sequelts VS kanel

You can use these template literal types + infer to build an entire SQL parser. I did a POC that infers SQL query types by parsing the SQL query on a type level:

https://github.com/nikeee/sequelts

However, building this parser is pretty cumbersome and supporting multiple SQL dialects would be lots of pain. While I'm not a fan of query builders per se, Kysely pretty much covers everything that my POC tried to cover (except that 0 runtime overhead). However, you get the option to use different DBMs in tests than in production (pg in prod, sqlite in tests), which is a huge benefit for a lot of people. sequelts was designed to work with sqlite only. And it's not a hack.

The only thing I can imagine where this would be useful is when you don't have control about what DB is being used, for example, when building a product that should be compatible with Postgres and MariaDB (and each is getting used). However, in the age of containerization, this isn't a big problem any more.

In some ORMs, I need to create types that the result of a query containing JOINs is mapped to. Others don't support them _at all_. In TypeORM, there is a query builder which forces you to put in _some_ SQL for things like "WHERE a in (b, c)".

I created a proof of concept of a different approach: Just embrace SQL and provide static typing based on the query. The return type of a query is whatever that thing is that the query returns in the context of the database schema. It's possible to do in TypeScript, by parsing the SQL query at development time:

https://github.com/nikeee/sequelts

One benefit is that it does not need any runtime code, as it's just a type layer over SQL. You don't have to rely on some type-metadata that TypeScript emits. That's why it also works with JavaScript only.

I don't like ORMs that use runtime types either. Most of the time, I want to write raw SQL.

So as an experiment, I created a library that statically types raw SQL:

https://github.com/nikeee/sequelts

The idea is to parse the SQL queries using TS's type system. The parsed query is combined with the database schema and therefore, we know what type the query will return.

This is especially useful due to TS's structural type system.

I'll just quickly plug Kanel (https://github.com/kristiandupont/kanel) which I use to generate Typescript types from a Postgres database. I agree with the author to think migrations-first, though I prefer to write them in SQL to ensure I can utilize all the powerful features that Postgres has to offer.

With it, I only get types for the tables and views etc., so any join will be untyped if done client-side. This is still a big win in my opinion, and I much prefer it to normal ORM's.

I made a tool that generates Typescript types out of a live Postgres database. I've had a request for Kysely support (https://github.com/kristiandupont/kanel/issues/273), but I more or less forgot about it. I would love to hear if that would be helpful.

There are tools that will generate typescript types from a database. I made one for Postgres. But it also works at "compile time", i.e. it doesn't look at a live database. I am not sure if that is what you are asking?

That's interesting. I use Knex a lot and I agree that it's very easy to end up just writing what is basically an ORM on the spot. I haven't quite decided if I think it's a real problem though.

I created and use Kanel (https://github.com/kristiandupont/kanel) to generate Typescript types from my Postgres database which helps a lot. Knex itself has some attempt at type safety but it gets confused quite quickly, so that's where it's tempting to override things.

Interesting. Someone asked me if I supported it in Kanel. At the time it was hard to extend Kanel and then I just forgot but perhaps I should take another look at it. I am not exactly overwhelmed with the types that Knex offers even though it does make an honest attempt.

I have so far found: - kanel https://github.com/kristiandupont/kanel - and pg-to-ts https://github.com/danvk/pg-to-ts

I’ve written before about the way I let the Postgres schema act as the source of truth by generating types with Kanel (assisted by Schemalint). In addition to this, I mention a homemade framework that sort of resembles a server-side Redux. This gives me typesafe database queries that are automatically reflected all the way to the frontend. I am frequently asked to make it open source and that is still the plan. I just need to untangle it from the Submotion source code which just never seems to be high enough priority. I promise I will get around to it :-)

We are using Kanel[1] for this right now — is there an advantage to using this instead?

[1]: https://github.com/kristiandupont/kanel

Sure. I've been using this lib https://github.com/kristiandupont/kanel to get types from my pg database and it makes it a breeze to use raw sql + ts.