the data that you want to index and how sensitive you are to delays in that data, aswell as how frequent it changes. In my case, it was to allow textsearches amongst product-data for a website, so any delay was fine with me.
I did some brief research about Master-Slave providers, however I think I felt that NHSearch is rather imature as opposed to the original Java-implementation.
For me, an optimal solution would be to have a Master-Master provider, that would cross-apply all updates to the index on all nodes. I haven't research how much work it would be to write a DirectoryProvider myself, but that would be an option but much effort aswell.
I am starting to delve into the realm of ORMs, particularly NHibernate in developing .NET data-aware applications. I must say that the learning curve is pretty steep and that a lot of things should be noted. Apparently, it actually changes the way you do data-aware applications, manner of coding, development and just about everything.
Anyway, I want to ask if you do set some parameters when deciding to USE or NOT TO USE ORMs in your applications? How do you decide then the approach that one needs to make it valuable to your organization?
The organization which I work for now apparently has made a lot of SQL and Data Access thing running through back end and I must say that these class/methods/procedures have successfully performed their tasks of providing the data which is needed and when it is needed. I think it would be a tremendous effort just to map some of this into ORM and derive the same business value that the company has for the last few years.
Nevertheless, I know that ORM paves the way for applications to talk with database servers, if properly implemented. I must admit that I am at a learning stage and that I would possibly need all the help, resources and the guidance to make this transition. I was also thinking of buying the book from Manning but I feel that with so much changes to NHibernate, the book may be a bit outdated. Perhaps waiting for the Packt book on NHibernate (release on May 2010??) would help me better get up and running.
Kindly share your thoughts. By the way, if you could also point me in a small sample web app which uses NHibernate + Visual Web Developer 2008 Express and SQL Server, that would be highly appreciated.
Thanks.
For me, the short of it is the following:
If you don't use an established ORM, and you develop correctly (meaning you refactor out duplication and look to simplify where you can), you'll wind up building your own ORM through the evolution of your data access layer.
The question then becomes:
"Do I want my developers spending time learning the idiosyncrasies of my home-grown ORM or learning those of a well-documented and well-tested ORM?"
Furthermore:
"If I'm hiring a new developer, wouldn't it be nicer to bring in a developer that knows the established ORM tool we're using rather than having to train someone up on this thing I built?"
I use NHibernate, particularly Fluent - and it's great; if given the choice, I wouldn't develop on an RDBMS any other way.
To be successful with an ORM you must make sure to normalize correctly, and use the database for it's designed purpose, storing data.
I don't use an orm when:
I don't use a relation database (Relational databases are not the best choice of database for every application)
The database is has a very small amount of tables. (I might need less code without an orm)
I use a very simple database that can map to code with simple naming
conventions. (Mapping to dumb DTO classes and all queries like select * from tablename where id=#id)
Learning a good orm is worth the time and effort, it will save you writing a lot of code when you use relational databases a lot.
You can find example apps/tutorials/video's about NHibernate on with stackoverflow search. There is another book in progress by manning, maybe it's possible to read it with the early access program.
I maintain in-house business software for a living. Technologies included here are Java, Struts, Spring MVC, jsp, wicket, and a few others. I think it's time to branch out and learn something new.
I am hoping to show myself with a side project that writing code can, in fact, be fun (in some plane of the universe), and that I haven't wasted the past few years of my life doing something I can never love or have fun doing.
I'm thinking of having a fantasy-sport style web site - obviously much, much smaller with regards to features and all that. I was hoping I could get some recommendations for the newest or cleanest frameworks that will allow me to accomplish such a project. My goals are to work on following a real development process instead of just hacking a bunch of crap into an already crappy application on a daily basis. Also I will strive to follow best practices and create good, clean, understandable code that I don't shudder at the thought of having to modify. It's hard to do this at work, because the software I work on has already been developed by 50 guys from various continents that never took the time to design anything before jumping into coding.
I would need a simple database to store users and their picks for each event. Also at my job, the login security is all handled by another group completely. Do people usually write their own login systems from scratch, or are there open source utilities for that as well? I'd be interested in those, as my site will need to have a user login system, and be secure.
