Exposed VS MapDB

Exposed by JetBrains https://github.com/JetBrains/Exposed

Alternatively there are... hybrid solutions like Kotlin's https://github.com/JetBrains/Exposed or https://jdbi.org/ that don't quite... do all the heavy lifting for querying but allow you to sorta stitch queries together manually.

In our last episode (https://youtu.be/Uza\_dWsNMUs) we worked out how to save stock items in PostgreSQL (https://www.postgresql.org/) using the JetBrains Exposed library (https://github.com/JetBrains/Exposed). This time we refactor our existing file-based storage, extracting an interface that we can implement with files, in-memory, or with Exposed. For the database version, instead of replacing items in a table when they change, we choose to implement an append-only datastore. This keeps all the old versions of every row, using a query to select the latest versions when we want to see the current state. This has the advantage that we can rebuild the state of our system if things go wrong, and may also be faster than amending when we consider transactions. This is part 62 of an exploration of where a Test Driven Development implementation of the Gilded Rose stock control system might take us in Kotlin. You can see the whole series as a playlist https://www.youtube.com/playlist?list=PL1ssMPpyqociJNwykAOB9\_KEZVW7BW7m2 and the code on GitHub https://github.com/dmcg/gilded-rose-tdd If you like this, you’ll probably like my book Java to Kotlin, A Refactoring Guidebook (http://java-to-kotlin.dev). It's about far more than just the syntax differences between the languages - it shows how to upgrade your thinking to a more functional style. I have some free time between producing videos and working for team Gilded Rose. If you like these videos I'd like to work with you - please get in touch - [email protected]

I have used hikari and exposed to do this in the past with postgres, although other dialects are supported.

This falls apart as soon as you need to chain transactions across multiple services/DAOs. You end up making everything non-suspend or use suspendTransaction and have to pass the parent txn around which isn’t ideal (https://github.com/JetBrains/Exposed/issues/1477)

Whether or not we persue our Event Sourcing experiment from the lastepisode, we know that we want to store our stock data in a database ofsome sort. So today we investigate using the JetBrains Exposed library (https://github.com/JetBrains/Exposed) to write to and read from PostgreSQL (https://www.postgresql.org/).

I used exposed to access a database https://github.com/JetBrains/Exposed. You can use sqlite for the easiest setup.

And sorry to rain on your parade but; keep in mind that something similar already exists: Exposed. And it's rather unlikely someone would use yours over something like what you made that has no OS license, no community and no tests.

Anyway, without further ado, I found MapDB (https://github.com/jankotek/mapdb) which does exactly that. Of course, they also provide their own Java collection implementations as well, so I suspect using it with Vavr would be a poor idea, but it is very cool in its own right anyway. Of course, there is also Apache Derby and HSQLDB, and those great options with a long history as well. I haven't played with these in a while though, so I might give them a try again soon for some personal stuff.

In Java I like

https://mapdb.org/

It is more feature rich than you want but in Python I'd probably just use sqlite3 since it is in the standard library.

I have had good results with mapdb