reductionista commented on a change in pull request #486: Graph: Filter out
infinite paths
URL: https://github.com/apache/madlib/pull/486#discussion_r390627982
##########
File path: src/ports/postgres/modules/graph/measures.py_in
##########
@@ -184,10 +184,7 @@ class Graph(object):
-- Filtering 'Infinity' occurs in CASE instead of WHERE clause
-- so that the edge is part of the average value i.e. part of
-- the count of paths but zero addition to sum of distances.
- AVG(CASE WHEN {e.weight} = 'Infinity'::double precision
- THEN 0::double precision
- ELSE {e.weight}::double precision
- END) as avg_path_length
+ AVG({e.weight}::double precision) as avg_path_length
Review comment:
Sounds good to me!
Also backing up this decision, I just noticed this:
```
postgres=# select madlib.graph_avg_path_length();
graph_avg_path_length
-------------------------------------------------------------------------------
This function computes the average of the shortest paths between each pair
of
vertices. Average path length is based on "reachable target vertices", so it
ignores infinite-length paths between vertices that are not connected.
For more details:
SELECT madlib.graph_avg_path_length('usage')
(1 row)
```
Pretty clear the previous behavior was a bug! Glad we've fixed it.
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