Operations: How to Configure Revisions

The ConfigureRevisionsOperation modifies the revisions settings for a particular database. Within that database, each collection can have its own separate revisions settings.

To configure the revisions settings for a database and/or the collections in that database, follow these steps:

1. Create a RevisionsCollectionConfiguration object for each desired collection.
2. Put those RevisionsCollectionConfiguration objects in a RevisionsConfiguration object.
3. Send that RevisionsConfiguration to the server.

RevisionsCollectionConfiguration

This object contains the four revisions settings for a particular collection:

public class RevisionsCollectionConfiguration
{
    private boolean disabled;
    private Duration minimumRevisionAgeToKeep;
    private Long minimumRevisionsToKeep;
    private boolean purgeOnDelete;
}

A revision is only deleted if both the minimumRevisionsToKeep for that document is exceeded, and the revision is older than the minimumRevisionAgeToKeep limit. The oldest revisions are deleted first.

• By default both these options are set to null, meaning that an unlimited number of revisions will be saved indefinitely.

• If only minimumRevisionsToKeep is null, revisions will be deleted only when they are older than minimumRevisionAgeToKeep.

• If only minimumRevisionAgeToKeep is null, revisions will be deleted each time there are more revisions than minimumRevisionsToKeep.

These deletions will only take place when a new revision is added to a document. Until a new revision is added, that document's revisions can exceed these limits.

RevisionsConfiguration

This object contains a Map of revision configurations for each collection in the database, plus an optional default configuration.

public class RevisionsConfiguration
{
     private Map<String, RevisionsCollectionConfiguration> collections;
     private RevisionsCollectionConfiguration defaultConfig;
}

Note that when this object is sent to the server, it overrides the configurations for all collections, including all existing configurations currently on the server. If a collection is not listed in collections and defaultConfig has not been set, the default values listed in the table above are applied.

ConfigureRevisionsOperation

Lastly, the operation itself sends the RevisionsConfiguration to the server, overriding all existing collection configurations. You'll want to store these configurations on the client side so they don't have to be created from scratch each time you want to modify them.

public ConfigureRevisionsOperation(RevisionsConfiguration configuration);

The following code sample updates the settings of the Document Store's default database - which in this case is a database named "Northwind". To update the configuration of different database, use the forDatabase() method.

// Create a configuration for the Employees collection
RevisionsCollectionConfiguration employeesRevConfig = new RevisionsCollectionConfiguration();
employeesRevConfig.setMinimumRevisionAgeToKeep(Duration.ofDays(1));
employeesRevConfig.setMinimumRevisionsToKeep(42l);
employeesRevConfig.setPurgeOnDelete(true);

// Add the Employees configuration to a map
Map<String, RevisionsCollectionConfiguration> collections = new HashMap<>();
collectionConfig.put("Employees", employeesRevConfig);

// Create a default collection configuration
RevisionsCollectionConfiguration defaultRevConfig = new RevisionsCollectionConfiguration();
defaultRevConfig.setMinimumRevisionAgeToKeep(Duration.ofDays(7));
defaultRevConfig.setMinimumRevisionsToKeep(100l);
defaultRevConfig.setPurgeOnDelete(false);

// Combine to create a configuration for the database
RevisionsConfiguration northwindRevConfig = new RevisionsConfiguration();
northwindRevConfig.setCollections(collections);
northwindRevConfig.setDefaultConfig(defaultRevConfig);

// Execute the operation to update the database
documentStore.maintenance().send(new ConfigureRevisionsOperation(northwindRevConfig));