Support computeBatchAtRuntime consuming SQL computed columns

[IlyaSemenov]

As a developer, I want computeBatchAtRuntime to be able to consume SQL computed fields. My particular use case is that I have a SQL computed field that calculates a certain figure with a SQL math expression, and then sometimes I also want this number converted through a currency exchange service (that needs async operations).

Disclaimer: I realise it might be impossible to achieve due to the typing loop, but I believe it could at least have some investigation.

Anyhow, this seems to work partially already, but not to full extent. The typings are not there and the query builder forgets to add the field alias:

class UserTable extends BaseTable {
  override readonly table = "user"

  override columns = this.setColumns(t => ({
    id: t.serial().primaryKey(),
    name: t.varchar(),
  }))

  computed = this.setComputed(q => ({
    upperName: sql`upper(name)`.type(t => t.varchar()),
    upperNameDoubled: q.computeBatchAtRuntime(
      // Type '"upperName"' is not assignable to type '"name" | "id"'.
      ["upperName"],
      users => users.map(u => u.upperName + "x2"),
    ),
  }))
}

await db.user.insert({ name: "Alice" })

await db.user.find(1).select("upperNameDoubled").then(console.log, console.error)
// (0.8ms) SELECT upper(name) FROM "user" WHERE "user"."id" = $1 LIMIT 1 [1]
// { upper: 'ALICE', upperNameDoubled: 'undefinedx2' }

[romeerez]

Here is my current draft:

class UserTable extends BaseTable {
  computed = setComputedV2((q) => ({

    one: sql`upper(name)`.type(t => t.varchar()),

    two() {
      return q.computeAtRuntime(this, ['one'], (record) => {
        return record.one + ' text'
      });
    },
  }));
}

It doesn't look great that you have to pass this, but it's the only way I could find, and it works - it is type safe.

[IlyaSemenov]

I see. It might be not worth pursuing in the end, this can always be implemented at application level. I just threw an idea that came to me while I was working on something.

[romeerez]

And I like the idea and I'd like to implement it. Not all the work has to be bug fixes :)

It's a cycle: add more bugs, fix some bugs, then it is balanced.

But I got you that it's not a priority for your case and can be postponed.

[romeerez]

I published the first step: you can reuse SQL computeds, documentation.

To be continued...

[mordechaim]

Thanks @romeerez , just a nitpick about the docs, you reference this.one and this.two instead of hello world.

[romeerez]

Nitpicks are welcome, I'll edit that