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Meltano 3.0 Migration Guide

The following list includes all recommended migration tasks as well as breaking changes in Meltano version 3.0.0.

Changed​

Using Postgres as a backend now requires installing Meltano with extra components​

If you are already using Postgres as a backend, odds are you rely on Meltano's dependency on psycopg2, so you will need to install Meltano with the psycopg2 extra:

pipx install "meltano[psycopg2]"

If you are setting a Postgres backend for the first time, it's recommended to instead use the postgres extra and use the postgresql+psycopg URI scheme:

pipx install "meltano[postgres]"
meltano config meltano set database_uri postgresql+psycopg://<username>:<password>@<host>:<port>/<database>

Plugin lock files are now always required​

Plugin lock files are now always required.

Before this, Meltano fell back to retrieving the plugin definition from Meltano Hub if the lock file was missing. This behavior caused issues when lock files were not deployed to production and Meltano Hub was unavailable because of network restrictions.

Migration steps​

  1. Enable the ff.plugin_locks_required feature flag:
meltano config meltano set ff.plugin_locks_required true
  1. Test that your project still works as expected. For example, by installing all plugins:
meltano install
  1. Generate all lock files for your project:
meltano lock --all
  1. (Optional) Remove the ff.plugin_locks_required feature flag after upgrading to Meltano v3, since it has no effect in Meltano v3.

For custom plugins, you might need to add a namespace to the plugin definition.

Removed​

Target extra setting target_schema​

In line with the deprecation of the meltano elt command in favor of meltano el, the target_schema extra setting of loaders has been removed.

This should impact very few users, as the target_schema extra setting was only used by the dbt transformer, which has been deprecated in favor of adapter-specific dbt utilities.

Migration steps​

  1. In the configuration for the dbt transformer plugin, set the source_schema value to the appropriate environment variable for your target (e.g. $MELTANO_LOAD__DEFAULT_TARGET_SCHEMA for Postgres).

The Meltano UI​

Before Meltano v3.0.0, Meltano included a web-UI that could be hosted by running meltano ui. In Meltano v2.12.0, this UI was deprecated. In Meltano v3.0.0, this UI has been removed. Everything that was possible through the UI is possible without it via the CLI, or by directly editing meltano.yml.

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