Recently <https://issues.apache.org/jira/browse/TINKERPOP3-753> on the
TinkerPop issue tracker we came to the conclusion that we should get rid of
select() (not select() altogether, but the parameter-less overload). As
select(...) becomes more powerful with every release, the parameter-less
select() also becomes more and more expensive and we think you / the user
should actually know what he/she wants to select, thus specifying the keys
shouldn't be a problem.
Initially I was worried about dynamically created traversals, where several
methods may add a piece to the final traversal. But this still shouldn't be
an issue, since you should know what you want to select in the end anyway.
And even if not, you can keep track of the keys and ultimately do this:
traversal.select(keys as String[]) // in Groovy
traversal.select(keys.toArray(new String[keys.size()])) // in Java
There are a few pitfalls though. For those who don't want to read the posts
in the issue tracker:
gremlin> g.V().match(
gremlin> __.as("v").outE().count().as("outD"),
gremlin> __.as("v").inE().count().as("inD")
gremlin> ).select("v").by(valueMap()).
gremlin> select("name","age","outD","inD")
==>[name:[marko], age:[29], outD:3, inD:0]
==>[name:[vadas], age:[27], outD:0, inD:1]
==>[name:[josh], age:[32], outD:2, inD:1]
==>[name:[peter], age:[35], outD:1, inD:0]
As you can see, we only got the person vertices; software vertices are
missing. That's because software vertices don't have an age property. But
since we know our graph schema very well, we can easily solve it:
gremlin> g.V().match(
gremlin> __.as("v").outE().count().as("outD"),
gremlin> __.as("v").inE().count().as("inD")
gremlin> ).select("v").by(valueMap())*.choose(select("age"),*
gremlin> select("name","age","outD","inD"),
gremlin> *select("name","lang","outD","inD"))*
==>[name:[marko], age:[29], outD:3, inD:0]
==>[name:[vadas], age:[27], outD:0, inD:1]
*==>[name:[lop], lang:[java], outD:0, inD:3]*
==>[name:[josh], age:[32], outD:2, inD:1]
*==>[name:[ripple], lang:[java], outD:0, inD:1]*
==>[name:[peter], age:[35], outD:1, inD:0]
If you still have any objections, please speak them out loud now.
Cheers,
Daniel
