org.janusgraph.graphdb.database.idassigner.placement

Interface IDPlacementStrategy

All Known Implementing Classes:

PropertyPlacementStrategy, SimpleBulkPlacementStrategy

public interface IDPlacementStrategy

Determines how vertices are placed in individual graph partitions. A particular implementation determines the partition id of a (newly created) vertex. The vertex is then assigned to said partition by JanusGraph. The id placement strategy is configurable.

Author:

Matthias Broecheler ([email protected])

Method Summary

Modifier and Type	Method and Description
void	exhaustedPartition(int partitionID) Called when there are no more idAuthorities left in the given partition.
int	getPartition(InternalElement element) Individually assigns an id to the given vertex or relation.
void	getPartitions(Map<InternalVertex,PartitionAssignment> vertices) Bulk assignment of idAuthorities to vertices.
void	injectIDManager(IDManager idManager) After construction, the IDManager used by this graph instance is injected into this IDPlacementStrategy so that the id pattern of vertices can be inspected.
void	setLocalPartitionBounds(List<PartitionIDRange> localPartitionIdRanges) If JanusGraph is embedded, this method is used to indicate to the placement strategy which part of the partition id space is hosted locally so that vertex and edge placements can be made accordingly (i.e.
boolean	supportsBulkPlacement() Whether this placement strategy supports bulk placement.

Method Detail

getPartition

int getPartition(InternalElement element)

Individually assigns an id to the given vertex or relation.

Parameters:

element - Vertex or relation to assign id to.

Returns:

getPartitions

void getPartitions(Map<InternalVertex,PartitionAssignment> vertices)

Bulk assignment of idAuthorities to vertices.

It is expected that the passed in map contains the partition assignment after this method returns. Any initial values in the map are meaningless and to be ignored.

This is an optional operation. Check with supportsBulkPlacement() first.

Parameters:

vertices - Map containing all vertices and their partition placement.

injectIDManager

void injectIDManager(IDManager idManager)

After construction, the IDManager used by this graph instance is injected into this IDPlacementStrategy so that the id pattern of vertices can be inspected. This method is guaranteed to be called before any partition assignments are made.

Parameters:

idManager -

supportsBulkPlacement

boolean supportsBulkPlacement()

Whether this placement strategy supports bulk placement. If not, then getPartitions(java.util.Map) will throw UnsupportedOperationException

Returns:

setLocalPartitionBounds

void setLocalPartitionBounds(List<PartitionIDRange> localPartitionIdRanges)

If JanusGraph is embedded, this method is used to indicate to the placement strategy which part of the partition id space is hosted locally so that vertex and edge placements can be made accordingly (i.e. preferring to assign partitions in the local ranges so that the data is hosted locally which is often faster).

This method can be called at any time while JanusGraph is running. It is typically called right after construction and when the id space is redistributed.

Depending on the storage backend one or multiple ranges of partition ids may be given. However, this list is never empty.

Parameters:

localPartitionIdRanges - List of PartitionIDRanges corresponding to the locally hosted partitions

exhaustedPartition

void exhaustedPartition(int partitionID)

Called when there are no more idAuthorities left in the given partition. It is expected that the placement strategy will no longer use said partition in its placement suggestions.

Parameters:

partitionID - Id of the partition that has been exhausted.