Using SQL databases

Provisioning, migrating, querying

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

Creating a database

To create a database, import and call new SQLDatabase, assigning the result to a top-level variable.

For example:

import { SQLDatabase } from ""; // 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 when starting encore run (locally) or on the next deployment (in the cloud). 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.

Defining the database schema

Database schemas are defined by creating migration files in a directory named migrations within an Encore service package. Each migration file is named <number>_<name>.up.sql, where <number> is a sequence number for ordering the migrations and <name> is a descriptive name of what the migration does.

On disk it might look like this:

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

Each migration runs in order and expresses the change in the database schema from the previous migration.

The file name format is important. Migration files must start with a number followed by _, and increasing for each migration. Each file name must also end with .up.sql.

The simplest naming convention is to start from 1 and counting up:

  • 1_first_migration.up.sql
  • 2_second.up.sql
  • 3_migration_name_goes_here.up.sql
  • ... and so on.

It's also possible to prefix the migration files with leading zeroes to have them ordered nicer in the editor (like 0001_migration.up.sql).

The first migration usually defines the initial table structure. For example, a todo service might start out by creating todo/migrations/1_create_table.up.sql with the following contents:


Provisioning databases

Encore automatically provisions databases to match what your application requires. When you define a database, Encore will provision the database at your next deployment.

Encore provisions databases in an appropriate way depending on the environment. When running locally, Encore creates a database cluster using Docker. In the cloud, it depends on the environment type:

  • In production environments, the database is provisioned through the Managed SQL Database service offered by the chosen cloud provider.
  • In development environments, the database is provisioned as a Kubernetes deployment with a persistent disk attached.

See exactly what is provisioned for each cloud provider, and each environment type, in the infrastructure documentation.

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.query`SELECT title FROM todo_item WHERE id = ${id}`; return row?.title; }

Inserting data

To insert data, or to make database queryies 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.

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 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 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.

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.


Application won't run

When you run your application locally with encore run, Encore will parse and compile your application, and provision the necessary infrastructure including databases. If this fails with a database error, there are a few common causes.

Error: sqldb: unknown database

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

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.