Exposed VS kotlinx.collections.immutable

So is it like Exposed for Kotlin which is a typesafe Kotlin DSL for building sql queries? I’ve been looking for something like this in typescript! https://github.com/JetBrains/Exposed

object TestDatabase { private val mySQLContainer: MySQLContainer = MySQLContainer("mysql:8.0.26").apply { withDatabaseName("test-db") withUsername("test-user") withPassword("test-password") start() // Start the container } init { val config = HikariConfig().apply { jdbcUrl = mySQLContainer.jdbcUrl username = mySQLContainer.username password = mySQLContainer.password driverClassName = "com.mysql.cj.jdbc.Driver" maximumPoolSize = 10 } val dataSource = HikariDataSource(config) // This doesn't connect to the database but provides a descriptor for future use // In the main app, we would do this on system start up // https://github.com/JetBrains/Exposed/wiki/Database-and-DataSource Database.connect(dataSource) // Create the schema transaction { SchemaUtils.create(Users) } } }

Exposed SQL is pretty good.

I am using Kotlins Exposed DSL to access my postgreSQL database. I am running an SQL query which involves doing a one-to-many left join, with the first table having tens of thousands of rows and the second table having millions of rows. The database is stored locally on the machine. I would expect the returned query to be less than one thousand rows.

I understand that `referrersOn` and `referencedOn` can be used, however in the documentations StarWars example, the child table needs to have a column indicating the parent_id row it is joined to. This does not work in my case as my child table can be associated to multiple parent_ids.

I am following this wiki to learn kotlin exposed. It contains an example of 'Referencing' using Star Wars data. I would like to create a scratch and/or console file in IntelliJ which reproduces this simple example. However When I try to run the code I get errors (see below). Is there something I am missing here?

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.

In Clojure, it is called an Atom. I created my own via AtomicReference and https://github.com/Kotlin/kotlinx.collections.immutable. It works really well in Kotlin. It works especially well if you use tons of coroutines.

So does Java! Also, kotlinx.collections is still not stable and I don't think they are intending to make it so any time soon.

If you want to have O(1) with prepend you use the LinkedList. You get a lot of functional benefits but also all of the downsides like no random access. You can use the https://github.com/Kotlin/kotlinx.collections.immutable library to get O(log_64(n)). I haven't spent a ton of time on Tries so I might be a little wrong on that bound. BTW, these are persistent immutable data structures. At work, we use them inside of AtomicReference to roll our own Clojure Atoms.

This is why Kotlin refers to List as read-only, and not immutable, and has created a library for truly immutable collections: https://github.com/Kotlin/kotlinx.collections.immutable

What I know is only based on this discussion. It seems that pcollections is really outdated and should not be considered.

If you want true immutable collections, kotlinx.collections.immutable provides them. They will likely be integrated into the language eventually with value classes and better immutability support.

I could see this argument made with Clojure, but I don't really see what makes Scala significantly better at FP than Kotlin. Kotlin has an official persistent data structures library nowadays, and it's got lambdas and higher order functions.

It's not immutable, it's read-only, https://kotlinlang.org/docs/reference/collections-overview.html . I think that's a false assumption. But I get the point - immutable collections are not part of the std - for very good reasons. But we know each other, I assume that you will disagree :) For people who know what they want and know all the implications, there is https://github.com/Kotlin/kotlinx.collections.immutable .