Databases

Working with Couchbase Lite databases

Database Concepts

Databases created on Couchbase Lite can share the same hierarchical structure as Couchbase Server or Capella databases. This makes it easier to sync data between mobile applications and applications built using Couchbase Server or Capella.

Figure 1. Couchbase Lite Database Hierarchy

Although the terminology is different, the structure can be mapped to relational database terms:

Table 1. Relational Database → Couchbase

Relational database	Couchbase
Database	Database
Schema	Scope
Table	Collection

This structure gives you plenty of choices when it comes to partitioning your data. The most basic structure is to use the single default scope with a single default collection; or you could opt for a structure that allows you to split your collections into logical scopes.

Figure 2. Couchbase Lite Examples

Storing local configuration

You may not need to sync all the data related for a particular application. You can set up a scope that syncs data, and a second scope that doesn’t.

One reason for doing this is to store local configuration data (such as the preferred screen orientation or keyboard layout). Since this information only relates to a particular device, there is no need to sync it:

local data scope	Contains information pertaining to the device.
syncing data scope	Contains information pertaining to the user, which can be synced back to the cloud for use on the web or another device.

Create or Open Database

You can create a new database and-or open an existing database, using the Database class. Just pass in a database name and optionally a DatabaseConfiguration — see Example 1.

Things to watch for include:

• If the named database does not exist in the specified, or default, location then a new one is created
• The database is created in a default location unless you specify a directory for it — see DatabaseConfiguration and DatabaseConfiguration.setDirectory()

Tip

Best Practice is to always specify the path to the database explicitly.

Typically, the default location is the application sandbox or current working directory.

See also Finding a Database File.

Example 1. Open or create a database

val database = Database(
    "my-db",
    DatabaseConfigurationFactory.newConfig(
        "path/to/database"
    )
)

Tip

"path/to/database" might be a platform-specific location. Use expect/actual or dependency injection to provide a platform-specific database path.

Close Database

You are advised to incorporate the closing of all open databases into your application workflow.

Closing a database is simple, just use Database.close() — see Example 2. This also closes active replications, listeners and-or live queries connected to the database.

Note

Closing a database soon after starting a replication involving it can cause an exception as the asynchronous replicator (start) may not yet be connected.

Example 2. Close a Database

database.close()

Database Encryption

This is an Enterprise Edition feature.

Kotbase includes the ability to encrypt Couchbase Lite databases. This allows mobile applications to secure the data at rest, when it is being stored on the device. The algorithm used to encrypt the database is 256-bit AES.

Enabling

To enable encryption, use DatabaseConfiguration.setEncryptionKey() to set the encryption key of your choice. Provide this encryption key every time the database is opened — see Example 3.

Example 3. Configure Database Encryption

val db = Database(
    "my-db",
    DatabaseConfigurationFactory.newConfig(
        encryptionKey = EncryptionKey("PASSWORD")
    )
)

Persisting

Couchbase Lite does not persist the key. It is the application’s responsibility to manage the key and store it in a platform specific secure store such as Apple’s Keychain or Android’s Keystore.

Opening

An encrypted database can only be opened with the same language SDK that was used to encrypt it in the first place. So a database encrypted with Kotbase on Android (which uses the Couchbase Lite Android SDK) and then exported, is readable only by Kotbase on Android or the Couchbase Lite Android SDK.

Changing

To change an existing encryption key, open the database using its existing encryption-key and use Database.changeEncryptionKey() to set the required new encryption-key value.

Removing

To remove encryption, open the database using its existing encryption-key and use Database.changeEncryptionKey() with a null value as the encryption key.

Finding a Database File

Android

When the application is running on the Android emulator, you can locate the application’s data folder and access the database file by using the adb CLI tools. For example, to list the different databases on the emulator, you can run the following commands.

Example 4. List files

$ adb shell
$ su
$ cd /data/data/{APPLICATION_ID}/files
$ ls

The adb pull command can be used to pull a specific database to your host machine.

Example 5. Pull using adb command

$ adb root
$ adb pull /data/data/{APPLICATION_ID}/files/{DATABASE_NAME}.cblite2 .

iOS

When the application is running on the iOS simulator, you can locate the application’s sandbox directory using the OpenSim utility.

Database Maintenance

From time to time it may be necessary to perform certain maintenance activities on your database, for example to compact the database file, removing unused documents and blobs no longer referenced by any documents.

Couchbase Lite’s API provides the Database.performMaintenance() method. The available maintenance operations, including compact are as shown in the enum MaintenanceType to accomplish this.

This is a resource intensive operation and is not performed automatically. It should be run on-demand using the API. If in doubt, consult Couchbase support.

Command Line Tool

cblite is a command-line tool for inspecting and querying Couchbase Lite databases.

You can download and build it from the couchbaselabs GitHub repository.

Troubleshooting

You should use console logs as your first source of diagnostic information. If the information in the default logging level is insufficient you can focus it on database errors and generate more verbose messages — see Example 6.

For more on using Couchbase logs — see Using Logs.

Example 6. Increase Level of Database Log Messages

Database.log.console.domains = setOf(LogDomain.DATABASE)