Get the class heirarchy of a vertex

[Chris Whalen]

I have been digging through the java api javadocs as well as the documentation, but I cannot figure out how to get the full class ancestry of a vertex.  I think I can write a separate query against the schema to return the ancestry but it would be best to have it returned in the original query so that I do not have to do multiple queries when working with millions of documents.  I was thinking, something along the lines of:

select @rid, @class, @ancestors from V

Is this possible?

[Chris Whalen]

Has anyone figured out how to return the parent classes of a vertex as a projection?  When I get the vertex, I need to know what it's parent classes are.  So if I get a Square classed vertex, I need to know that it is of a sub class of Rectangle and Shape.

[alessand...@gmail.com]

Hi Chris,

can you send me your schema ?

Alessandro

[Chris Whalen]

Here is the demo schema that I've been playing with.  This is a pretty bare schema.  The inheritance could go much deeper.  With this schema, if I search for BrandAssets, For each entry returned, I need to know that it is a BrandAsset, Asset, and Entity.

[hartmut bischoff]

Hi,

in my view, thats not the job of a database-request. Instead its a matter of your OOP-Design.

I thought, even Java has basic OOP-Support.

So why do you not assign the retrieved Class to the proper Java-Object?

I have done this for ruby. There its just a matter of two lines of code:

    def self.orientdb_class name

       klass = Class.new( self )

       name =  name.to_s.camelize

       if self.send :const_defined?, name

          self.send :const_get, name  # returns the Const

       else

          self.send :const_set  , name , klass  # creates and returns the Const

         end

   end

Elsewhere you simply define the Class in the usual way. Everytime a Database-object is fetched, I call BaseClass.orientdb_class( vertex_name )  and get the proper Ruby-class. 

The ruby-class knows about its parents and has the proper methods to deal with the fetched content.

Take a look at ActiveOrient

Maybe its not that simple in Java, but as Jruby exists, somehow it must work.

[Chris Whalen]

I don't disagree.  Normally, I would not expect a RDB request to return this information but due to orientdb's polymorphism capabilities I think it would be reasonable.  As my schema is not static, I cannot rely on a java object to determine a class' ancestors; new sub classes will be defined during run time.

[hartmut bischoff]

On Friday, July 31, 2015 at 10:20:08 PM UTC+2, Chris Whalen wrote:

I don't disagree.  Normally, I would not expect a RDB request to return this information but due to orientdb's polymorphism capabilities I think it would be reasonable.  As my schema is not static, I cannot rely on a java object to determine a class' ancestors; new sub classes will be defined during run time

For this purpose I maintain a »classes-Object« which is updated whenever a class is created or removed. Then there is a method to get the class-hierarchy of the database, based on the object-root

https://github.com/topofocus/active-orient/blob/master/lib/rest.rb rows 160-220

If you want to go the other way, just define a method 'superClass' for every fetched Object. Then Method.superClass.superClass.(...) reveals the hole tree of the corresponding ruby/java-objects. 

Realisation in Ruby: https://github.com/topofocus/active-orient/blob/master/lib/model.rb rows 56-60

 

[nagaraja sosale ramaswamy]

a possible solution is to write a simple server side function which performs the query against the metadata:schema special target and finds the ancestors. then you could use the function in your sql query, like 'select ancestorClasses(@rid) from #15:2'

such a function itself could be developed using this query gets the immediate ancestor for given @rid:

select superClasses from ( select expand(classes) from metadata:schema ) where name in (select @class from #15:2) unwind superClasses

then you could recurse over the superClasses to obtain the complete hierarchy.

This approach can be easily extended to handle the case of multiple inheritance

[Chris Whalen]

I like this approach. I created a server side function named :GetClassAncestors

var g = orient.getGraphNoTx();

var classLookup = {};

var classSchema = g.command("sql", "select name, superClass from ( select expand(classes) from metadata:schema)");

for(var i=0; i < classSchema.length; i++) {

  

  var schemaClass = classSchema[i];

  var className = schemaClass.getRecord().field('name')

  var parentName = schemaClass.getRecord().field('superClass')

  classLookup[className] = parentName;

  

};

var objectAncestors = [];

var objectAncestor = objectClassName;

while(objectAncestor != null)

{

  objectAncestors[objectAncestors.length] = objectAncestor;

  objectAncestor = classLookup[objectAncestor]

}

return objectAncestors;

You then call it: "select GetClassAncestors(@class) from #15:2"