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Closed 11 years ago.
We have requirements that force us to have two layers of databases. A good caching solution backed by large distributed database. We are thinking to use redis for fast read and write. We are not yet settled for the database at backend, however we would prefer it to have following properties:
consistent over time.
robust (no data loss).
reasonably fast read.
distributed.
We are exploring cassandra and Mongodb as our options. Hbase might be a option too. Kindly let us know your views/ current state of work. We are expecting some comparative analysis which could be like in http://kkovacs.eu/cassandra-vs-mongodb-vs-couchdb-vs-redis , but should be more upto date and can give us better insight. An example usecase could be like when someone post a comment in facebook. The comment is then visible to all its friends in real time.
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Closed 9 years ago.
I am a Mongo newbie and wanted to know if there are any tools that will help me test MongoDB? Especially, if they help me automate testing of the tables (or collections) in MongoDB. I did a few internet searches but got very confused. Any help will be appreciated.
Thanks!
Two clients I found useful when testing/looking at data within the db are:
MongoVue - It's free and allows you to see up to 3 documents at a time; and has multiple ways of displaying the data (text form, table form, etc.) Quite nifty, but the cool features expire after 14 days, then you have to pay.
MongoExplorer - It's a little less friendly looking thatn MongoVue, but it is very simple to use, and it is absolutely free. It has some more advanced options as well - such as the ability to see GridFS data (this is a paid feature in MongoVue).
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Closed 10 years ago.
My question seems to be dump, but because i was studying this new technique, i've found that NoSql has changed from its beginning, for example, in the beginning there was the problem of see your own update, and for example Facebook dident let users to update their comments due to the write once, read many
So, do i change all concepts that i've read in 2010-2012 tutorials?
Has NoSql beat the CAP theorem ?
I agree this can easily turn into discussion. I'll give brief answers from my experience to your two questions:
No, the concepts haven't changed. The landscape seems to be growing quite a bit as lots of companies get into the NoSQL space. Beware vendor promises!
No way. Just read this article this morning, it is a great explanation on some of the issues with the CAP theorem: http://codahale.com/you-cant-sacrifice-partition-tolerance/
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Closed 10 years ago.
Where ever I read I see experts writing to stay away from typed datasets and use the entity framework or similar.
On the other hand almost every ado.net book I read will show first how to use datasets and some of them only use datasets, that gives me the impression that its not bad. if it is why teach it for the new programers?
All depends on what you want to do with the data you're pulling from your DB.
I use a DataSet to load data in to a Crystal Report because it plays well together. Anywhere else in my app i use mostly anonymous types. Either way i use the EntityFramework to pull the data from my DB. I get results much faster that way than using ADO.NET and DataSets. If i need raw performance I use ADO.NET. For batch updates for example.
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Closed 10 years ago.
As per the article at W3Techs, Perl ranks the lowest among the server side scripting languages, even less than Java? Is there any reason behind it? Perl, as far as I see, is very popular, and an awesome language, how come it is hardly used by websites? Does it have issues with server side scripting?
This article has a lot of details on how W3Techs gets their data: http://w3techs.com/blog/entry/usage_of_perl_for_websites_fell_below_1_percent
As i did some analysis on this, let me summarize in short that the data presented by W3Techs is deeply flawed and extremely misleading. First off, it is important to know that they detect technologies of sites by running simple scripts at them that look for file suffixes in urls and then just take that and never verify with the site owner. As such they have a "no-detect" rate of 17.6% (plus an unknown "false-detect" rate). A more correct version of their chart would be this:
If you'd like to get more details and more mistakes in their data methodology, please take a look at the comments of the article, especially those written by "Mithaldu" or "Christian Walde", i.e. me. I posted extensively there as to why their data is nearly useless and why they're even misinterpreting the data they do have.
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Closed 9 years ago.
Are there significant performance issues when using nested(2 level deep at max) queries in PostgreSQL?
I use version 8.4.2
I am asking because I am planning to use quite a lot of those soon on a busy website..
The boring answer: it depends on the query and your data.
To write (and read and understand) a nested query might be easier than writing a non-nested one, but you might end up paying the price in reduced performance. During my previous database project we ended up rewriting quite a few of the more critical queries to avoid nesting and we saw order of magnitude performance improvements.
EXPLAIN is your friend. You should learn to love it and how to use it :)
http://www.postgresql.org/docs/current/static/sql-explain.html
Not really.
If you want to improve, does not forget to runs analyze on all tables periodically.
Your question is waaaaaaaaaaaaaaaaaaaaaaay too general. There isn't any inherent issue with using "nested" queries in Postgres, no matter how many levels deep. You need to post specific queries if you have issues.
Additionally...if you're designing a new system, then why 8.4 and not 9.0? And even on 8.4, you should update to 8.4.5.