Labels

Labels are tags that you can add to changesets to control which changeset will be executed in any migration run. Labels control whether a changeset is executed depending on runtime settings. Any string can be used for the label name, and it is case-insensitive.

Labels allow you to choose a subset of changesets to execute at the runtime and represent a simple list on each changeset and complex expressions that are supplied at the runtime. It means that changesets are tagged with a list of labels (not expressions), and during the runtime, you can pass a label expression to choose the changesets which match the expression.

Uses

You can typically use labels to:

  • Manage and track your deployments.
  • Apply complex logic to your deployments.
  • Mark changesets based on features and then selectively apply those features at the execution time instead of using version control branches.
  • Use different languages for marking changesets. For example, you can mark your changesets both with Spanish and English.

Labels runtime syntax

Labels can be specified using AND, OR, !, and () (parentheses that are used for grouping). For example:

  • --labels="!v.0.1"
  • --labels="v.1.0 and v.1.1"
  • --labels="v.1.0 or v.1.1"
  • --labels="!v.1.0 and !v.1.1"

Using "," to separate labels works the same as an OR operation. For example:

  • --labels="v.1.0, v.1.1" is the same as --labels="v.1.0 OR v.1.1"
  • --labels="v.0.1, v.1.0 and v.1.1" is the same as --labels="(v.0.1) OR (v.1.0 and v.1.1)"

You can run the --labels attribute to determine which changesets in the changelog to evaluate based on its label.

  • In your changelog, you can specify only a simple list of labels to apply to the changeset. For example, labels="v.0.1, v.1.0".
  • At runtime, you can specify a complex expression with the labels that you want to execute. For example, --labels="!v.0.1" or --labels="v.1.0 or (v.1.1 and v.1.2)".

How to work with labels

It is best practice to enumerate your changesets or describe what a changeset is used for. An example of labels indicating the version or a specific feature can be "1.0" or "shopping_cart". In this case, labels will allow you to run changes with:

  • --labels=1.0 to deploy the 1.0 changesets or --labels=shopping_cart to deploy the changesets related to the shopping cart.
  • --labels="1.0 or (1.1 and shopping_cart)" to deploy the 1.0 changesets and only the 1.1. features related to the shopping cart.
  • --labels="1.0 or (1.1 and !shopping_cart)" to deploy the 1.0 changesets and the 1.1. features that are not related to the shopping cart.

You can see an example of running the update command with complex label statements:

liquibase --changeLogFile=changelog.xml --outputFile=update.txt --labels="1.0 or (1.1 and !shopping_cart)" update

If your changelog includes changesets that have labels and changesets that don't have them, changesets without labels will match any label.

Example: If you run the liquibase --labels=release3 update command, it will deploy all changesets with the label release3 and all changesets without any label.