I want to persist objects into Isolated Storage, so far I could think of these ways:
Serialize them into an xml file when saving and then serialize them back when saving.
Use an Object DB. Doubt abounds about a good or recommended one (Examples are Perst, winphone7db and Sterling DB)
Anyone can suggest some best practices?
As a basic guideline:
If you need the functionality of a database (relations, transactions, search, etc.) then you should use a database.
If you just need an object store, then you should just save your objects into Isolated Storage directly (serialising where necessary).
I haven't used each of the different DB options available but would probably go with Perst as it's the most established (there's also a good guide here), winphone7db is also not available yet.
Related
We have various windows services that load up a large amount of data i.e. mostly settings, from a database into an object which is used whenever calls are made to our various .net remoting functions (I know it's old!!). Having this object containing all these settings in memory saves us having the query the database constantly or load the data from a cache whenever queries are executed.
Settings in this "large" object are collections of data, from id, path, text, etc...
We want to move away from .net remoting to wcf and potentially get rid of our windows services and run the lot under IIS (and eventually Azure), but being stateless, I'm wondering how should we handle this?
1) What's the best method you can think of? From experience preferrably.
One suggestion that was made to me was to return all of this to the client, cache it and use only the relevant settings when making a wcf call.
2) Numerous services we have are polling services, constantly monitoring, databases, file locations, ftp locations, etc... How would you recommend to handle this in a stateless environment?? I can't see how this will be handled.
We use SQL Server, but I don't want to rely too heavily on the build-in features as we could potentially have to suppor the likes of mySQL & Oracle.
Thanks.
Thierry
You could store these settings in the AppSettings section of the config file (Web.config for IIS). Using the ConfigurationManager class, you can retrieve the relevant values as needed.
If you prefer to store a static instance of your settings object, suggest implementing a Singleton pattern for the same. Jon Skeet's article is a great starting point.
Hope this helps.
I am unsure of the mongolitedb persistence lifecycle on the client-side. Is it possible to store binary data in there and later reference in html? Or perhaps the best way is to use html5 persistence through localstorage. Any thoughts or suggestions?
The amplify package gives a nice interface for localStorage. Minimongo doesn't persist anything on the client. It's only stored in memory. If you want to persist some of the documents in local storage you'll need to do it yourself for now.
Say I have some objects that need to be created only once in the application yet accessed from within multiple requests. The objects are immutable. What is the best way to do this?
Store them in the session.
If you don't want to lose them after a server's restart, then use a database (SQLite, which is a single file, for example).
You want to persist your objects. Normally you'd do it with some ORM like Active Record or Datamapper. Depending on what is available to you. If you want something dead simple without migrations and you have access to a MongoDB use mongomapper.
If that object is used only for some time, then it is discarded (and if needed again, then recreated), use some caching mechanism, like memcached or redis.
If setting up such services is heavy and you want to avoid it, and - say - you are using Debian/Ubuntu then save your objects into files (with Marshal-ing) in the /shm device which is practically memory.
If the structure of the data is complex, then go with SQLite as suggested above.
We are designing our new product, which will include multi-tenancy. It will be written in ASP.NET and C#, and may be hosted on Windows Azure or some other Cloud hosting solution.
We’ve been looking at MVC and other technologies and, to be honest, we’re getting bogged down in various acronyms (MVC, EF, WCF etc. etc.).
A particular requirement of our application is causing a headache – the users will be able to add fields to the database, or even create a whole new module.
As a result, each tenant would have a database with a different structure to every other tenant using the system. We envisage that every tenant will have their own database, rather than sharing a database.
(Adding fields etc. to the system will be accomplished using a web interface).
All well and good, but the problem comes when creating a data model for MVC. Modifying a data model programmatically to add a field to a table seems to be impossible, according to this link:
Create EDM during runtime?
This is a major headache for us. Even if we don’t use MVC, I think we’d still want to create a data model (perhaps for used with LINQ to SQL).
We’re considering having a table with loads of fields in it, and instead of adding fields to the database we allocate an existing field in the table when the user wants to add a field to his form. Not sure I like that idea, though.
