How does Edge Index differ from Relation Index in janusGraph or are they the same?-CodePudding

I am quite new to janusgraph and I am in the process of indexing my graph.

Through the process I have discovered that we could index the edges like we index vertices.

FYI : I am indexing vertices using mixed - elastic search

This is the script that I have followed from the documentation

graph.tx().rollback()
mgmt = graph.openManagement()
type = mgmt.getPropertyKey('type')
has_reported = mgmt.getEdgeLabel('has_reported')
mgmt.buildEdgeIndex(has_reported, 'reportedByType', Direction.BOTH, Order.desc, type)
mgmt.commit()
ManagementSystem.awaitRelationIndexStatus(graph, 'reportedByType', 'has_reported').call()
mgmt = graph.openManagement()
mgmt.updateIndex(mgmt.getRelationIndex(has_reported, "reportedByType"), SchemaAction.REINDEX).get()
mgmt.commit()

From the above script, here I have an edge 'has_reported' containing a property 'type'. After excuting the above script I had my edge 'REGISTERED' and successfully reindex with final status 'ENABLED' as below.

gremlin> mgmt.printIndexes()
==>------------------------------------------------------------------------------------------------
Vertex Index Name              | Type        | Unique    | Backing        | Key:           Status |
---------------------------------------------------------------------------------------------------
byUserNameMixed                | Mixed       | false     | search         | username:     ENABLED |
byPasswordMixed                | Mixed       | false     | search         | password:     ENABLED |
byStatusIdComposite            | Composite   | false     | internalindex  | status_id:    ENABLED |
---------------------------------------------------------------------------------------------------
Edge Index (VCI) Name          | Type        | Unique    | Backing        | Key:           Status |
---------------------------------------------------------------------------------------------------
---------------------------------------------------------------------------------------------------
Relation Index                 | Type        | Direction | Sort Key       | Order    |     Status |
---------------------------------------------------------------------------------------------------
reportedByType                 | has_reported | BOTH      | type           | desc     |    ENABLED |
---------------------------------------------------------------------------------------------------

Here I have confusion as I see three type of indexes shown

Vertex Index Name
Edge Index (VCI ) Name
Relation Index

Need help on the following

difference between Edge Index (VCI) Name and Relation Index
how to index using 'Edge Index (VCI) Name' as I don't see that in the documentation

Documention referred : https://docs.janusgraph.org/schema/index-management/index-performance/#vertex-centric-indexes

Thanks!

CodePudding user response：

Edited (because the previous answer was not correct for more recent versions of JanusGraph):

I tend to agree that the naming of the JanusGraph indices used to be confusing (as in your question). In JanusGraph 0.6.2 the output of printIndexes() looks different:

gremlin> mgmt.printIndexes()
==>------------------------------------------------------------------------------------------------
Graph Index (Vertex)           | Type        | Unique    | Backing        | Key:           Status |
---------------------------------------------------------------------------------------------------
name                           | Composite   | true      | internalindex  | name:         ENABLED |
vertices                       | Mixed       | false     | search         | age:          ENABLED |
byTestVal                      | Composite   | false     | internalindex  | testval:      ENABLED |
someName                       | Mixed       | false     | search         | p:            ENABLED |
                               |             |           |                | q:            ENABLED |
---------------------------------------------------------------------------------------------------
Graph Index (Edge)             | Type        | Unique    | Backing        | Key:           Status |
---------------------------------------------------------------------------------------------------
edges                          | Mixed       | false     | search         | reason:       ENABLED |
                               |             |           |                | place:        ENABLED |
---------------------------------------------------------------------------------------------------
Relation Index (VCI)           | Type        | Direction | Sort Key       | Order    |     Status |
---------------------------------------------------------------------------------------------------
battlesByTime                  | battled     | BOTH      | time           | desc     |    ENABLED |
---------------------------------------------------------------------------------------------------

The Graph Index (Edge) enables a lookup among all edges in the graph database that have the label and key(s) needed for that relation index. This index is typically triggered with a query g.E().has(key, value).

A Relation Index (VCI-vertex centric index) enables a lookup among the matching edges bound to a single vertex. This index can only be triggered when first traversing to the associated vertex, like g.V().has(keyV, valueV).bothE(labelE).has(keyE, valueE). The vertex centric index enable you to traverse so-called supernodes that have very many connections.

You want the Graph Index (Edge), so you need to instantiate an index builder for that:

mgmt.buildIndex('reportedByType', Edge.class)

see the reference docs for further build steps.