Pipeline pushdown exposes leading $match

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    • Type: Bug
    • Resolution: Unresolved
    • 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 when pipeline pushdown exposes a leading $match after the
 * optimizer has already built the base collection CanonicalQuery.
 *
 * @tags: [
 *   requires_fcv_90,
 *   requires_sbe,
 * ]
 */

TestData.cleanUpCoreDumpsFromExpectedCrash = true;
const conn = MongoRunner.runMongod({
    useLogFiles: true,
    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}));
assert.commandWorked(foreign.insert({y: 1}));
assert.commandWorked(base.createIndex({x: 1}));
assert.commandWorked(foreign.createIndex({y: 1}));

// WILL FAIL: 11116400 "unexpected $match"
assert.commandWorked(
    db.runCommand({
        aggregate: base.getName(),
        pipeline: [
            {$limit: 1},
            {$match: {x: 1}},
            {$lookup: {from: foreign.getName(), localField: "x", foreignField: "y", as: "joined"}},
            {$unwind: "$joined"},
        ],
        cursor: {},
    }),
);

MongoRunner.stopMongod(conn, null, {allowedExitCode: MongoRunner.EXIT_ABRUPT});
      Show
      /**  * Reproduces a join optimizer tassert when pipeline pushdown exposes a leading $match after the  * optimizer has already built the base collection CanonicalQuery.  *  * @tags: [  *   requires_fcv_90,  *   requires_sbe,  * ]  */ TestData.cleanUpCoreDumpsFromExpectedCrash = true ; const conn = MongoRunner.runMongod({     useLogFiles: true ,     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})); assert .commandWorked(foreign.insert({y: 1})); assert .commandWorked(base.createIndex({x: 1})); assert .commandWorked(foreign.createIndex({y: 1})); // WILL FAIL: 11116400 "unexpected $match" assert .commandWorked(     db.runCommand({         aggregate: base.getName(),         pipeline: [             {$limit: 1},             {$match: {x: 1}},             {$lookup: {from: foreign.getName(), localField: "x" , foreignField: "y" , as: "joined" }},             {$unwind: "$joined" },         ],         cursor: {},     }), ); MongoRunner.stopMongod(conn, null , {allowedExitCode: MongoRunner.EXIT_ABRUPT});
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      Leading $match can remain after createCanonicalQuery() pushdown, tripping 11116400. AggJoinModel::constructJoinModel() assumes any $match seen in its join-prefix loop must come after at least one absorbed $lookup. But createCanonicalQuery() can remove a leading $limit/$skip/projection from suffix without re-consuming a newly exposed $match.

            Assignee:
            Unassigned
            Reporter:
            Max Verbinnen
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            Watchers:
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              Created:
              Updated: