I'm involved in a project thats going to be developing a mobile application which will be interacting with a remote database. I'm wondering what the best way to design the interaction between these devices and the database will be, to make best use of battery life, bandwidth etc.
Should we have a server side application/set of scripts which do all the database interaction and then send the data back to our application as XML in a response, or should we have the devices querying the database directly? Or is there another better way to approach this?
My feeling atm is that the former will be a bit more work, but will reduce the workload on the devices, saving power etc, which would be a better way to go.
Thanks!
What do you mean by "have the devices querying the database directly". It is normally considered a bad idea (for security reasons) to expose your database server directly to the Internet. The standard approach is to provide Web Services that connect to the database and return data as JSON or some other format.
Performance is a big issue with these devices and I have found that they are very slow to process XML so you may be better to try using JSON. Also I suggest to stay clear of data sets and data tables. Collections of plain business objects run much faster.
You might want to have a look at this:
What are the most valuable .Net Compact Framework Tips, Tricks, and Gotcha-Avoiders?
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I have a node.js application that uses a MySQL database. I wanted to know what would be a good place for storing the sessions?
My application is actually a final project for one of my courses, but it could be a real world application later, as we are re-writing a software that is currently used by the university. I can use MySQL for session store, but I want to make my application using the most reliable or best practice in my situation.
I have read many posts/answers/forums, and the opinion is divided. Using another technology like Memcached/MemcacheDB or Redis, just for session store, would it be a recommended approach? Or should I just stick to MySQL, and later deal with scaling if the server load increases?
Even if the application is later used in real world, it would only be used by the undergraduate university students and faculties, so the users are sort of limited.
As of now, I'm leaning towards MySQL for the session store.
I am replying under the assumption that you are using MySQL throughout the whole application.
If the application will be used in the context of your university possibly it will not have scaling issues. SQL databases are not bad, they are able to handle quite a lot of data efficiently, you just need to be careful in the first place and to create efficient queries. Be careful with the joins because can really kill the server. You need to analyze quite a lot your application. For example, why do you think that you will have scaling/performance issues on the sessions and not in another place of your application? Do a bit of load testing, get some metrics and try to understand if you need it or no.
If you are a student though and you don't have prior experience with redis, I would go with redis because it is good to work with a new technology and gain a bit more of experience :)
I am currently looking into making a basic video game.
I have programming knowledge in Web technology, but not much in Android so I am most likely going to start by making a Web app on Android.
I haven't used Web storage much in the past, but I do know about local storage and indexed db, which could be considered as a way to store data, but this kind of data seems too easy to delete by mistake because people just generally wipe out Web data once in a while without filtering out important data.
What is the most appropriate way to store Web app game data?
The storage type relies on the characteristics of the data.
If you want to store small amount of data in key-value standards, you can use Key-Value Sets.
If you want to store structured data, you should consider to use a SQLite Database.
You can also use the Internal Storage to keep files.
Since you want an approach more user-proof, I prefer the SQLite approach. Be aware that no method is 100% guaranteed, since rooted phones can grant access to physical data. At least, consider to encrypt sensitive data before sending to the database.
You also have the option of hosting a web service that is consumed by the app to gather information. It can be a lot safer, it is easier to be accessed by all instances of the application, but introduces internet dependecy.
Hope it helps.
The only good reference that I can find on the internet is this whitepaper, which explains what database tiering is, but not how it works:
The concept behind database tiering is
the seamless co-existence of multiple
(legacy and new) database technologies
to best solve a business problem.
But, how does it implemented? How does it work?
Any links regarding this would also be helpful. Thanks.
I think the idea of that document is you to put "cheap" databases in front of the "expensive" databases to reduce costs.
For example. Let's assume you have an "expensive" db...something like Oracle, or DB2 or even MSSQL (more realistically it's probably more of an issue with a legacy DB system that is not supported much or you need specialized resources to maintain). A database engine that costs a lot to purchase and maintain (arguably these are not expensive when you take all factors into consideration. But let's use them for the example).
Now if you suddenly get famous and your server starts to get overloaded what do you do? Do you buy a bigger server and migrate all your data to that new server? That could be incredibly expensive.
