Modelling a filesystem with a GraphDB

[Mark McKeown]

Hi,

    I have some newbie questions - I am looking at modelling parts of a filesystem using a GraphDB. I want to store metadata about parts of the filesystem in the GraphDB.

Is this a good use of GraphDB and Gremlin?

If I want to store information about a path /foo/bar/blah it seems I should have vertices foo, bar and blah and link them together?

How would I query if /foo/bar/blah exists in the GraphDB? I could have another path /soup/cheese/blah for example which would mean a node with the same name?

If I want to add /foo/bar/blah as it does not exist, but /foo/bar does exist how do I query for existing nodes? Can I query and add in the same operation?

Are there any tutorials that provide good examples for this type of case?

cheers

Mark

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[Stephen Mallette]

HI there - some answers inline below:

On Mon, Mar 27, 2023 at 7:28 PM 'Mark McKeown' via Gremlin-users <gremli...@googlegroups.com> wrote:

Hi,

    I have some newbie questions - I am looking at modelling parts of a filesystem using a GraphDB. I want to store metadata about parts of the filesystem in the GraphDB.

Is this a good use of GraphDB and Gremlin?

a file system is a tree and a tree is a graph so the use case fits.  

  

If I want to store information about a path /foo/bar/blah it seems I should have vertices foo, bar and blah and link them together?

yes, that's likely the way to do it.

 

How would I query if /foo/bar/blah exists in the GraphDB? I could have another path /soup/cheese/blah for example which would mean a node with the same name?

"blah" doesn't need to refer to the same vertex. here's the graph you described. you can see in the final query that traverses the little graph that the "blah" vertices are unique with different generated identifiers.

gremlin> g = TinkerGraph.open().traversal()
==>graphtraversalsource[tinkergraph[vertices:0 edges:0], standard]
gremlin> g.addV('directory').property('name','foo').as('v1').
......1>   addV('directory').property('name','bar').as('v2').
......2>   addV('directory').property('name','blah').as('v3').
......3>   addV('directory').property('name','soup').as('v4').
......4>   addV('directory').property('name','cheese').as('v5').
......5>   addV('directory').property('name','blah').as('v6').
......6>   addE('child').from('v1').to('v2').
......7>   addE('child').from('v2').to('v3').
......8>   addE('child').from('v4').to('v5').
......9>   addE('child').from('v5').to('v6').iterate()
gremlin> g.V().has('name','foo').out().out().elementMap()
==>[id:4,label:directory,name:blah]
gremlin> g.V().has('name','soup').out().out().elementMap()
==>[id:10,label:directory,name:blah]

 

If I want to add /foo/bar/blah as it does not exist, but /foo/bar does exist how do I query for existing nodes? Can I query and add in the same operation?

yes, here's a simplified example. it uses coalesce() to check for a path to a vertex with name of "blah" and then adds it if it doesn't exist.

gremlin> g.addV('directory').property('name','foo').as('v1').
......1>   addV('directory').property('name','bar').as('v2').
......2>   addE('child').from('v1').to('v2').iterate()    
gremlin> g.V().has('name','foo').
......1>   out().has('name','bar').as('v1').
......2>   coalesce(out().has('name','blah'),
......3>            addV('directory').property('name','blah').as('v2').
......4>            addE('child').from('v1').to('v2').
......5>            select('v2'))
==>v[5]
gremlin> g.V().has('name','foo').
......1>   out().has('name','bar').as('v1').
......2>   coalesce(out().has('name','blah'),
......3>            addV('directory').property('name','blah').as('v2').
......4>            addE('child').from('v1').to('v2').
......5>            select('v2'))
==>v[5]

 

Are there any tutorials that provide good examples for this type of case?

There is a recipes on trees: https://tinkerpop.apache.org/docs/current/recipes/#tree but i'm not sure what else is out there in this regard. Since you are new, I'd suggest you start learning by reading Kelvin Lawrence's book here:

https://kelvinlawrence.net/book/Gremlin-Graph-Guide.html

and by playing around with Gremlin and your use case in Gremlify:

https://gremlify.com/

 

cheers

Mark

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[Mark McKeown]

Thanks Stephen, this is a great starter for me.

cheers

Mark

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