I had ruby and rails installed on my computer the last time I conjured up the motivation for this idea, but that was nixed by a hard drive crash. I figured before I just jumped straight to rails for this idea, that I would get a few other opinions off stack overflow to see if people liked something else that I didn't know about.
Also, if anyone has any good resources for how to think about OO design, I could brush up on that as well. I'm looking for anything that will help me to just think about the design from the start and how to get my thoughts into a diagram. I'd like it not to focus so much on patterns and other principles as much as just how to get started and actually put my thoughts in a professional document that I can use to build my project from. I tried to practice this prior to a card game that I wrote, and it got way too complicated way too fast, and the results ended up being not so great.
I’m more familiar with Django, although like you, the only frameworks I’ve really used are the Java/Struts/Spring/JSP, etc. The automatically generated administration interface in Django is amazing coming from these, and it comes with its own authentication system too.
Unless you’re especially predisposed against Python, I think you should give it a go.
Ruby on Rails, Python on Django, PHP on (not sure -- maybe Zend? or CakePHP?), are probably the most popular frameworks if I understand correctly that you want to learn a new language. If I misunderstood you, and you'd rather stick with Java, GWT seems pretty cool -- it's the only real way to avoid "explicitly" writing Javascript (if you DO want to learn and use some Javascript, I personally am in love with Dojo, but jQuery is substantially more popular: those are two good popular frameworks you should consider, though there are others of course, like for all languages I mentioned so far).
One advantage of picking Python and Django is that they work particularly well with Google App Engine (and with Dojo, too, thanks to the cool dojango project!) -- GAE supports JVM too, now, but it's supported Python for a much longer time and the Python side of it is more solid and complete at this time. So, if that's the technology stack you choose, you get to develop and deploy for free, on highly scalable infrastructure, at least until your app gets more than a few million page views per month -- and you really minimize your system adminsitration hassles, all you do is basically to code and write one simple configuration file.
I am really torn right now between using O/R mappers or just sticking to traditional data access. For some reason, every time I bring up O/R mappers, fellow developers cringe and speak about performance issues or how they're just bad in general. What am I missing here? I'm looking at LINQ to SQL and Microsoft Entity Framework. Is there any basis to any of these claims? What kind of things do I have to compromise if I want to use an O/R mapper. Thanks.
This will seem like an unrelated answer at first, but: one of my side interests is WWII-era fighter planes. All of the combatant nations (US, Great Britain, Germany, USSR, Japan etc.) built a bunch of different fighters during the war. Some of them used radial engines (P47, Corsair, FW-190, Zero); some used inline liquid-cooled engines (Bf-109, Mustang, Yak-7, Spitfire); and some used two engines instead of one (P38, Do-335). Some used machine guns, some used cannons, and some used both. Some were even made out of plywood, if you can imagine.
In the end, they all went really really fast, and in the hands of a competent, experienced pilot, they would shoot your rookie ass down in a heartbeat. I don't imagine many pilots flew around thinking "oh, that idiot is flying something with a radial engine - I don't have to worry about him at all". Everyone understood that there were many different ways of achieving the ultimate goal, and each approach had its particular advantages and disadvantages, depending on the circumstances.
The debate between ORM and traditional data access is just like this, and it behooves any programmer to become competent with both approaches, and choose the option that is right for the job at hand.
I struggled with this decision for a long time. I think I was hesitant for two primary reasons. First, O/R mappers represented a lack of control over what was happening in a critical part of the app and, second, because so many times I've been disappointed by solutions that are awesome for the 90% case but miserable for the last 10%. Everything works for select * from authors, of course, but when you crank up the complexity and have a high-volume, critical system and your career is on the line, you feel you need to have complete control to tune every query pattern and byte over the wire. Most developers, including me, get frustrated the first time the tool fails us, and we cannot do what we need to do, or our need deviates from the established pattern supported by the tool. I'll probably get flamed for mentioning specific flaws in tools, so I'll leave it at that.