With the tiering solution you put several "cheap" databases in front of you "expensive" database to take the brunt of the work. So your web servers (or app servers) talk to a bunch of MySQL servers, for example, instead of directly to the your expensive server. Then these MySQL servers handle the majority of the calls. For example, they could handle all read-only calls completely on their own and only need to pass write-calls back to the main database server. These MySQL servers are then kept in sync via standard replication practices.
Using methods like this you could in theory scale out your expensive server to dozens, if not hundreds, of "cheap" database servers and handle a much higher load.
Database tiering is just a specific style of tiering. There are also application tiering and service tiering. It's a form of scalability.
What exactly are you asking? This question is rather vague.
This is a PDF from a course at Ohio State. What it discusses is a bit over my head, but hopefully you might understand it better.
Right now I'm developing the prototype of a web application that aggregates large number of text entries from a large number of users. This data must be frequently displayed back and often updated. At the moment I store the content inside a MySQL database and use NHibernate ORM layer to interact with the DB. I've got a table defined for users, roles, submissions, tags, notifications and etc. I like this solution because it works well and my code looks nice and sane, but I'm also worried about how MySQL will perform once the size of our database reaches a significant number. I feel that it may struggle performing join operations fast enough.
This has made me think about non-relational database system such as MongoDB, CouchDB, Cassandra or Hadoop. Unfortunately I have no experience with either. I've read some good reviews on MongoDB and it looks interesting. I'm happy to spend the time and learn if one turns out to be the way to go. I'd much appreciate any one offering points or issues to consider when going with none relational dbms?
The other answers here have focused mainly on the technical aspects, but I think there are important points to be made that focus on the startup company aspect of things:
Availabililty of talent. MySQL is very common and you will probably find it easier (and more importantly, cheaper) to find developers for it, compared to the more rarified database systems. This larger developer base will also mean more tutorials, a more active support community, etc.
Ease of development. Again, because MySQL is so common, you will find it is the db of choice for a great many systems / services. This common ground may make any external integration a little easier.
You are preparing for a situation that may never exist, and is manageable if it does. Very few businesses (nevermind startups) come close to MySQL's limits, and with all due respect (and I am just guessing here); the likelihood that your startup will ever hit the sort of data throughput to cripple a properly structured, well resourced MySQL db is almost zero.
Basically, don't spend your time ( == money) worrying about which db to use, as MySQL can handle a lot of data, is well proven and well supported.
Going back to the technical side of things... Something that will have a far greater impact on the speed of your app than choice of db, is how efficiently data can be cached. An effective cache can have dramatic effects on reducing db load and speeding up the general responsivness of an app. I would spend your time investigating caching solutions and making sure you are developing your app in such a way that it can make the best use of those solutions.
FYI, my caching solution of choice is memcached.
So far no one has mentioned PostgreSQL as alternative to MySQL on the relational side. Be aware that MySQL libs are pure GPL, not LGPL. That might force you to release your code if you link to them, although maybe someone with more legal experience could tell you better the implications. On the other side, linking to a MySQL library is not the same that just connecting to the server and issue commands, you can do that with closed source.
PostreSQL is usually the best free replacement of Oracle and the BSD license should be more business friendly.
Since you prefer a non relational database, consider that the transition will be more dramatic. If you ever need to customize your database, you should also consider the license type factor.
There are three things that really have a deep impact on which one is your best database choice and you do not mention:
The size of your data or if you need to store files within your database.
A huge number of reads and very few (even restricted) writes. In that case more than a database you need a directory such as LDAP
The importance of of data distribution and/or replication. Most relational databases can be more or less well replicated, but because of their concept/design do not handle data distribution as well... but will you handle as much data that does not fit into one server or have access rights that needs special separate/extra servers?
However most people will go for a non relational database just because they do not like learning SQL
What do you think is a significant amount of data? MySQL, and basically most relational database engines, can handle rather large amount of data, with proper indexes and sane database schema.
Why don't you try how MySQL behaves with bigger data amount in your setup? Make some scripts that generate realistic data to MySQL test database and and generate some load on the system and see if it is fast enough.
