Prisma Engines

This repository contains a collection of engines that power the core stack for Prisma, most prominently Prisma Client and Prisma Migrate.

If you're looking for how to install Prisma or any of the engines, the Getting Started guide might be useful.

This document describes some of the internals of the engines, and how to build and test them.

What's in this repository

This repository contains four engines:

• Query engine, used by the client to run database queries from Prisma Client
• Migration engine, used to create and run migrations
• Introspection engine, used to get the state of the database, compare it to the schema file, and figure out what the differences are
• Prisma Format, used to format prisma files

Additionally, the psl (Prisma Schema Language) is the library that defines how the language looks like, how it's parsed, etc.

You'll also find:

• libs, for various (small) libraries such as macros, user facing errors, various connector/database-specific libraries, etc.
• a docker-compose.yml file that's helpful for running tests and bringing up containers for various databases
• a flake.nix file for bringing up all dependencies and making it easy to build the code in this repository (the use of this file and nix is entirely optional, but can be a good and easy way to get started)
• an .envrc file to make it easier to set everything up, including the nix shell

Documentation

The API docs (cargo doc) are published on our fabulous repo page.

Building Prisma Engines

Prerequisites:

• Installed the stable Rust toolchain, at least version 1.52.0. You can get the toolchain at rustup or the package manager of your choice.
• Linux only: OpenSSL is required to be installed.
• Installed direnv, then direnv allow on the repository root.
  • Make sure direnv is hooked into your shell
  • Alternatively: Load the defined environment in ./.envrc manually in your shell.
• For m1 users: Install Protocol Buffers

Note for nix users: it should be enough to direnv allow. How to build:

To build all engines, simply execute cargo build on the repository root. This builds non-production debug binaries. If you want to build the optimized binaries in release mode, the command is cargo build --release.

Depending on how you invoked cargo in the previous step, you can find the compiled binaries inside the repository root in the target/debug (without --release) or target/release directories (with --release):

Prisma Component	Path to Binary
Query Engine	./target/[debug|release]/query-engine
Migration Engine	./target/[debug|release]/migration-engine
Introspection Engine	./target/[debug|release]/introspection-engine
Prisma Format	./target/[debug|release]/prisma-fmt

Prisma Schema Language

The Prisma Schema Language is a library which defines the data structures and parsing rules for prisma files, including the available database connectors. For more technical details, please check the library README.

The PSL is used throughout the migration and introspection engines, as well as prisma format. The DataModeL (DML), which is an annotated version of the PSL is also used as input for the query engine.

Query Engine

The Query Engine is how Prisma Client queries are executed. Here's a brief description of what it does:

• takes as inputs an annotated version of the Prisma Schema file called the DataModeL (DML),
• using the DML (specifically, the datasources and providers), it builds up a GraphQL model for queries and responses,
• runs as a server listening for GraphQL queries,
• it translates the queries to the respective native datasource(s) and returns GraphQL responses, and
• handles all connections and communication with the native databases.

When used through the Prisma Client, there are two ways for the Query Engine to be executed:

• as a binary, downloaded during installation, launched at runtime; communication happens via HTTP (./query-engine/query-engine)
• as a native, platform-specific Node.js addon; also downloaded during installation (./query-engine/query-engine-node-api)

Usage

You can also run the Query Engine as a stand-alone GraphQL server.

Warning: There is no guaranteed API stability. If using it on production please be aware the api and the query language can change any time.

Notable environment flags:

• RUST_LOG_FORMAT=(devel|json) sets the log format. By default outputs json.
• QE_LOG_LEVEL=(info|debug|trace) sets the log level for the Query Engine. If you need Query Graph debugging logs, set it to "trace"
• FMT_SQL=1 enables logging formatted SQL queries
• PRISMA_DML_PATH=[path_to_datamodel_file] should point to the datamodel file location. This or PRISMA_DML is required for the Query Engine to run.
• PRISMA_DML=[base64_encoded_datamodel] an alternative way to provide a datamodel for the server.
• RUST_BACKTRACE=(0|1) if set to 1, the error backtraces will be printed to the STDERR.
• LOG_QUERIES=[anything] if set, the SQL queries will be written to the INFO log. Needs the right log level enabled to be seen from the terminal.
• RUST_LOG=[filter] sets the filter for the logger. Can be either trace, debug, info, warning or error, that will output ALL logs from every crate from that level. The .envrc in this repo shows how to log different parts of the system in a more granular way.

Starting the Query Engine:

The engine can be started either with using the cargo build tool, or pre-building a binary and running it directly. If using cargo, replace whatever command that starts with ./query-engine with cargo run --bin query-engine --.

You can also pass --help to find out more options to run the engine.

Metrics

Running make show-metrics will start Prometheus and Grafana with a default metrics dashboard. Prometheus will scrape the /metrics endpoint to collect the engine's metrics

Navigate to http://localhost:3000 to view the Grafana dashboard.

