Query Apache Tinkerpop GraphDB using Gremlin -- Explain the "Drop" "From" "Index" "key" "Label" "Project" "PropertyMap" and "Value" Steps
2020年05月02日
From Step
Index Step
Index each element in the current collection.
Indexing non-collection items results in multiple indexed single-item collections.
Index all software names in their alphabetical order.
Same as statement 1, but with an explicitely specified list indexer.
Index all person names in their alphabetical order and store the result in an ordered map.
Key Step
Takes a Property and extracts the key from it.
Label Step
Takes an Element and extracts its label from it.
Project Step
PropertyMap Step
Yields a Map representation of the properties of an element.
ShortestPath step
Find all shortest paths from marko.
Find all shortest paths to peter.
Find all in-directed paths to josh.
Find all shortest paths from marko to josh.
Find all shortest paths from marko to josh using a custom distance property.
Find all shortest paths from marko to josh and include edges in the result.
TimeLimit Step
Value Step
References
Key Step
Label Step
Project Step
PropertyMap Step
ShortestPath step
Value Step
Drop Step
-
AddEdge Step
AddVertex Step
AddProperty Step
Drop Step
Remove element and properties from the graph. It is a filter step because the traversal yields no outgoing objects.
g.V("5ab8e996-5d52-c7fc-8b63-c53ff975d906").drop().iterate()
g.V().toList()结果:
[v[1], v[2], v[3], v[4], v[5], v[6]]Vertex 5ab8e996-5d52-c7fc-8b63-c53ff975d906 is gone.
From Step
g.V("1").both().as_("person").both().cyclicPath().path().from_("person").toList()结果:
[path[v[2], v[1]], path[v[4], v[1]], path[v[3], v[1]]]
marko = g.V().has('name','marko').next() peter = g.V().has('name','peter').next() g.addE('knows').from_(marko).to(peter).iterate()-
g.V("1").out().toList()结果:
[v[2], v[4], v[6], v[3]]
Index Step
Index each element in the current collection.
g.V().hasLabel("software").toList()结果:
[v[3], v[5]]
Indexing non-collection items results in multiple indexed single-item collections.
g.V().hasLabel("software").index().toList()结果:
[[[v[3], 0]], [[v[5], 0]]]
Index all software names in their alphabetical order.
g.V().hasLabel("software").values("name").fold().order( Scope.local).index().unfold().order().by( __.tail(Scope.local, 1)).toList()结果:
[['lop', 0], ['ripple', 1]]
Same as statement 1, but with an explicitely specified list indexer.
g.V().hasLabel("software").values("name").fold().order( Scope.local).index().with_( WithOptions.indexer, WithOptions.list ).unfold().order().by(__.tail(Scope.local, 1)).toList()结果:
[['lop', 0], ['ripple', 1]]
Index all person names in their alphabetical order and store the result in an ordered map.
g.V().hasLabel("person").values("name").fold().order( Scope.local).index().with_( WithOptions.indexer, WithOptions.map).toList()结果:
[{0: 'josh', 1: 'marko', 2: 'peter', 3: 'vadas'}]
Key Step
Takes a Property and extracts the key from it.
g.V("1").properties().key().toList()结果:
['name', 'age']
Label Step
Takes an Element and extracts its label from it.
g.V().label().toList()结果:
['person', 'person', 'person', 'person', 'software', 'software']
g.V("1").outE().label().toList()结果:
['knows', 'knows', 'created']
g.V("1").properties().label().toList()结果:
['name', 'age']
Project Step
g.V().out('created').project('a','b').by('name').by( __.in_('created').count()).order().by( __.select('b'), Order.decr).select('a').toList()结果:
['lop', 'lop', 'lop', 'ripple']
g.V().has('name','marko').project('out','in').by( __.outE().count()).by( __.inE().count()).toList()结果:
[{'out': 3, 'in': 0}]
PropertyMap Step
Yields a Map representation of the properties of an element.
g.V().propertyMap().toList()结果:
[{'name': [vp[name->marko]], 'age': [vp[age->29]]}, {'name': [vp[name->vadas]], 'age': [vp[age->27]]}, {'name': [vp[name->lop]], 'lang': [vp[lang->java]]}, {'name': [vp[name->josh]], 'age': [vp[age->32]]}, {'name': [vp[name->ripple]], 'lang': [vp[lang->java]]}, {'name': [vp[name->peter]], 'age': [vp[age->35]]}]
g.V().propertyMap('age').toList()结果:
[{'age': [vp[age->29]]}, {'age': [vp[age->27]]}, {}, {}, {'age': [vp[age->32]]}, {'age': [vp[age->35]]}]
g.V().propertyMap('age','blah').toList()结果:
[{'age': [vp[age->29]]}, {'age': [vp[age->27]]}, {}, {}, {'age': [vp[age->32]]}, {'age': [vp[age->35]]}]
g.E().propertyMap().toList()结果:
[{'weight': p[weight->0.5]}, {'weight': p[weight->1.0]}, {'weight': p[weight->0.4]}, {'weight': p[weight->1.0]}, {'weight': p[weight->0.4]}, {'weight': p[weight->0.2]}]
ShortestPath step
Find all shortest paths from marko.
g = g.withComputer() g.V().shortestPath()结果:
[['withStrategies', VertexProgramStrategy]][['V'], ['shortestPath']]
g.V().has('person','name','marko').shortestPath()结果:
[['withStrategies', VertexProgramStrategy]][['V'], ['has', 'person', 'name', 'marko'], ['shortestPath']]
Find all shortest paths to peter.
Find all in-directed paths to josh.
Find all shortest paths from marko to josh.
Find all shortest paths from marko to josh using a custom distance property.
Find all shortest paths from marko to josh and include edges in the result.
g.V().shortestPath().with(ShortestPath.target, __.has('name','peter')) //3\ g.V().shortestPath(). with(ShortestPath.edges, Direction.IN). with(ShortestPath.target, __.has('name','josh')) //4\ g.V().has('person','name','marko'). shortestPath(). with(ShortestPath.target, __.has('name','josh')) //5\ g.V().has('person','name','marko'). shortestPath(). with(ShortestPath.target, __.has('name','josh')). with(ShortestPath.distance, 'weight') //6\ g.V().has('person','name','marko'). shortestPath(). with(ShortestPath.target, __.has('name','josh')). with(ShortestPath.includeEdges, true) //7 Find all shortest paths.结果:
TimeLimit Step
g.V().repeat( __.both().groupCount('m')).times(16).cap('m').order( Scope.local).by( Column.values, Order.decr).next()结果:
Query cannot be completed due to memory limitations.
Value Step
g.V("1").properties().value().toList()结果:
['marko', 29]
References
Key Step
Label Step
Project Step
PropertyMap Step
ShortestPath step
Value Step
Drop Step