moja VS Slick

I want sum types.

I want a statically-typed way of constructing composable queries that follow SQL rather than reinvent a different thing. It doesn't have to be the same syntax but it has to be the same structuring.

I started writing one[0] and stopped before doing all the boilerplate code generation, having moved on from the JVM ecosystem for the time being. One thing it does is treat most things like sets so we don't end up with N+1 queries. Another trick it uses is collapsing constant expressions via an expression evaluation library[1].

[0] https://github.com/karmakaze/safeql

[1] https://github.com/karmakaze/moja

Over the years, I've written many apps and utilities for myself or others (that didn't end up get used). These are the interesting ones I remember. Many not quite complete/usable. Other than hackerer.news none of them are 'up' and running. Some have and others haven't been published as opensource.

- https://hackerer.news HN viewer (source[0]): I use daily so I can see today's top stories in reverse chronological order with mainstream topics sorted to the bottom.

- qwickly[1] keyboard layout: I use all the time as an easier to learn and more comfortable to type than Colemak/Tarmak

- safeql[2]: Java type-safe SQL expression composer that reduces constant expressions and eliminates N+1 queries loading associations by always operating on set relation or array of models.

- moja[3]: Composable computation pipelines for Java: Async, Lazy, Option, Try, Result, Multi (List), Stated, Reader, Logger, Writer.

- gitgrep.com[4] Opensource SaaS version of etsy/houndd (now called hound-search).

- statuspages.me: Status page aggregator with dynamic javascript for scraping each source using selector expressions.

- movies to watch aggregator: with links to sources to watch. It was hard then to get 3rd party deep links into streaming sites so included some torrent links. Got a DMCA phone call, so took it down. Combined thumbnails, summaries, actors(?), imdb ratings, links.

- java2cpp: Translate a moderately sized java app with test suite to c++, not 100% required final manual fixups.

- swift2java (or maybe it was java2swift, it's fuzzy now): translate Swift to Java obviously, using ANTLR4. Not 100% required final manual fixups.

- gui2log: to make an ASCII rendition of on-screen GUI widgets into an application log file when form submitted, so users couldn't complain that they saw X, but got Y.

- some basic stats/ML algorithms: k-nearest neighbour, RNN back-propagation, etc?

- Java in-memory DB: Small SQL-like memory tables with indexing/searching.

- wwwsqldesigner: This exists as opensource and I extended it to infer foreign key relationships based on naming conventions used in a MySQL schema. It was great for zooming around a large ERD.

- tracelog: combination of microservices parent/child span logging and generated high level events shown as a sequence diagram. Integrated with Loggly for full/verbose logs of selected high-level events.

- pcl2bmp downscaler: Reduce high resolution HP LaserJet (PCL5) printed to file to lower resolution bitmap pages for screen display (before retina DPI was common). It aimed to shrink same-color areas and preserve black/white transitions while reducing.

[0] https://gitlab.com/karmakaze/hackerer-news

[1] https://github.com/qwickly-org/Qwickly

[2] https://github.com/karmakaze/safeql

[3] https://github.com/karmakaze/moja

[4] https://github.com/gitgrep-com/gitgrep

Sure, SafeQL[0] SQL library. It's been sitting in a close but not enough to promote state for a while. The main thing I wanted was to have generation of the bindings to existing DB schema. I also want to combine using Moja[1] datatypes for uniform handling of single/multi, normal/async, and errors.

[0] https://github.com/karmakaze/safeql

[1] https://github.com/karmakaze/moja

I made a similar thing for Java moja Options as needed other projects. It sort-of works but it's not great.

Made a PR on slick to document this https://github.com/slick/slick/pull/2760 (workaround is quite easy, you can just define def tupled = (apply _).tupled in the companion object of the case class and it will also compile for all Scala versions).

The Scala ecosystem has a few ways to do composable type-safe query building, e.g. Slick[0] or more recently Quill[1]. . I believe both also have ways to do compile-time string interpolation (e.g. sql"""select * from users where id = ${user.id}""") which generate prepared statements (I know Slick does prepared statements. Quill has similar macros but I haven't looked into how safe they are to use).

[0] https://scala-slick.org/

Release notes at https://github.com/slick/slick/releases/tag/v3.5.0-M3

With all this in mind, I landed at the first candidate: slick from https://scala-slick.org/ that you all probably know.

I think Slick's current priority is also getting in Scala 3 support: https://github.com/slick/slick/issues/2177

Future releases might not be announced here. To get notified, go to https://github.com/slick/slick, click the Watch dropdown button at the top, select Custom, check Releases, and click Apply.

https://github.com/slick/slick/pull/2097 now I use slightly lower version of slick so this might be an upgrade that resolves (I do recall using it in 21 and it was still buggy and I filed a ticket, which I cannot find at the moment), but given a complex enough query (we have one in PROD which has tons of flexibility in terms of filters that can be passed in) but it also makes for complex code.

I started writing a reply but then I realized it would be long and depends on exactly what you mean, so maybe it's better to post the question in https://github.com/slick/slick/discussions/categories/questions?

I purchased the very entertaining book Seven Languages in Seven Weeks. Although I found Haskell fascinating and tempting, I knew it was unrealistic to introduce it in our company. Scala on the other hand looked like it could be the holy grail: All the characteristics I was looking for, no need to abandon the JVM and its cornucopia of tools and libraries, and the possibility for coexistence with Java and therefore incremental adoption. After implementing some simple programs to identify any immediate risks of committing to the language and its ecosystem, I started to introduce Scala in customer projects. Luckily, I was fortunate enough to work with open-minded, curious, and ambitious team members who were also experienced enough to appreciate the benefits of the language. We immediately applied our experience with functional programming, and embraced immutability. Libraries like Slick and Akka HTTP (we actually started out with its predecessor, Spray) made building database-backed REST services a breeze. And the resulting code was robust and highly maintainable. Scala's expressive type system and type inference made it easy to build a restrictive, consistent domain model without bloating the code. There was virtually no overhead. Any boilerplate could be easily abstracted out. In the end, the application code felt natural, concise and elegant. Programming was fun again.