Migration Engine

The Migration Engine does a couple of things:

• creates new migrations by comparing the prisma file with the current state of the database, in order to bring the database in sync with the prisma file
• run these migrations and keeps track of which migrations have been executed

The engine uses:

• the prisma files, as the source of truth
• the database it connects to, for diffing and running migrations, as well as keeping track of migrations in the _prisma_migrations table
• the prisma/migrations directory which acts as a database of existing migrations

For more information about the migrations engine, check the crate README.

Introspection Engine

The Introspection Engine is able to (re-)generate a prisma file starting from a live database.

In a way, it's the opposite of the migration engine: whereas the migration engine uses the prisma file as the source of truth to update the database, the introspection engine reverses that dependency. It inspects the database, and generates a prisma schema file as a result.

For more information about the introspection engine, check the crate README .

Prisma format

Prisma format can format prisma schema files. It also comes as a WASM module via a node package. You can read more here.

Debugging

When trying to debug code, here's a few things that might be useful:

• use the language server; being able to go to definition and reason about code can make things a lot easier,
• add dbg!() statements to validate code paths, inspect variables, etc.,
• you can control the amount of logs you see, and where they come from using the RUST_LOG environment variable; see the documentation,
• you can use the test-cli to test migration and introspection without having to go through the prisma npm package.

Testing

There are two test suites for the engines: Unit tests and integration tests.

• Unit tests: They test internal functionality of individual crates and components.

  You can find them across the whole codebase, usually in ./tests folders at the root of modules. These tests can be executed via cargo test. Note that some of them will require the TEST_DATABASE_URL enviornment variable set up.

• Integration tests: They run GraphQL queries against isolated instances of the Query Engine and asserts that the responses are correct.

  You can find them at ./query-engine/connector-test-kit-rs.

Set up & run tests:

Prerequisites:

• Installed Rust toolchain.
• Installed Docker.
• Installed direnv, then direnv allow on the repository root.
  • Alternatively: Load the defined environment in ./.envrc manually in your shell.

Setup: There are helper make commands to set up a test environment for a specific database connector you want to test. The commands set up a container (if needed) and write the .test_config file, which is picked up by the integration tests:

• make dev-mysql: MySQL 5.7
• make dev-mysql8: MySQL 8
• make dev-postgres: PostgreSQL 10
• make dev-sqlite: SQLite
• make dev-mongodb_5: MongoDB 5

*On windows: If not using WSL, make is not available and you should just see what your command does and do it manually. Basically this means editing the .test_config file and starting the needed Docker containers.

To actually get the tests working, read the contents of .envrc. Then Edit environment variables for your account from Windows settings, and add at least the correct values for the following variables:

• WORKSPACE_ROOT should point to the root directory of prisma-engines project.
• PRISMA_BINARY_PATH is usually %WORKSPACE_ROOT%\target\release\query-engine.exe.
• MIGRATION_ENGINE_BINARY_PATH should be %WORKSPACE_ROOT%\target\release\migration-engine.exe.

Other variables may or may not be useful.

Run:

Run cargo test in the repository root.

Parallel rust-analyzer builds

When rust-analzyer runs cargo check it will lock the build directory and stop any cargo commands from running until it has completed. This makes the build process feel a lot longer. It is possible to avoid this by setting a different build path for rust-analyzer. To avoid this. Open VSCode settings and search for Check on Save: Extra Args. Look for the Rust-analyzer › Check On Save: Extra Args settings and add a new directory for rust-analyzer. Something like:

--target-dir:/tmp/rust-analyzer-check

Automated integration releases from this repository to npm

(Since July 2022). Any branch name starting with integration/ will, first, run the full test suite and, second, if passing, run the publish pipeline (build and upload engines to S3)

The journey through the pipeline is the same as a commit on the main branch.

• It will trigger prisma/engines-wrapper and publish a new @prisma/engines-version npm package but on the integration tag.
• Which triggers prisma/prisma to create a chore(Automated Integration PR): [...] PR with a branch name also starting with integration/
• Since in prisma/prisma we also trigger the publish pipeline when a branch name starts with integration/, this will publish all prisma/prisma monorepo packages to npm on the integration tag.
• Our ecosystem-tests tests will automatically pick up this new version and run tests, results will show in GitHub Actions

This end to end will take minimum ~1h20 to complete, but is completely automated 🤖

Notes:

• in prisma/prisma repository, we do not run tests for integration/ branches, it is much faster and also means that there is no risk of test failing (e.g. flaky tests, snapshots) that would stop the publishing process.
• in prisma/prisma-engines tests must first pass, before publishing starts. So better keep an eye on them and restart them as needed.

Security

If you have a security issue to report, please contact us at [email protected]