Using SQL databases

Encore treats SQL databases as logical resources and natively supports PostgreSQL databases.

Creating a database

To create a database, import encore.dev/storage/sqldb and call new SQLDatabase, assigning the result to a top-level variable. Use a migration file in a directory migrations to define the database schema.

For example:

todo/todo.ts
todo/migrations/1_create_table.up.sql
import { SQLDatabase } from "encore.dev/storage/sqldb";

// Create the todo database and assign it to the "db" variable
const db = new SQLDatabase("todo", {
  migrations: "./migrations",
});

// Then, query the database using db.query, db.exec, etc.

As seen above, the new SQLDatabase() call takes two parameters: the name of the database, and a configuration object. The configuration object specifies the directory containing the database migration files, which is how you define the database schema.

See the Defining the database schema section below for more details.

With this code in place, Encore will automatically create the database using Docker when you run the command encore run in your local environment. Make sure Docker is installed and running on your machine before running encore run.

In cloud environments, Encore automatically injects the appropriate configuration to authenticate and connect to the database, so once the application starts up the database is ready to be used.

Database Migrations

Encore automatically handles up migrations, while down migrations must be run manually. Each up migration runs sequentially, expressing changes in the database schema from the previous migration.

Naming Conventions

File Name Format: Migration files must start with a number followed by an underscore (_), and must increase sequentially. Each file name must end with .up.sql.

Examples:

• 1_first_migration.up.sql
• 2_second_migration.up.sql
• 3_migration_name.up.sql

You can also prefix migration files with leading zeroes for better ordering in the editor (e.g., 0001_migration.up.sql).

Defining the Database Schema

The first migration typically defines the initial table structure. For instance, a todo service might create todo/migrations/1_create_table.up.sql with the following content:

CREATE TABLE todo_item (
    id BIGSERIAL PRIMARY KEY,
    title TEXT NOT NULL,
    done BOOLEAN NOT NULL DEFAULT false
);

Migration File Structure

Migration files are created in a migrations directory within an Encore service. Each file is named <number>_<name>.up.sql, where <number> is a sequence number for ordering and <name> describes the migration.

Example Directory Structure:

/my-app
├── encore.app                       // ... other top-level project files
│
└── todo                             // todo service
    ├── migrations                   // database migrations (directory)
    │   ├── 1_create_table.up.sql    // first migration file
    │   └── 2_add_field.up.sql       // second migration file
    ├── todo.ts                      // todo service code
    └── todo.test.ts                 // tests for todo service

Using databases

Once you have created the database using const db = new SQLDatabase(...) you can start querying and inserting data into the database by calling methods on the db variable.

Querying data

To query data, use the db.query or db.queryRow methods. db.query returns an asynchronous iterator, yielding rows one by one as they are streamed from the database. queryRow returns a single row, or null if the query yields no rows.

Both APIs operate using JavaScript template strings, allowing easy use of placeholder parameters while preventing the possibility of SQL Injection vulnerabilities.

Typical usage looks like this:

const allTodos = await db.query`SELECT * FROM todo_item`;
for await (const todo of allTodos) {
  // Process each todo
}

Or to query a single todo item by id:

async function getTodoTitle(id: number): string | undefined {
  const row = await db.queryRow`SELECT title FROM todo_item WHERE id = ${id}`;
  return row?.title;
}

Inserting data

To insert data, or to make database queries that don't return any rows, use db.exec.

For example:

await db.exec`
  INSERT INTO todo_item (title, done)
  VALUES (${title}, false)
`;

Connecting to databases

It's often useful to be able to connect to the database from outside the backend application. For example for scripts, ad-hoc querying, or dumping data for analysis.

Currently Encore does not expose user credentials for databases in the local environment or for environments on Encore Cloud. You can use a connection string to connect instead, see below.

Using the Encore CLI

Encore's CLI comes with built-in support for connecting to databases:

• encore db shell <database-name> [--env=<name>] opens a psql shell to the database named <database-name> in the given environment. Leaving out --env defaults to the local development environment. encore db shell defaults to read-only permissions. Use --write, --admin and --superuser flags to modify which permissions you connect with.

