Finding the number of edges of a document in ArangoDB

Query

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FOR d, e IN ANY|INBOUND|OUTBOUND documentId edgeCollectionName
  COLLECT AGGREGATE numEdges = LENGTH(1)
  RETURN numEdges

Application: Finding a document with no edge

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FOR doc IN collectionName
  let numEdges = (
    FOR d, e IN ANY|INBOUND|OUTBOUND doc._id edgeCollectionName
      COLLECT AGGREGATE numEdges = LENGTH(1)
      RETURN numEdges
  )[0]
  FILTER numEdges == 0
  RETURN doc