Attaching to external Kuzu databases

Using the ATTACH statement, you can connect to an external Kuzu database. The external Kuzu database can be local or remote, e.g., in an S3 bucket. Attaching to a local Kuzu database does not require installing any extensions. Attaching to a remote Kuzu database requires installing the httpfs extension. Aside from this requirement of installing the httpfs extension, attaching to a local vs. remote Kuzu database work the same. So, we only document how to attach to a remote Kuzu database here.

As a first step, you need to install the httpfs extension with the following commands:

INSTALL httpfs;
LOAD EXTENSION httpfs;

Then you use the ATTACH statement to attach to a remote Kuzu database. The basic syntax is as follows:

ATTACH [DB_PATH] AS [alias] (dbtype kuzu)

DB_PATH: Path to the (remote) database directory (can either be an S3, GCS or HTTP URL)
alias: Database alias to use. Aliases are mandatory for attaching to external Kuzu databases.

You can list all the databases you have attached to by running the following command:

CALL SHOW_ATTACHED_DATABASES() RETURN *;

Unlike attaching to external RDBMSs, the alias is not used as a prefix of node and relationship tables. This is because at any point in time, you can attach to a single external Kuzu database (or be connected to the local Kuzu database you opened at the beginning of your session). Therefore you don’t need to prefix your node and relationship tables. Instead you will use the alias to DETACH from the external Kuzu database.

Suppose you are connected to a local database ./demo_db. The below example shows how the Kuzu database hosted on S3 directory 's3://kuzu-example/university can be attached to using the alias uw.

If you wish to attach to a database hosted on GCS instead, just replace the prefix s3:// with gs:// (in this case it would become 'gs://kuzu-example/university). For more information on how to set up Kuzu with GCS, see here.

ATTACH 's3://kuzu-example/university' AS uw (dbtype kuzu);

After attaching a remote Kuzu database, you no longer have access to the original local Kuzu database ./demo_db. After the ATTACH statement above, you can only query the external Kuzu database under s3://kuzu-example/university.

Execute queries on external Kuzu database.

We only allow read-only queries to execute on external Kuzu database (even if the external database is stored on local disk).

MATCH (p:Person) RETURN p.name AS name, p.age AS age;

Result:

┌────────┬───────┐
│ name   │ age   │
│ STRING │ INT64 │
├────────┼───────┤
│ Alice  │ 30    │
│ Bob    │ 27    │
│ Carol  │ 19    │
│ Dan    │ 25    │
└────────┴───────┘

Detaching from a remote Kuzu database

You can detach from an external Kuzu database by using the DETACH [ALIAS] statement as follows:

DETACH uw

After the DETACH statement, you can continue querying your local Kuzu database ./demo_db. Therefore, detaching from an external Kuzu database switches your Kuzu database to become the local database you had started your session with.

Using local cache for remote files

When connecting to a remote external Kuzu database, say the 's3://kuzu-example/university database in our example above, you would use the httpfs extension. When querying this remote database in Cypher, Kuzu will make HTTPS calls to the remote server to query this database. Similar to how you can speed up LOAD FROM queries using the local httpfs cache for scanning remote files, you can also speed up your Cypher queries by using the local httpfs cache. You can enable the local cache by running CALL HTTP_CACHE_FILE=TRUE; after installing the httpfs extension and before attaching to the remote Kuzu database.