Only when it is not fast enough, first start considering optimizing the database and changing to different database engine.
Be careful with NHibernate, it is easy to make a solution that is nice and easy to code with, but has bad performance with large amount of data. For example whether to use lazy or eager fetching with associations should be carefully considered. I don't mean that you shouldn't use NHibernate, but make sure that you understand how NHibernate works, for example what "n + 1 selects" -problem means.
Measure, don't assume.
Relational databases and NoSQL databases can both scale enormously, if the application is written right in each case, and if the system it runs on is properly tuned.
So, if you have a use case for NoSQL, code to it. Or, if you're more comfortable with relational, code to that. Then, measure how well it performs and how it scales, and if it's OK, go with it, if not, analyse why.
Only once you understand your performance problem should you go searching for exotic technology, unless you're comfortable with that technology or want to try it for some other reason.
I'd suggest you try out each db and pick the one that makes it easiest to develop your application. Go to http://try.mongodb.org to try MongoDB with a simple tutorial. Don't worry as much about speed since at the beginning developer time is more valuable than the CPU time.
I know that many MongoDB users have been able to ditch their ORM and their caching layer. Mongo's data model is much closer to the objects you work with than relational tables, so you can usually just directly store your objects as-is, even if they contain lists of nested objects, such as a blog post with comments. Also, because mongo is fast enough for most sites as-is, you can avoid dealing the complexities of caching and generally deliver a more real-time site. For example, Wordnik.com reported 250,000 reads/sec and 100,000 inserts/sec with a 1.2TB / 5 billion object DB.
There are a few ways to connect to MongoDB from .Net, but I don't have enough experience with that platform to know which is best:
Norm: http://wiki.github.com/atheken/NoRM/
MongoDB-CSharp: http://github.com/samus/mongodb-csharp
Simple-MongoDB: http://code.google.com/p/simple-mongodb/
Disclaimer: I work for 10gen on MongoDB so I am a bit biased.
i am currently working on recommendation systems especially for audio files.but i am a beginner at this subject.i am trying to design database first with mysql but i cant decide how to do it.İt is basicly a system which users create profile then search for the music and system recommend them music similar to they liked.
which database should i use ?(Mysql
comes my mind as a first guess)
it is a web project and also then
with mobile side.Which technologies
should i use?(php,android
platform...)
what are the pitfalls of this
project.
how to design database for system
like that?
Any relational database should be good for storing the raw data like lists of songs, list of users, users' song preferences..
I think that you'll find that a relational databases (and SQL) are not that great for storing the various data structures that your recommender will be constructing. Your recommendation engine will probably creating data that doesn't really need to be in tables and manipulating it for storage in a relational database may just be wasted work.
Just be aware of what you are doing and don't spend time putting stuff into a SQL database if it feels wrong. Maybe look into using a document oriented database like MongoDB.
The recommender that I recently wrote is actually a Java server process that reads in the raw data from MySQL, does all of its work in-memory, and provides recommendation data to my application via an HTTP API. I didn't even bother storing the recommendation data permanently since it can be regenerated.
Go read "Programming Collective Intelligence". They have a number of fine algorithms for recommendations in Chapter 2, "Making Recommendations".
Well, this is a vague question and a half, but I'll do my best to answer:
MySQL is a solid database, and so is PostgreSQL. Both are free and open sourced. MySQL is more widely supported and a little easier to use, but Postgres has some very cool features and functionality that's worth taking a gander at. WikiVS has a good comparison of the two.
Smartphones are having better and better browsers. Use PHP or ASP.NET (whatever you're comfortable with), and then build out a mobile site which looks better on the smaller resolutions.
There are a lot. First and foremost, how good is your recommendation algorithm? Secondly, storing audio files can eat up storage space quickly. What's your plan for scaling? Thirdly, how well do you know database design? Can you design a large, hefty database and index it properly? If not, you need to start reading everything you can on indices and database design. Fourthly, it's a software project, and those always have pitfalls. The best you can do is post here when problems arise and we can always see what the fine people of StackOverflow can do to help.