Database migrations

Langflow stores application data such as flows, users, and API keys in a SQL database.

When you upgrade Langflow or connect to a new empty database, Langflow must keep the database schema aligned with the application models.

By default, the Langflow database uses SQLite, and uses Alembic for SQL database migrations.

This page explains when migrations run and how to run and repair migrations safely.

Default migrations behavior and triggers

Most Langflow users never need to run a database migration. When you start Langflow, or restart a container after upgrading the Langflow image, pending Alembic migrations run as part of database initialization.

Langflow includes Alembic revision scripts with the package. On startup, Langflow connects to the database at LANGFLOW_DATABASE_URL or the default langflow.db file, ensures the required tables exist, checks the database schema against the current models, and then applies any pending Alembic upgrades to bring the schema to its head revision.

Alembic records the applied revision in the alembic_version table.

Other events that trigger Alembic checks are a first Langflow startup against a new SQLite file or empty PostgreSQL database, upgrading to a Langflow version that includes new Alembic revisions, or pointing LANGFLOW_DATABASE_URL at an empty database.

Upgrade Langflow safely

To upgrade Langflow or change the database URL in a deployment that already has data, you may need a database migration. To migrate your database, do the following:

Stop Langflow.
Back up the database.

If you're using SQLite, copy the langflow.db file. The default path depends on your install method and whether LANGFLOW_SAVE_DB_IN_CONFIG_DIR is set. For more information, see Memory management options.

If you're using PostgreSQL, make a logical backup with pg_dump, or use your database provider's snapshot. For more information, see enterprise backup guidance.
Export any flows you want to save as JSON. For more information, see Import and export flows.
Upgrade the Langflow package or container image to the latest version, keeping the same LANGFLOW_DATABASE_URL or the same SQLite path.
bash
```
uv pip install langflow -U
```
Start a single Langflow instance, so database migrations run without concurrent database writes.
Confirm that startup succeeds.
If startup reports a schema mismatch, run langflow migration to inspect the problem and restore from backup if needed. For more information, see langflow migration CLI.

Switch from SQLite to PostgreSQL

Changing LANGFLOW_DATABASE_URL from SQLite to PostgreSQL does not copy existing SQLite data into PostgreSQL. Langflow initializes and migrates the new database schema, and your previous SQLite file remains where it was.

There is no built-in SQLite-to-PostgreSQL data migrator. Langflow creates a new PostgreSQL schema, and then you can restore application data you saved.

To migrate your flows while switching from SQLite to PostgreSQL, do the following:

Export flows, and note any global variables or credentials.
Provision PostgreSQL 15+ and set LANGFLOW_DATABASE_URL as described in Configure an external PostgreSQL database.
If required, install PostgreSQL driver extras, for example uv pip install "langflow[postgresql]".
Start Langflow. The new PostgreSQL schema is created.
Import the exported flows and recreate secrets or variables as needed.

Migration logging

Alembic output is written to a log file by default at alembic/alembic.log under the Langflow config directory (LANGFLOW_CONFIG_DIR). Relative LANGFLOW_ALEMBIC_LOG_FILE values are also resolved against that config directory. In read-only or hardened containers, that path may not be writable, and Langflow will fall back to stdout and continue the migration.

Migration environment variables

Variable	Purpose
`LANGFLOW_ALEMBIC_LOG_TO_STDOUT`	Set to `true` to send Alembic migration output to `stdout`.
`LANGFLOW_ALEMBIC_LOG_FILE`	Absolute or relative path for the Alembic log file when not logging to `stdout`. Relative paths resolve under the Langflow config directory.
`LANGFLOW_MIGRATION_LOCK_TIMEOUT_S`	Seconds to wait for the PostgreSQL migration advisory lock. Default: `300`.
`LANGFLOW_MIGRATION_LOCK_NAMESPACE`	Optional namespace for the Alembic PostgreSQL advisory lock. The default lock key coordinates instances that share a database. Set this variable to isolate different Langflow deployments that share one PostgreSQL server. Use the same value on every instance in that deployment.

Troubleshooting

For troubleshooting database migrations, see Langflow upgrade issues.