How to replace deprecated addInE and addOutE steps with addE?

Question

I am completely new to Gremlin and have some really old code that is using addInE() and addOutE(). I understand that it is deprecated as of release 3.1.0 and - according to the javadocs - should be replaced with addE().

My problem is that I have very little knowledge of Gremlin in general and found almost no documentation for the addInE() and addOutE() steps. In the reference documentation for version 3.0.0 there is exactly one example where it is used, but not explained.
Here is the example that is given:

gremlin> g.V(1).as('a').out('created').in('created').where(neq('a')).addOutE('co-developer','a','year',2009) //(1)
==>e[12][4-co-developer->1]
==>e[13][6-co-developer->1]
gremlin> g.withSideEffect('a',g.V(3,5).toList()).V(4).addInE('createdBy','a') //(2)
==>e[14][3-createdBy->4]
==>e[15][5-createdBy->4]
gremlin> g.V().as('a').out('created').as('b').select('a','b').addOutE('b','createdBy','a','acl','public') //(3)
==>e[16][3-createdBy->1]
==>e[17][5-createdBy->4]
==>e[18][3-createdBy->4]
==>e[19][3-createdBy->6]
gremlin> g.V(1).as('a').out('knows').addInE('livesNear','a','year',2009).inV().inE('livesNear').values('year') //(4)
==>2009
==>2009

My current interpretation of the first query

• g.V(1).as('a').out('created').in('created').where(neq('a')) selects elements from the graph
• addOutE('co-developer','a','year',2009) will add something to the selection

I would appreciate if someone could first elaborate on what is happening here and then point out how addInE() and addOutE() could be represented using addE().

Answer 1

This is a trip down memory lane!

Using one of the examples you found

gremlin> g.V(1).as('a').out('created').in('created').where(neq('a')).addOutE('co-developer','a','year',2009)

would, in current day Gremlin be written as

g.V(1).as('a').
       out('created').
       in('created').
       where(neq('a')).
       addE('co-developer').to('a').property('year',2009)

The way to read this is

1. Starting at the vertex with an ID of one.
2. Find all the vertices connected to V(1) by outgoing 'created' edges
3. Find all the people who also created the same thing
4. Don't include where you started (ie ignore yourself)
5. Add a new 'co-developer' edge to V(1) from the people found, with an edge property of the year.

When replacing addInE still use the addE step, but replace the to with a from. Note that an addE can also have both from and to used with it at the same time.