Referentially transparent API

[steida]

An expression is called referentially transparent if it can be replaced with its corresponding value (and vice-versa) without changing the program's behavior.

It would simplify Kysely usage and unlock further optimizations. And it's little change I believe.
Take a look how I'm using Kysely in React:

const { data, refresh } = useThingsDB(
  useCallback((db) => db.selectFrom('thing').selectAll().execute(), []),
);

useThingsDB is React Hook (composed from other hooks but that's irrelevant now), which takes Kysely query as a parameter. Note useCallback usage. It makes callback stable because it must be stable.

What am I proposing is toString overload that would serialize Kysely toString and fromString that would deserialize it. With such API, it would be easy to cache etc. Kysely queries.

const { data, refresh } = useThingsDB((db) =>
  db.selectFrom('thing').selectAll(),
);

What do you think?

[koskimas]

So you want to be able to serialize queries, not the whole Kysely instance with drivers, connections, plugins and all?

So something like this:

const serialized: string = db.selectFrom('thing').selectAll().serialize()
const query = db.deserialize(serialized)

That should be doable, but the type of db.deserialize(serialized) would obviously be wrong, since we can't deserialize the type from just a string. The deserialized query would be something like QueryBuilder<DB, any, unknown>.

I don't think we should override toString(). People would assume toString() returns the SQL and fromString parses SQL into a QueryBuilder.

You can already serialize the query like this:

const serialized = JSON.stringify(query.toOperationNode())

[steida]

Yes, only the query.

Agreed, toString is too invasive. JSON is better, yes.

toOperation node is probably good enough, maybe we don't need deserialization at all. Will check it.

Thank you for the answer.

[steida]

@koskimas Is there an interface representing a valid SQL? To detect:

db.selectFrom('thing') not valid
db.selectFrom('thing').selectAll() valid, toOperationNode can be called.

[steida]

Hmm, forget about it. It's specialized case. I don't want to distract you.