Decided to play with some syntax a bit just to see where this might go.
Here is the original:
gremlin> g.withStrategies(ReadOnlyStrategy.instance()).V().addE('knows')
The provided traversal has a mutating step and thus is not read only:
AddEdgeStep({label=[knows]})
Type ':help' or ':h' for help.
Display stack trace? [yN]n
gremlin> g =
g.withStrategies(SubgraphStrategy.build().vertexProperties(hasNot('endTime')).create())
//2\
==>graphtraversalsource[tinkergraph[vertices:6 edges:14], standard]
gremlin> g.V().as('a').values('location').as('b'). //3\
select('a','b').by('name').by()
==>[a:marko,b:santa fe]
==>[a:stephen,b:purcellville]
==>[a:matthias,b:seattle]
==>[a:daniel,b:aachen]
Here is the revision:
gremlin> g.withStrategy(ReadOnlyStrategy).V().addE('knows')
The provided traversal has a mutating step and thus is not read only:
AddEdgeStep({label=[knows]})
Type ':help' or ':h' for help.
Display stack trace? [yN]n
gremlin> g = g.withStrategy(SubgraphStrategy, [vertexProperties:
hasNot('endTime')])
==>graphtraversalsource[tinkergraph[vertices:6 edges:14], standard]
gremlin> g.V().as('a').values('location').as('b'). //3\
......1> select('a','b').by('name').by()
==>[a:marko,b:santa fe]
==>[a:stephen,b:purcellville]
==>[a:matthias,b:seattle]
==>[a:daniel,b:aachen]
There is no tricky Groovy stuff going on here - I actually modified Gremlin
in java to have:
TraversalSource withStrategy(Class<? extends TraversalStrategy>
traversalStrategy)
TraversalSource withStrategy(Class<? extends TraversalStrategy>
traversalStrategy,
Map<String, Object> configuration)
While there is something nice about the Builder pattern in Java, I think
the chief issue is that it bloats the Gremlin language with more official
syntax related to strategy construction. If we fall back to a more general
Map configuration approach we lose some type safety and code auto-complete
in Java but I think adding strategies is not a part of the daily work of
Gremlin. It's a special configuration to the TraversalSource, so if we had
to sacrifice a bit there I think we gain a lot more in language consistency.
On Fri, Oct 30, 2020 at 3:08 PM Stephen Mallette <[email protected]>
wrote:
> I've been thinking a bit about TraversalStrategy declarations. There are
> really two forms:
>
> 1. an easy no configuration option which is typically a singleton and is
> just created by instance() like ReadOnlyStrategy.instance()
> 2. a more complex option that uses builder pattern to construct the
> traversal with build()...create() as in
> ReservedKeysVerificationStrategy.build().reservedKeys(new
> HashSet<String>(){{ add("id");}})
>
> The Builder pattern is kinda neat in that it's quite explicit API and
> looks familiar in Java. It doesn't really translate though to other
> languages so well, aside from C# perhaps. We've already gone to
> constructors with named arguments in other languages like Python and
> Javascript which is much more succinct. That leaves Groovy a bit on its own
> and while Groovy could probably follow the Java path it doesn't look quite
> right in practice (which means it doesn't really follow the premise of what
> variants are about):
>
> g.withStrategies(ReservedKeysVerificationStrategy.build().reservedKeys(['id']
> as Set).create()).V()
>
> or more groovy-er
>
> g.withStrategies(new
> ReservedKeysVerificationStrategy(reservedKeys:['id'])).V()
>
> I think about these things because I've been looking at Translator
> implementations lately and it is important that they generate the canonical
> form of their variant so that we have shared consistency for what Gremlin
> is in each language.
>
> Finally, consider that Groovy scripts are still a prevalent way of
> shipping Gremlin around. I've often thought they might die out but they
> remain persistent especially with REST APIs and I imagine even TinkerPop 4
> won't be able to dislodge them. If so, Gremlin in Groovy is likely to be
> the canonical string representation of Gremlin.
>
> For more random thoughts see:
>
> https://issues.apache.org/jira/browse/TINKERPOP-2461
>
> Anyone happen to have any thoughts on this matter?
>
