Document path representation as multivalued fields: sensible?

[Marc]

Hi there,

I am running an application comprising approx. 20 million documents. To 
make these documents searchable, I decided to give SOLR a try and feed 
meta-information about my documents into SOLR using a Python script. 
This all works fine. My question is there less a technical one, but 
rather a structural/strategic one.

In my document collection, documents can have parent-documents, and in 
particular not only one parent document, but potentially several parent 
documents. Each document is identified uniquely by an ID value. Child 
documents refer to their parents using a multi-value field 'parent' 
which holds the parent's ID values.

I am interested in the paths that lead from leaf-documents (documents 
that only have parents, but no further children) back to the root 
document. My idea was to add any parent document of a child document 
(also those further away than the immediate parents, so grandparent and 
grand-grand-... parent documents) into this multi-value parent property.

Later, I want to be able to pick any document X from my 20 million 
documents and efficiently determine the set of documents of which X is a 
parent. I.e., all documents that have an entry of X's ID somewhere in 
their parent field.

* Is my strategy of structuring my documents by means of the multi-value 
property sensible?
* Does SOLR provide better methods (that I'm not aware of) to achieve 
the same?
* Will this perform properly? Or is my structuring method likely to keel 
over at some stage if the number of documents keeps growing?

Best,
Marc