jstests/core/distinct_compound_index.js


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(function() {
    "use strict";

    load("jstests/libs/analyze_plan.js");

    var coll = db.distinct_multikey_index;

    coll.drop();
    for (var i = 0; i < 10; i++) {
        assert.writeOK(coll.save({a: 1, b: 1}));
        assert.writeOK(coll.save({a: 1, b: 2}));
        assert.writeOK(coll.save({a: 2, b: 1}));
        assert.writeOK(coll.save({a: 2, b: 3}));
    }
    coll.createIndex({a: 1, b: 1});

    var explain_distinct_with_query = coll.explain("executionStats").distinct('b', {a: 1});
    assert.commandWorked(explain_distinct_with_query);
    assert(planHasStage(explain_distinct_with_query.queryPlanner.winningPlan, "DISTINCT_SCAN"));
    assert(planHasStage(explain_distinct_with_query.queryPlanner.winningPlan, "PROJECTION"));
    assert.eq(2, explain_distinct_with_query.executionStats.nReturned);

    var explain_distinct_without_query = coll.explain("executionStats").distinct('b');
    assert.commandWorked(explain_distinct_without_query);
    assert(planHasStage(explain_distinct_without_query.queryPlanner.winningPlan, "COLLSCAN"));
    assert(!planHasStage(explain_distinct_without_query.queryPlanner.winningPlan, "DISTINCT_SCAN"));
    assert.eq(40, explain_distinct_without_query.executionStats.nReturned);
})();