apoc.generate.er fails with IndexOutOfBoundsException

[pecollet]

Expected Behavior (Mandatory)

apoc.generate.er goes through and generates the graph

Actual Behavior (Mandatory)

• nodes are created, but the procedure fails before creating any relationship.
• Neo.ClientError.Procedure.ProcedureCallFailed : "Failed to invoke procedure apoc.generate.er: Caused by: java.lang.IndexOutOfBoundsException: Index -559948134 out of bounds for length 510000"

How to Reproduce the Problem

call apoc.generate.er(510000,750000, 'Node','HAS')

Steps (Mandatory)

1. call cypher above

Screenshots (where it's possibile)

Specifications (Mandatory)

Versions

• OS: macOS
• Neo4j: 4.2.1 (running locally in desktop)
• Neo4j-Apoc:4.2.0.0

[pecollet]

in ErdosRenyiRelationshipGenerator :

protected List<Pair<Integer, Integer>> doGenerateEdges() {
        long threshold = getConfiguration().getNumberOfEdges() * 4;
        long potentialEdges = getConfiguration().getNumberOfNodes() * (getConfiguration().getNumberOfNodes() - 1); 
        if (threshold > potentialEdges) {
            return doGenerateEdgesWithOmitList(); // Make sure to avoid edges
        }

The integer multiplication of numberOfNodes can silently overflow and produce negative values, causing the code to branch into doGenerateEdgesWithOmitList() and then access negative list indexes. => convert to long before multiplying

The bug actually affects calls to the procedure with numberOfNodes such that numberOfNodes * (numberOfNodes-1) overflows as a negative int (and when it overflows positive it may also do unexpected things). So nothing to do with 500000 as my tests made me believe. It can happen for any value over 46341 which is the limit at which the integer multiplication starts overflowing.