10 replies

Confusing behavior of `select()`.

The following traversal acts as a counter:

g.withSideEffect("map", [3: "foo", 4: "bar"]).
  inject("a", "b", "c", "d").
  aggregate(local, "x").
  map(select("x").count(local))

g.withSideEffect("map", [3: "foo", 4: "bar"]).
  inject("a", "b", "c", "d").
  aggregate(local, "x").
  map(select("x").count(local))

It produces:

==>1
==>2
==>3
==>4

==>1
==>2
==>3
==>4

I want to modify the traversal to use this count to produce ["foo", "bar"]. So, I tried adding

.as("cnt").select("map").select(select("cnt"))

.as("cnt").select("map").select(select("cnt"))

like this:

g.withSideEffect("map", [3: "foo", 4: "bar"]).
  inject("a", "b", "c", "d").
  aggregate(local, "x").
  map(select("x").count(local)).
  as("cnt").
  select("map").select(select('cnt'))

g.withSideEffect("map", [3: "foo", 4: "bar"]).
  inject("a", "b", "c", "d").
  aggregate(local, "x").
  map(select("x").count(local)).
  as("cnt").
  select("map").select(select('cnt'))

But the code above does not work as expected, it produces no output.

Interestingly, if I change

select("cnt")

select("cnt")

constant(3)

constant(3)

, then it starts producing

foo

foo

==>foo
==>foo
==>foo
==>foo

==>foo
==>foo
==>foo
==>foo

Could someone help me understand why

select("cnt")

select("cnt")

is not working here and why using

constant(3)

constant(3)

works?

Thanks in advance!

Solution

This is caused (if you are using TinkerGraph for example) by Java's HashMap implementation and the fact that a Long will not match an Integer type.

g.withSideEffect("map", [3L: "foo", 4L: "bar"]).
  inject("a", "b", "c", "d").
  aggregate(local, "x").
  map(select("x").count(local)).
  as("cnt").
  select("map").select(select('cnt')) 

==>foo
==>bar

g.withSideEffect("map", [3L: "foo", 4L: "bar"]).
  inject("a", "b", "c", "d").
  aggregate(local, "x").
  map(select("x").count(local)).
  as("cnt").
  select("map").select(select('cnt')) 

==>foo
==>bar

Jump to solution

Apache TinkerPop•17mo ago•

10 replies

Max

Confusing behavior of `select()`.

The following traversal acts as a counter:

g.withSideEffect("map", [3: "foo", 4: "bar"]).
  inject("a", "b", "c", "d").
  aggregate(local, "x").
  map(select("x").count(local))

g.withSideEffect("map", [3: "foo", 4: "bar"]).
  inject("a", "b", "c", "d").
  aggregate(local, "x").
  map(select("x").count(local))

It produces:

==>1
==>2
==>3
==>4

==>1
==>2
==>3
==>4

I want to modify the traversal to use this count to produce ["foo", "bar"]. So, I tried adding

.as("cnt").select("map").select(select("cnt"))

.as("cnt").select("map").select(select("cnt"))

like this:

g.withSideEffect("map", [3: "foo", 4: "bar"]).
  inject("a", "b", "c", "d").
  aggregate(local, "x").
  map(select("x").count(local)).
  as("cnt").
  select("map").select(select('cnt'))

g.withSideEffect("map", [3: "foo", 4: "bar"]).
  inject("a", "b", "c", "d").
  aggregate(local, "x").
  map(select("x").count(local)).
  as("cnt").
  select("map").select(select('cnt'))

But the code above does not work as expected, it produces no output.

Interestingly, if I change

select("cnt")

select("cnt")

constant(3)

constant(3)

, then it starts producing

foo

foo

==>foo
==>foo
==>foo
==>foo

==>foo
==>foo
==>foo
==>foo

Could someone help me understand why

select("cnt")

select("cnt")

is not working here and why using

constant(3)

constant(3)

works?

Thanks in advance!

Solution

This is caused (if you are using TinkerGraph for example) by Java's HashMap implementation and the fact that a Long will not match an Integer type.

g.withSideEffect("map", [3L: "foo", 4L: "bar"]).
  inject("a", "b", "c", "d").
  aggregate(local, "x").
  map(select("x").count(local)).
  as("cnt").
  select("map").select(select('cnt')) 

==>foo
==>bar

g.withSideEffect("map", [3L: "foo", 4L: "bar"]).
  inject("a", "b", "c", "d").
  aggregate(local, "x").
  map(select("x").count(local)).
  as("cnt").
  select("map").select(select('cnt')) 

==>foo
==>bar

Jump to solution

Confusing behavior of `select()`.

Confusing behavior of `select()`.

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