Implicit edge generation can create self-edge

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    • Type: Bug
    • Resolution: Duplicate
    • Priority: Major - P3
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    • Affects Version/s: None
    • Component/s: None
    • Query Optimization
    • ALL
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      /**
 * Reproduces a join optimizer tassert where implicit edge discovery infers an edge from a node to
 * itself after two local fields are equated to the same foreign field.
 *
 * @tags: [
 *   requires_fcv_90,
 *   requires_sbe,
 * ]
 */

TestData.cleanUpCoreDumpsFromExpectedCrash = true;
const conn = MongoRunner.runMongod({
    useLogFiles: false,
    setParameter: {
        featureFlagPathArrayness: true,
        internalEnableJoinOptimization: true,
        internalJoinReorderMode: "bottomUp",
    },
});
assert(conn);
const db = conn.getDB(jsTestName());
const base = db.base;
const foreign = db.foreign;
assert.commandWorked(base.insert({x: 1, z: 1}));
assert.commandWorked(foreign.insert({y: 1}));
assert.commandWorked(base.createIndexes([{x: 1}, {z: 1}]));
assert.commandWorked(foreign.createIndex({y: 1}));

// WILL FAIL: 11180001 "Self edges are not permitted"
assert.commandWorked(
    db.runCommand({
        aggregate: base.getName(),
        pipeline: [
            {
                $lookup: {
                    from: foreign.getName(),
                    let: {lx: "$x", lz: "$z"},
                    pipeline: [
                        {
                            $match: {
                                $expr: {
                                    $and: [{$eq: ["$y", "$$lx"]}, {$eq: ["$y", "$$lz"]}],
                                },
                            },
                        },
                    ],
                    as: "joined",
                },
            },
            {$unwind: "$joined"},
        ],
        cursor: {},
    }),
);

MongoRunner.stopMongod(conn, null, {allowedExitCode: MongoRunner.EXIT_ABORT});
      Show
      /**  * Reproduces a join optimizer tassert where implicit edge discovery infers an edge from a node to  * itself after two local fields are equated to the same foreign field.  *  * @tags: [  *   requires_fcv_90,  *   requires_sbe,  * ]  */ TestData.cleanUpCoreDumpsFromExpectedCrash = true ; const conn = MongoRunner.runMongod({     useLogFiles: false ,     setParameter: {         featureFlagPathArrayness: true ,         internalEnableJoinOptimization: true ,         internalJoinReorderMode: "bottomUp" ,     }, }); assert (conn); const db = conn.getDB(jsTestName()); const base = db.base; const foreign = db.foreign; assert .commandWorked(base.insert({x: 1, z: 1})); assert .commandWorked(foreign.insert({y: 1})); assert .commandWorked(base.createIndexes([{x: 1}, {z: 1}])); assert .commandWorked(foreign.createIndex({y: 1})); // WILL FAIL: 11180001 "Self edges are not permitted" assert .commandWorked(     db.runCommand({         aggregate: base.getName(),         pipeline: [             {                 $lookup: {                     from: foreign.getName(),                     let: {lx: "$x" , lz: "$z" },                     pipeline: [                         {                             $match: {                                 $expr: {                                     $and: [{$eq: [ "$y" , "$$lx" ]}, {$eq: [ "$y" , "$$lz" ]}],                                 },                             },                         },                     ],                     as: "joined" ,                 },             },             {$unwind: "$joined" },         ],         cursor: {},     }), ); MongoRunner.stopMongod(conn, null , {allowedExitCode: MongoRunner.EXIT_ABORT});
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      Implicit-edge generation can create a self-edge, tripping 11180001. addImplicitEdges() unions equal path ids, then blindly adds equality edges between every pair in a DS component. If one lookup has two join predicates equating the same foreign path to two different local paths, the component contains two paths from the same node. MutableJoinGraph::addEdge() then rejects the implied same-node edge.

            Assignee:
            Max Verbinnen
            Reporter:
            Max Verbinnen
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              Created:
              Updated:
              Resolved: