ai.grakn.engine

Class SystemKeyspace

java.lang.Object

ai.grakn.engine.SystemKeyspace

public class SystemKeyspace
extends Object

Manages the system keyspace.

Used to populate the system schema the first time the system keyspace is created.

Used to populate the system keyspace with all newly create keyspaces as a user opens them. We have no way to determining whether a keyspace with a given name already exists or not. We maintain the list in our Grakn system keyspace. An element is added to that list when there is an attempt to create a graph from a factory bound to the keyspace name. The list is simply the instances of the system entity type 'keyspace'. Nothing is ever removed from that list. The set of known keyspaces is maintained in a static map so we don't connect to the system keyspace every time a factory produces a new graph. That means that we can't have several different factories (e.g. Janus and in-memory Tinkerpop) at the same time sharing keyspace names. We can't identify the factory builder by engineUrl and config because we don't know what's inside the config, which is residing remotely at the engine!

Author:

borislav, fppt

Field Summary

Fields

Modifier and Type	Field and Description
static ai.grakn.concept.Label	KEYSPACE_ENTITY
static ai.grakn.concept.Label	KEYSPACE_RESOURCE
static ai.grakn.Keyspace	SYSTEM_KB_KEYSPACE

Constructor Summary

Constructors

Constructor and Description
SystemKeyspace(EngineGraknTxFactory factory)
SystemKeyspace(EngineGraknTxFactory factory, boolean loadSystemSchema)

Method Summary

Modifier and Type	Method and Description
boolean	containsKeyspace(ai.grakn.Keyspace keyspace) Checks if the keyspace exists in the system.
boolean	deleteKeyspace(ai.grakn.Keyspace keyspace) This is called when a graph is deleted via GraknAdmin.delete().
boolean	ensureKeyspaceInitialised(ai.grakn.Keyspace keyspace) Notify that we just opened a keyspace with the same engineUrl & config.
void	loadSystemSchema() Load the system schema into a newly created system keyspace.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

SYSTEM_KB_KEYSPACE

public static final ai.grakn.Keyspace SYSTEM_KB_KEYSPACE

KEYSPACE_ENTITY

public static final ai.grakn.concept.Label KEYSPACE_ENTITY

KEYSPACE_RESOURCE

public static final ai.grakn.concept.Label KEYSPACE_RESOURCE

Constructor Detail

SystemKeyspace

public SystemKeyspace(EngineGraknTxFactory factory)

SystemKeyspace

public SystemKeyspace(EngineGraknTxFactory factory,
                      boolean loadSystemSchema)

Method Detail

ensureKeyspaceInitialised

public boolean ensureKeyspaceInitialised(ai.grakn.Keyspace keyspace)

Notify that we just opened a keyspace with the same engineUrl & config.

containsKeyspace

public boolean containsKeyspace(ai.grakn.Keyspace keyspace)

Checks if the keyspace exists in the system. The persisted graph is checked each time because the graph may have been deleted in another JVM.

Parameters:

keyspace - The Keyspace which might be in the system

Returns:

true if the keyspace is in the system

deleteKeyspace

public boolean deleteKeyspace(ai.grakn.Keyspace keyspace)

This is called when a graph is deleted via GraknAdmin.delete(). This removes the keyspace of the deleted graph from the system graph

Parameters:

keyspace - the Keyspace to be removed from the system graph

loadSystemSchema

public void loadSystemSchema()

Load the system schema into a newly created system keyspace. Because the schema only consists of types, the inserts are idempotent and it is safe to load it multiple times.