Of course, we don’t have to use MVC or Entity Framework, but it appears to me that these are the kind of technologies that Microsoft would steer us towards for future development.
Any thoughts? I’m assuming that we’re not the first people in the world to consider this idea of a user-customisable application.
I'd make sure that you have fully explored the option of creating 'Name-Value Pair' type tables as described here http://msdn.microsoft.com/en-us/library/aa479086.aspx#mlttntda_nvp
before you start looking at a customizable schema. Also don't forget that you are going to have to grant much higher permissions to your sql accounts in order for them to create tables on the fly.
A customizable schema means that your sql accounts will also need much higher permissions. It wouldnt be advisable to assign these higher permissions to a tenants account, but to a separate provisioning account which can perform these tasks.
Also before investing effort into EF - try googling 'EF Vote of No Confidence'. It was raised (i believe) mainly in reaction to earlier versions but its definately worth reading up on. nHibernate is an alternative worth investigating.
Just off the top of my head it sounds like a bad idea to allow users to change the database schema. I think you are missing a layer of abstraction. In my mind, it would be more correct to use the database to hold data that describes the format of a customer's data. The actual data would then be saved in a text column as xml, including version information.
This solution may not fit your needs, but I don't know the details of your project. So just consider it my 5 cents.
Most modern SQL databases today supports the 'jsonb' type for key/value storage as a field. Other types (hstor for postgres) exists too. Forget about XML, that's yesterday and no application with respect for itself implements XML unless it is for importing/converting old data.
I've found no clear answer so far, but maybe I've searched the wrong way.
My Question is, can Core Data to be used as a Persitence Storage for a Server Project? Where are Core Data's Limits, how much Data can be handled with Core Data and SQLite? SQLite should handle a lot of Data very well according to their website. I know of a properitary Java Persitence Manager with an Oracle DB as Storage that handles Millions of Entries and 3000 Clients without Problems. For my own Project I wonder if I can use Core Data on the Server Side for User Mangament and intern microblogging, texting with up to 5000 clients. Will it handle such big amounts of Data or do I have to manage something like that myself? Does anyone happend to have experience with huge amounts if Data and Core Data?
Thank you
twickl
I wouldn't advise using Core Data for a server side project. Core Data was designed to handle the data of individual, object-oriented applications therefore it lacks many of the common features of dedicated server software such as easily handling multiple simultaneous accesses.
Really, the only circumstance where I would advise using it is when the server side logic is very complex and the number of users small. For example, if you wanted to write an in house web app and have almost all the logic on the server, then Core Data might serve well.
Apple used to have WebObjects which was a package to manage servers using an object-oriented DB much like Core Data. (Core Data was inspired by a component of WebObjects called Enterprise Objects.) However, IIRC Apple no longer supports WebObjects for external use.
Your better off using one of the many dedicated server packages out there than trying to roll your own.
I have no experience using Core Data in the manner you describe, but my understanding of the architecture leads me to believe that it could be used, depending on how you plan to query and manipulate the data.
Core Data is very good at maintaining an object graph and using faults to bring parts into memory as needed. In that manner, it could be good on a server for reducing memory requirements even with a large data set.
Core Data is not very good at manipulating collections of objects without loading them into memory, making a change, and writing them back out to disk. Brent Simmons wrote a blog post about this, where he decide to stop using Core Data for some of his RSS reader's model objects because an operation like "mark all as read" didn't scale. While you would like to be able to say something like UPDATE articles SET status = 'read', Core Data must load each article, set its status property, then write it back to disk.
This isn't because Apple engineers are stupid, but because the query layer can't make assumptions about the storage layer (you could be using XML instead of SQLite) and it also must take into account cascading changes and the fact that some article objects may already be loaded into memory and will need to be updated there.
Note that you can also write your own storage providers for Core Data, see Aaron Hillegass's BNRPersistence project. So if Core Data was "mostly good" you might be able to improve on it for your application.
So, a possible answer to your question is that Core Data may be appropriate to your application, as long as you do not need to rely on batch updates to large number of objects. In general, no algorithm or data structure is appropriate for every scenario. Engineering is about wisely choosing between trade-offs. You won't find anything that works well for many clients in every case. It always matters what you are doing.