Support MongoDB "query" logging

[matthewmueller]

Problem

Right now we don't have a way to log the underlying querying run against a MongoDB database. This will be important because the Prisma way of querying is higher-level than the database query and often it's not clear how you'd map a Prisma query to the underlying query.

Suggested Solution

We already support with other databases via

const prisma = new PrismaClient({
  log: ['query'],
})

We should investigate supporting this for MongoDB too. One possible suggestion would be to see how other ORMs like Mongoose do logging.

[matthewmueller]

Looks like it's possible to send queries from the MongoDB driver with https://docs.rs/mongodb/latest/mongodb/event/command/trait.CommandEventHandler.html

Internal Context: https://prisma-company.slack.com/archives/C0239SYUZV1/p1645130088849539

[matthewmueller]

Talked with @janpio a bit about it and here's an idea that might be simpler that's more similar to what we currently do with logging SQL queries.

Before each of the mongodb driver calls, we serialize into a JSON log. Something like:

logger.query(JSON.stringify({
  findOne: "Pets",
  document: document
}))

// Actual driver call
driver.db("Pets").findOne(document)

This isn't going to be a standard MongoDB log, but they don't really have a standard. I think we could use the same format we have for $runCommandRaw.

As with SQL, this logger would be enabled by:

const prisma = new PrismaClient({
  log: ['query'],
})

---

Goal is to help people understand the underlying queries were run. Bonus points if you can copy and paste it somewhere without changing the format, so it's easier to test the query manually.

I prefer what @dpetrick mentioned about having it be in the format of the mongodb shell over the $runCommandRaw described above, but $runCommandRaw format (or some other logical format) would be fine too.

It does seem like we'll need some way to deal with newlines in the queries and newlines as separators. For that, I can share what I've used before: http://ndjson.org/, but I don't have an opinion on this.

[matthewmueller]

• Have a quick kickoff
• Decide on the MongoDB format

[cprieto]

We will be using something that would be useful for the mongo shell. Other libraries (like Mongoose) use a similar approach.