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How does a relational database work?

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Re: How does a relational database work?

#26

Post by threeseed »

mgachka wrote: post #6
mgrennan wrote: post #4

Not that Cassandra and Hadoop don't have a place. But because NO-SQL is hot I see lots of young coders (I'm and old DBA) try to turn document store systems into relational databases. They should all be made to read this post.

(I'm the author of the article) I'm 28 and I’m currently a Big Data developer (I use Hadoop, HBase, Hive …) and I don’t understand the buzz surrounding Big Data and NoSQL. With a relational database the complexity is hidden (more or less…) whereas with Big Data and NoSQL the developer needs to deal with this complexity himself/herself. As a result, most of the Big Data applications I’ve seen don’t work well. A really…

Not really sure what you are talking about.

Teradata, Oracle, PostgreSQL for example are reasonably complex databases to cluster and manage yourself. Just as easy/hard as setting up HDFS and installing Hive. In all cases people who are at big data scale are buying OTS solutions e.g. Cloudera appliance. They aren't rolling their own.

And if you are using Hive then I can understand why you are not feeling the buzz. But play around for Spark for a while and it's easy to see the future. Being able to write Scala/Python/SQL/R against a data set that can be anywhere from 100MB to 100PB without any changes is pretty compelling.

Re: How does a relational database work?

#27

Post by faragon »

Be careful with theoretical asymptotic complexity (big O) related to execution time. E.g. if your algorithm time complexity is O(1), but internally calls a higher complexity function, e.g. malloc(), implemented with higher complexity, e.g. O(log n), your algorithm time complexity would be O(log n) and not O(1). It could be even worse: on average or typical constant time algorithm could be in reality an O(n) one: e.g. case of hash table reindexation (that's the reason of why many big data structures, including most SQL databases, requiring real time behavior, are implemented as trees, tree hierarchies/division/clustering, instead of big hash tables).

Re: How does a relational database work?

#29

Post by michaelmior »

Cakez0r wrote: post #25

> Nowadays, many developers don’t care about time complexity … and they’re right! That's a pretty bold statement... Very thorough explanations though!

I think the important thing is knowing when not to care. Unfortunately, a lot of developers don't care because time complexity isn't even on their radar. So in the times when it does matter, they get burned.

Re: How does a relational database work?

#30

Post by rhizome »

mkehrt wrote: post #11
jchrisa wrote: post #8

Earlier quoted context omitted.

At Couchbase we did a survey of developers (this was ages ago) and the biggest motivator for NoSQL was schema flexibility. Not having to coordinate migrations is seen as a productivity boost. [1] The other thing document databases can offer that relational databases struggle with is taking subsets (which we use for offline sync.) [2] [1] http://blog.couchbase.com/nosql-adoption-survey-surprises [2] http://developer.c…

As someone who spent several years studying programming languages, the thing that drives me crazy about traditional relational databases is the assumption that all data is tuple-structured. Much data is structured as unions of alternates or more complex things like maps. Shoehorning your data model into a tuple-based system is always possible, but often unnatural. The place NoSQL shines is the acknowledgement that mo…

Where do you get that "most data is complex" in a way that leans away from relational DBs?
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