• encore db conn-uri <database-name> [--env=<name>] outputs a connection string for the database named <database-name>. When specifying a cloud environment, the connection string is temporary. Leaving out --env defaults to the local development environment.

• encore db proxy [--env=<name>] sets up a local proxy that forwards any incoming connection to the databases in the specified environment. Leaving out --env defaults to the local development environment.

See encore help db for more information on database management commands.

Using database user credentials

For cloud environments on AWS/GCP you can view database user credentials (created by Encore when provisioning databases) via the Cloud Dashboard:

• Open your app in the Cloud Dashboard, navigate to the Infrastructure page for the appropriate environment, and locate the USERS section within the relevant Database Cluster.

Handling migration errors

When Encore applies database migrations, there's always a possibility the migrations don't apply cleanly.

This can happen for many reasons:

• There's a problem with the SQL syntax in the migration
• You tried to add a UNIQUE constraint but the values in the table aren't actually unique
• The existing database schema didn't look like you thought it did, so the database object you tried to change doesn't actually exist
• ... and so on

If that happens, Encore rolls back the migration. If it happens during a cloud deployment, the deployment is aborted. Once you fix the problem, re-run encore run (locally) or push the updated code (in the cloud) to try again.

Encore tracks which migrations have been applied in the schema_migrations table:

database=# \d schema_migrations
          Table "public.schema_migrations"
 Column  |  Type   | Collation | Nullable | Default
---------+---------+-----------+----------+---------
 version | bigint  |           | not null |
 dirty   | boolean |           | not null |
Indexes:
    "schema_migrations_pkey" PRIMARY KEY, btree (version)

The version column tracks which migration was last applied. If you wish to skip a migration or re-run a migration, change the value in this column. For example, to re-run the last migration, run UPDATE schema_migrations SET version = version - 1;. Note that Encore does not use the dirty flag by default.

Using an ORM

Encore has all the tools needed to support ORMs and migration frameworks out-of-the-box through named databases and migration files. Writing plain SQL might not work for your use case, or you may not want to use SQL in the first place.

ORMs like Prisma and Drizzle can be used with Encore by integrating their logic with a system's database. Encore is not restrictive, it uses plain SQL migration files for its migrations.

• If your ORM of choice can connect to any database using a standard SQL driver, then it can be used with Encore.
• If your migration framework can generate SQL migration files without any modifications, then it can be used with Encore.

For more information on using ORMs with Encore, see the ORMs page.

PostgreSQL Extensions

Encore uses the encoredotdev/postgres docker image for local development, CI/CD, and for databases hosted on Encore Cloud.

This docker image ships with many popular PostgreSQL extensions pre-installed. In particular, pgvector and PostGIS are available.

See the full list of available extensions.

Troubleshooting

When you run your application locally with encore run, Encore will provision local databases using Docker. If this fails with a database error, it can often be resolved if you restart the Encore daemon using encore daemon and then try encore run again.

If this does not resolve the issue, here are steps to resolve common errors:

Error: sqldb: unknown database

This error is often caused by a problem with the initial migration file, such as incorrect naming or location.

• Verify that you've created the migration file correctly, then try encore run again.

Error: could not connect to the database

When you can't connect to the database in your local environment, there's likely an issue with Docker:

• Make sure that you have Docker installed and running, then try encore run again.
• If this fails, restart the Encore daemon by running encore daemon, then try encore run again.

Error: Creating PostgreSQL database cluster Failed

This means Encore was not able to create the database. Often this is due to a problem with Docker.

• Check if you have permission to access Docker by running docker images.
• Set the correct permissions with sudo usermod -aG docker $USER (Learn more in the Docker documentation)
• Then log out and log back in so that your group membership is refreshed.

Error: unable to add CA to cert pool

This error is commonly caused by the presence of the file $HOME/.postgresql/root.crt on the filesystem. When this file is present the PostgreSQL client library will assume the database server has that root certificate, which will cause the above error.

• Remove or rename the file, then try encore run again.