5 replies

Use of by()

Can somebody explain the usecase of by() function in gremlin in very simple language.

Solution

by()

by()

is a step modulator, meaning it modifies the step it is being applied to in some way by giving it some additional instruction. an easy example to see this with is

groupCount()

groupCount()

gremlin> g.V().groupCount()
==>[v[1]:1,v[2]:1,v[3]:1,v[4]:1,v[5]:1,v[6]:1]

gremlin> g.V().groupCount()
==>[v[1]:1,v[2]:1,v[3]:1,v[4]:1,v[5]:1,v[6]:1]

Calling

groupCount()

groupCount()

without modulation implies the default behavior of grouping on the incoming traverser (i.e. the current

Vertex

Vertex

). Each

Vertex

Vertex

is simply counted once as a result as they are each unique entities. If we want to change that grouping behavior, we modulate that step with

by()

by()

, like:

gremlin> g.V().groupCount().by(label)
==>[software:2,person:4]

gremlin> g.V().groupCount().by(label)
==>[software:2,person:4]

Now we're saying, go ahead and group count the vertices but use the label of the

Vertex

Vertex

for the grouping. it is important to note that what

by()

by()

does is dependent on the step to which it is applied (and that on its own it really doesn't do anything at all).

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Apache TinkerPop•3y ago•

5 replies

Faraz

Use of by()

Can somebody explain the usecase of by() function in gremlin in very simple language.

Solution

by()

by()

is a step modulator, meaning it modifies the step it is being applied to in some way by giving it some additional instruction. an easy example to see this with is

groupCount()

groupCount()

gremlin> g.V().groupCount()
==>[v[1]:1,v[2]:1,v[3]:1,v[4]:1,v[5]:1,v[6]:1]

gremlin> g.V().groupCount()
==>[v[1]:1,v[2]:1,v[3]:1,v[4]:1,v[5]:1,v[6]:1]

Calling

groupCount()

groupCount()

without modulation implies the default behavior of grouping on the incoming traverser (i.e. the current

Vertex

Vertex

). Each

Vertex

Vertex

is simply counted once as a result as they are each unique entities. If we want to change that grouping behavior, we modulate that step with

by()

by()

, like:

gremlin> g.V().groupCount().by(label)
==>[software:2,person:4]

gremlin> g.V().groupCount().by(label)
==>[software:2,person:4]

Now we're saying, go ahead and group count the vertices but use the label of the

Vertex

Vertex

for the grouping. it is important to note that what

by()

by()

does is dependent on the step to which it is applied (and that on its own it really doesn't do anything at all).

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Use of by()

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