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NoSQL

DynamoDB Scan: the most efficient operation

By Franck Pachot

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The title is provocative on purpose because you can read in many places that you should avoid scans, and that Scan operations are less efficient than other operations in DynamoDB. I think that there is a risk, reading those message without understanding what is behind, that people will actually avoid Scans and replace them by something that is even worse. If you want to compare the efficiency of an operation, you must compare it when doing the same thing, or it is an Apple vs. Orange comparison. Here I’ll compare with two extreme use cases: the need to get all items, and the need to get one item only. And then I’ll explain further what is behind the “avoid scans” idea.

I have created a table with 5000 items:

NoSQL and SQL: key-value access always scale

By Franck Pachot

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I have written about some NoSQL myths in previous posts ( and here) and I got some feedback from people mentioning that the test case was on relatively small data. This is true. In order to understand how it works, we need to explain and trace the execution, and that is easier on a small test case. Once the algorithm is understood it is easy to infer how it scales. Then, if readers want to test it on huge data, they can. This may require lot of cloud credits, and I usually don’t feel the need to do this test for a blog post, especially when I include all the code to reproduce it on a larger scale.

Amazon DynamoDB: a r(el)ational Glossary

By Franck Pachot

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There are many NoSQL databases. And, because SQL is an ISO standard, “No SQL” also means “No Standard”. Many have a similar API and similar objects, but with completely different names. Today, NoSQL databases are used as an additional datastore for some well-defined use cases for which a hashed key-value store fits better than a relational table. And it quickly became “Not Only SQL” as it is complementary to RDBMS databases using SQL. But at the origin, the idea was to replace the RDBMS databases, refusing the SQL API, and then inventing a “No SQL” data store. When you want to replace something rather than proposing something new, you often adopt the same language to make it look similar. And this why, in my opinion we find some relational database terms like “Table” and “Index”. But they have a different meaning. Here is a dictionary where I try to explain the DynamoDB artifacts and differentiate from their Relational and SQL meaning.

Amazon DynamoDB: the cost of indexes

By Franck Pachot

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That’s common to any data structure, whether it is RDBMS or NoSQL, indexes are good to accelerate reads but slow the writes. This post explains the consequences of adding indexes in DynamoDB.

RDBMS (vs. NoSQL) scales the algorithm before the hardware

By Franck Pachot

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In The myth of NoSQL (vs. RDBMS) “joins dont scale” I explained that joins actually scale very well with an O(logN) on the input tables size, thanks to B*Tree index access, and can even be bounded by hash partitioning with local index, like in DynamoDB single-table design. Jonathan Lewis added a comment that, given the name of the tables (USERS and ORDERS). we should expect an increasing number of rows returned by the join.

In this post I’ll focus on this: how does it scale when index lookup has to read more and more rows. I’ll still use DynamoDB for the NoSQL example, and this time I’ll do the same in Oracle for the RDBMS example.

A lesson from NoSQL (vs. RDBMS): listen to your users

By Franck Pachot

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I have written a few blog posts about some NoSQL (vs. RDBMS) myths (“joins dont scale”, “agility: adding attributes” and “simpler API to bound resources”). And I’ll continue on other points that are claimed by some NoSQL vendors and are, in my opinion, misleading by lack of knowledge and facts about RDBMS databases. But here I’m sharing an opposite opinion: SQL being user-friendly is now a myth.

DBPod – le podcast Bases de Données

By Franck Pachot

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J’essaie quelque chose de nouveau. Je publie beaucoup en anglais (blog, articles, présentations) mais cette fois quelque chose de 100% francophone. En sortant du confinement, on reprend les transports (train, voiture,…) et c’est l’occasion de se détendre en musique mais aussi de s’informer avec des podcasts. J’ai l’impression que c’est un format qui a de l’avenir: moins contraignant que regarder une video ou ou lire un article ou une newsletter. Alors je teste une plateforme 100% gratuite: Anchor (c’est un peu le ‘Medium’ du Podcast).