Fortunately, Anderson Imes finally convinced me to try CodeSmith with the netTiers template. (No, I don't work for them.) After more than a year using this, I can't believe we didn't do it sooner. My team uses Visual Studio DB Pro, and on every check-in our continuous integration build drops out a new set of data access layer assemblies. This handles all the common, low risk stuff automatically, yet we can still write custom sprocs for the tricky bits and have them included as methods on the generated classes, and we can customize the templates for the generated code as well. I highly recommend this approach. There may be other tools that allow this level of control as well, and there is a newer CodeSmith template called PLINQO that uses LINQ to SQL under the hood. We haven't that yet examined (haven't needed to), but this overall approach has a lot of merit.
Jerry
O/RM tools designed to perform very well in most situations. It will cache entities for you, it will execute queries in bulks, it has a very low level optimised access to objects which is way faster than manually assigning values to properties, they give you a very easy way to incorporate variations of aspect oriented programming using modern technics like interceptors, it will manage entity state for you and help resolve conflicts and many more.
Now cons of this approach usually lies in lack of understanding of how things work on a very low level. Most classic problem is "SELECT N+1" (link).
I've been working with NHibernate for 2.5 years now, and I'm still discovering something new about it almost on a daily basis...
Good. In most cases.
The productivity benefit of using an ORM, will in most case outweigh the loss of control over how the data is accessed.
There are not that many who would avoid C#, in order to program is MSIL or Assembly, although that would give them more control.
The problem that i see with a lot of OR mappers is that you get bloated domain objects, which are usually highly coupled with the rest of your data access framework. Our developers cringe at that as well :) It's just harder to port these object to another data access technology. If you use L2S, you can take a look at the generated code. It looks like a complete mess. NHibernate is probably one of the best at this. Your entities are completely unaware of your data access layer, if you design them right.
It really depends on the situation.
I went from a company that used a tweaked out ORM to a company that did not use a ORM and wrote SQL queries all the time. When I asked about using an ORM to simplify the code, I got that blank look in the face followed by all the negatives of it:
Its High Bloat
you don't have fine control over your queries and execute unnecessary ones
there is a heavy object to table mapping
its not dry code because you have to repeat your self
on an on
Well, after working there for a few weeks, I had noticed that:
we had several queries that were almost identical, and alot of times if there was a bug, only a handful would get fixed
instead of caching common tables queries, we would end up reading a table multiple times.
We were repeating our selves all over the place
We had several levels of skill level, so some queries were not written the most efficiently.
After I pointed most of this out, they wrote a "DBO" because the didn't want to call it an ORM. They decided to write one from scratch instead of tweaking out one.
Also, alot of the arguments come from ignorance against ORM's I feel. Every ORM that I have seen allows for custom queries, and even following the ORM's conventions, you can write very complex and detailed queries and normally are more human readable. Also, they tend to be very DRY, You give them your schema, and they figure the rest out, down to relationship mapping.
Modern ORM's have a lot of tools to help you out, like migration scripts, multiple DB types accessed to the same objects so you can leverage advantages of both NOSQL and SQL DB's. But you have to pick the right ORM for your project if your going to use one.
I first got into ORM mapping and Data Access Layers from reading Rockford Lhotka's book, C# business objects. He's spent years working on a framework for DAL's. While his framework out of the box is quite bloated and in some cases, overkill, he has some excellent ideas. I highly recommend the book for anyone looking at ORM mappers. I was influenced by his book enough to take away a lot of his ideas and build them into my own framework and code generation.
There is no simple answer to this since each ORM provider will have it's own particular pluses and minuses. Some ORM solutions are more flexible than others. The onus is on the developer to understand these before using one.
However, take LinqToSql - if you are sure you are not going to need to switch away from SQL Server then this solves a lot of the common problems seen in ORM mappers. It allows you to easily add stored procedures (as static methods), so you aren't just limited to generated SQL. It uses deferred execution, so that you can chain queries together efficiently. It uses partial classes to allow you to easily add custom logic to generated classes without needing to worry about what happens when you re-generate them. There is also nothing stopping you using LINQ to create your own, abstracted DAL - it just speeds up the process. The main, thing, though is that it alleviates the tedium and time required to create basic CRUD layer.
But there are downsides, too. There will be a tight coupling between your tables and classes, there will be a slight performance drop, you may occasionally generate queries that are not as efficient as you expected. And you are tied in to SQL Server (though some other ORM technlogies are database agnostic).
As I said, the main thing is to be aware of the pros and cons before pinning your colours to a particular methodology.