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Apache Airflow Big Data algorithms Big Data problems - solutions Data engineering patterns General Big Data General data engineering Graphs SQL
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I have already described grouping sets feature in the context of Apache Spark. But natively they are a part of SQL standard and that's why I would like to extend the previous post here. After all, you don't need Big Data to use them - even though nowadays it's difficult to not to deal with it.
Last time we've discovered the INTERSECT operator. To recall it quickly, it returns all rows that are defined in the combined datasets. Today we'll discover another operator, doing the opposite and called depending on the vendor: MINUS or EXCEPT.
Key-value stores have the advantage of being a kind of distributed and high-available memory cache. But even though they're quite easy to manipulate thanks to the key-based access, they also have some complicated tasks. One of them is the strategy of picking a good key.
Some time ago I wrote a post about the graph data processing with streams. That article was based on X-Stream framework proposed by the searchers of EPFL research institute. At this occasion, I also mentioned the existence of newer alternative for X-Stream, adapted for distributed workloads, called Chaos. I voluntary omitted the explanation of Chaos in the previous post. Putting it aside of X-Stream would introduce too many new concepts. But now, after some weeks of graph processing discoveries, I would like to return to the successor of X-Stream and present it more in details.
Thanks to modern Big Data solutions like BigQuery or Apache Spark SQL, the knowledge of the advanced SQL concepts is important. After covering the operations like window functions or grouping sets, it's time to show another interesting SQL feature, the INTERSECT operator.
The series about graph processing continues. Today it's the moment to analyze some major graph processing frameworks and choose the framework that I'll present more in details in incoming posts.
Big Data enforces denormalized storage. Joins are costly and it's often much more efficient to store all related information in a single row. Such rows with a lot of columns are called wide rows and they'll be explained in the sections below.
Because of its connected nature, graph structure has its own branch in data mining. Thanks to this branch we can get insight into relationships and dependencies between vertices.
As told many times in previous posts, one of the most challenging tasks in distributed graph processing is the partitioning. Connected nature of the graph components makes the partitioning hard. Hopefully, the researchers continue to propose the solutions.
Until now we've discovered exclusively the concepts devoted to computing distributed graphs. But the compute part can't go without storage. And since for the latter in the context of graph we can't talk about the storage, it requires its own detailed explanation.
During last weeks we've discovered a lot about graph data processing in distributed world. However we haven't learned yet about the problems the graphs can solve. And it's as important as the knowledge about the processing techniques. Hopefully, this post will try to catch up this late.
Previously described vertex-centric model is not the single one used to process graph data. Another one uses subgraphs as the processing unit.
Use cases of streaming surprise me more and more. In my recent research about graph processing in Big Data era I found a paper presenting the graph framework working on vertices and edges directly from a stream. In case you've missed that paper I'll try to present this idea to you.
Graph data processing, even though seems to be less popular than streaming or files processing, is an important member of data-oriented systems. And as its "colleagues", it also has some different processing logics. The first described in this blog is called vertex-centric.
In this blog I've covered the topics about relational databases, key-value stores, search engines or log systems. There are still some storage systems deserving some learning effort and one of them are graphs considered here in the context of data processing.
Distributed computing opened a lot of possibilities and horizontal scaling is only one of them. But at the same time it brought some new problems that we need to address during applications conception. And writing a data on different data stores inside one transaction is the one of them.
A lot of names in IT come from the real world phenomena. One of them are epidemic protocols, aka gossip protocols, covered in this post.
Having data close to the computation has a lot of advantages. This idea called data locality is not new since it was popularized with Hadoop MapReduce. Despite of that, it's worth recalling some of its main points and trying to adapt it to modern data pipelines most of the time based on cloud services.
Some time ago I've started the series of posts about immutability in data-oriented applications. One of approaches helping to deal with it was based on version flags. But fortunately it's not the only solution - especially for the ones who don't like to mix valid and invalid data in a single place.
Querying big amounts of data has never been so simple as nowadays. Amazon Redshift and Azure SQL Data Warehouse are one of the solutions. But using them wouldn't be possible without a more global concept known as MPP.
