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Datomic, from Ruby, from Rails

Yoko Harada • June 25, 2013 • Portland, OR

In the video titled "Datomic, from Ruby, from Rails" presented by Yoko Harada at Rails Conf 2013, the focus is on using Datomic, a NewSQL database developed by Rich Hickey, with Ruby applications, particularly in a Rails environment through the Diametric gem.

Key Points Discussed:
- Introduction to the Speaker and Context: Yoko Harada, a JRuby core contributor and developer at Relevance, introduces himself and the topic of his session, set against the backdrop of the final day of the conference.
- Overview of Diametric Gem: The session provides an introduction to the Diametric gem, an ActiveModel compliant wrapper for Datomic. It supports interactions with Datomic using either REST or peer services and emphasizes the open-source nature of the gem, encouraging contributions.
- Understanding Datomic: Harada explains Datomic’s unique properties - primarily its immutability, schema-less nature, and time-based database capabilities, contrasting it against traditional relational databases (RDBMS). He points out that, unlike RDBMS, Datomic allows for the preservation of all historical data (facts), which are immutable.
- Diatomic and Ruby Integration: Harada elaborates on how the Diametric gem allows Rubyists to utilize Datomic effectively, including the challenges faced in crafting a Ruby-like API that still communicates Datomic's core principles. He showcases how models can be defined and how data can be manipulated without needing to stress about the underlying schema definitions typical in RDBMS.
- Demo: The presentation includes a live demonstration showcasing the creation of models, data transactions, and querying data using the Diametric API. This practical illustration helps solidify understanding by showing real-time interactions with the Datomic database using Ruby code.
- Future Improvements: Harada concludes by noting that while the integration works, there are still areas for enhancement, particularly in function mapping and API support, and he invites contributors to improve the existing framework.

Conclusion: The session emphasizes that integrating Datomic with Ruby and Rails is achievable and can leverage the new capabilities brought forth by modern database design principles. Harada encourages Ruby developers to explore Datomic through the Diametric gem, highlighting its potential to enhance Ruby on Rails applications while acknowledging the current limitations in the API.

Datomic, from Ruby, from Rails
Yoko Harada • June 25, 2013 • Portland, OR

Datomic is a new database categorized as NewSQL and was created by Rich Hickey. Everybody knows this big name and thinks of Clojure. It is true Datomic fits well to Clojure programming. However, it is not only for Clojure people.
Absolutely, Rubyists can use it. We have Diametric gem (https://github.com/relevance/diametric). Using Diametric, we can dive into Datomic from Ruby, from Rails.
On Diametric, Datomic's entity is an ActiveModel compliant. Diametric supports Rails' scaffolding. Its usage might look like Datamapper or MongoDB. Eventually, Diametric's API design settled in a bit far from Ruby, Rails style. In another word, it is not ORM-like. Even though the API design may puzzle Rubyists, Diametric chose the one to expose Datomic's intrinsic properties. It is to leverage a good side of Datomic for us. I believe the more Rubyists use Diametric, the more they like it.
In my talk, I'll introduce Diametric gem and how to use it as well as why its API design is good for us. Also, I will cover how Ruby helped to integrate Datomic API in Diametric gem.

