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From "Joel Bernstein (JIRA)" <>
Subject [jira] [Commented] (SOLR-8888) Add shortestPath Streaming Expression
Date Tue, 29 Mar 2016 14:53:25 GMT


Joel Bernstein commented on SOLR-8888:

I was suggesting that we can have both a generic approach to graph traversals (like the ReducerStream)
and specific graph expressions. Eventually the generic approach could power the specific expression.

In the beginning it's easier to start with a couple of specific uses cases to iron out the
mechanics of how to do the distributed traversals. This will help us come up with a generic

> Add shortestPath Streaming Expression
> -------------------------------------
>                 Key: SOLR-8888
>                 URL:
>             Project: Solr
>          Issue Type: Improvement
>            Reporter: Joel Bernstein
>         Attachments: SOLR-8888.patch, SOLR-8888.patch, SOLR-8888.patch, SOLR-8888.patch
> This ticket is to implement a distributed shortest path graph traversal as a Streaming
> Expression syntax:
> {code}
> shortestPath(collection, 
>                      from="node1", 
>                      to="node2",
>                      edge="colA=colB",
>                      threads="6",
>                      partitionSize="300", 
>                      fq="limiting query", 
>                      maxDepth="4")
> {code}
> The expression above performs a *breadth first search* to find the shortest path in an
unweighted, directed graph. The search is performed  *from* node1 *to* node2, traversing the
*edge* *joining* colA to colB iteratively. Each level in the traversal is implemented as a
*parallel partitioned* nested loop join across the entire *collection*. The *threads* parameter
controls the number of threads performing the join at each level. The *partitionSize* controls
the of number of nodes in each join partition. *maxDepth* controls the number of levels to
traverse. *fq* is a limiting query applied to each level in the traversal.
> Future implementations can add more capabilities such as weighted traversals.

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