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RailsConf 2013

00:00:16.320 Okay, so hello everyone. Good morning.
00:00:22.080 Thank you for coming to my session on the last day in the morning; I really appreciate it.
00:00:28.480 Today, I'm going to talk about Datomic from Ruby on Rails. It's a straightforward title, and I'm excited to share my insights.
00:00:36.320 My name is Yoko Harada, and you can find me on GitHub and Twitter under the username 'yokuharada'.
00:00:44.800 I'm a JRuby core contributor and a JRuby enthusiast, which is quite important to remember.
00:00:52.160 I'm also a contributor to the NoCalgary project, and I work for Pure Java at NoCalgary.
00:01:03.680 As a Japanese person, I find some words a bit difficult to pronounce, including 'relevance'.
00:01:10.720 Currently, I work for Relevance as a developer. Today, I will cover three main topics.
00:01:28.560 First, I will introduce the Diametric gem. Then, I'll provide an overview of Datomic for those who are unfamiliar with it.
00:01:34.640 Finally, I'll delve into the details of how the Diametric gem works.
00:01:40.720 To start, the Diametric gem is an ActiveModel wrapper for Datomic.
00:01:46.399 Using this gem, developers can interact with Datomic in a way that's familiar to Rubyists.
00:01:53.520 For those who do not know, Datomic is a database that leverages immutable data.
00:02:00.159 It's built on a different paradigm than traditional relational databases.
00:02:05.360 The first thing I need to clarify is that the Diametric gem is hosted by Relevance.
00:02:10.000 However, it is an open-source project, allowing anyone to contribute. I appreciate any pull requests from the community.
00:02:26.080 Relevance sells Datomic licenses and provides consulting, but the gem itself is a third-party product.
00:02:33.599 Now, I'd like to discuss something called coding time.
00:02:40.800 Our employees are encouraged to work on projects of their choice during what we call '20% time,' which occurs every Friday.
00:02:55.440 During last year's JRubyConf, I worked on a picture project as part of this initiative.
00:03:09.760 Three developers have significantly contributed to the Diametric gem.
00:03:15.120 Quentin introduced the project, followed by Ryan, and I joined later.
00:03:22.320 At present, I am the only one actively contributing to the gem.
00:03:27.440 The Diametric gem presents certain challenges. I will show examples of how Datomic functions later.
00:03:35.280 When people mention Datomic, it often comes with the association of Clojure, which is the language primarily used with it.
00:03:48.480 Many developers prefer to use Datomic with Clojure, but there is also a Java API available that can be accessed via REST services.
00:03:55.680 For Rubyists, we will need to make some adjustments, which I will discuss further.
00:04:05.440 Now, let's talk about Datomic itself.
00:04:10.800 Datomic was created by Rich Hickey, the well-known creator of Clojure.
00:04:27.040 There are often questions about whether Rich Hickey works for Relevance; the answer is no.
00:04:32.479 Datomic is a joint venture between Rich and Relevance, and they collaborate on its development.
00:04:44.000 Now, let's discuss the definitions related to Datomic and its categorization.
00:04:57.679 It is classified as a NewSQL database, but naming conventions can be confusing.
00:05:08.160 Datomic guarantees ACID properties akin to those found in traditional RDBMS.
00:05:14.720 Rich Hickey designed Datomic with simplicity in mind, ensuring minimal schema and data structures.
00:05:21.359 In Datomic, the schema is represented as simple arrays and hashes.
00:05:36.640 Here's an example: don't worry too much about the schema itself.
00:05:44.800 Clojure developers can define the schema, but the Diametric gem generates an appropriate schema for Ruby.
00:05:58.480 A few key features distinguish Datomic from traditional RDBMS.
00:06:12.680 First, in Datomic, data is treated as immutable.
00:06:27.679 This architecture allows for reasoning over time effectively.
00:06:39.039 For instance, if we have a table with a boyfriend's picture, when a new picture is added, the old one is not deleted; instead, a fact is created.
00:06:54.480 This approach removes the need for data deletion, as Datomic implements this with a focus on immutability.
00:07:11.760 Rich Hickey called this approach 'fact-oriented programming,' wherein facts are never altered.
00:07:26.880 A good example of this is how GitHub IDs remain as facts that can be traversed over time.
00:07:39.120 The ability to roll back to previous states is a significant advantage in Datomic.
00:07:47.360 Let's consider a database state rollback example, representing a point in time.
00:07:55.680 In essence, we can visualize this feature as an OS X time machine.
00:08:07.920 On the programming side, Datomic has a Closure and Java API, along with its query engine.
00:08:24.719 This structure makes Datomic highly scalable because we can control operations from the programming level.
00:08:37.360 To summarize, Datomic distinguishes itself from traditional RDBMS through its handling of facts and immutability.
00:08:51.760 Let's shift our focus back to the Diametric gem.
00:09:02.880 The gem simplifies how we interact with Datomic, as we do not need to manually handle the schema.
00:09:12.560 In the gem, we define classes that include the Diametric entity, and it manages the schema for us.
00:09:20.320 Thus, integrating peer services into our Ruby applications is straightforward.
00:09:28.640 Using the API, we can set attributes and interact with the data seamlessly.
00:09:42.480 The Diametric gem generates dynamic transaction data to simplify data operations.
00:09:56.560 When we create a new model instance and save it, all the transactions are managed effectively.
00:10:06.720 In the case of updating or deleting records, the gem handles this with the concept of transactions as well.
00:10:18.560 Next, I’ll provide a brief demonstration of working with the Diametric gem.
00:10:30.480 First, I’ll connect to Datomic and create a schema.
00:10:41.680 The Diametric gem generates the required schema for our application, allowing us to proceed without complications.
00:10:56.240 The ability to specify connections and define attributes is incredibly useful.
00:11:11.360 When querying, we can leverage the gem to simplify interaction with the data.
00:11:26.720 For instance, the gem provides an easy way to filter results based on specific attributes.
00:11:44.560 Furthermore, the framework supports complex queries, making it manageable to retrieve relevant entries.
00:12:01.680 Let's talk about a more complicated example involving neighborhoods.
00:12:16.640 In this instance, the challenge is navigating relationships between different data models.
00:12:29.440 For example, I’m looking to identify neighborhoods based on certain characteristics, which can be straightforward with the right queries.
00:12:45.440 The data structure allows for easy traversal up and down the relationships.
00:12:56.480 This flexibility is one of the strengths of using Datomic with the Diametric gem.
00:13:08.160 As such, querying for complex nested data or relationships becomes feasible.
00:13:24.320 The capability to read all current data states, even with large datasets, further emphasizes Datomic's efficiency.
00:13:37.360 We often deal with many results, and this performance is crucial for applications that rely on rapid data access.
00:13:55.920 By defining schemas carefully, we can ensure seamless integration into Ruby applications.
00:14:06.799 Returning to the original context, let’s consider the practical implementation of Datomic from Rails.
00:14:23.880 This setup allows Ruby developers to interact with Datomic as they would with standard database systems.
00:14:36.240 I have a working example of integrating Datomic, showcasing its functionality with Rails.
00:14:53.200 In this project, I utilized jRuby on Rails and the Diametric gem.
00:14:59.360 This integration serves as a valuable demonstration of how these technologies can cooperate.
00:15:06.000 The outcome is a functional Rails application leveraging the strengths of Datomic.
00:15:17.680 To conclude, while there are some challenges with mapping functions, the overall experience has been rewarding.
00:15:31.840 I encourage contributions from the community to improve the gem further.
00:15:53.680 Thank you all for attending this session, and I hope you can explore the possibilities that Datomic and the Diametric gem offer Ruby developers.
00:16:15.680 If you have any questions or need clarification on anything discussed, feel free to ask.
Yoko Harada
@yokolet
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