mongodb/jstests/core/wildcard_index_hint.js

/**
 * Tests that $** indexes obey hinting.
 */
(function() {
    "use strict";

    load("jstests/aggregation/extras/utils.js");  // For arrayEq.
    load("jstests/libs/analyze_plan.js");         // For getPlanStages.

    const coll = db.wildcard_hint;
    coll.drop();

    const assertArrayEq = (l, r) => assert(arrayEq(l, r), tojson(l) + " != " + tojson(r));

    // Extracts the winning plan for the given query and hint from the explain output.
    const winningPlan = (query, hint) =>
        assert.commandWorked(coll.find(query).hint(hint).explain()).queryPlanner.winningPlan;

    // Runs the given query and confirms that:
    // (1) the expected index was used to answer the query, and
    // (2) the results produced by the index match the given 'expectedResults'.
    function assertExpectedIndexAnswersQueryWithHint(
        query, hint, expectedIndexName, expectedResults) {
        const ixScans = getPlanStages(winningPlan(query, hint), "IXSCAN");
        assert.gt(ixScans.length, 0, tojson(coll.find(query).hint(hint).explain()));
        ixScans.forEach((ixScan) => assert.eq(ixScan.indexName, expectedIndexName));

        const wildcardResults = coll.find(query, {_id: 0}).hint(hint).toArray();
        assertArrayEq(wildcardResults, expectedResults);
    }

    assert.commandWorked(db.createCollection(coll.getName()));

    // Check that error is thrown if the hinted index doesn't exist.
    assert.commandFailedWithCode(
        db.runCommand({find: coll.getName(), filter: {"a": 1}, hint: {"$**": 1}}),
        ErrorCodes.BadValue);

    assert.commandWorked(coll.createIndex({"$**": 1}));

    assert.commandWorked(coll.insert({_id: 10, a: 1, b: 1, c: {d: 1, e: 1}}));
    assert.commandWorked(coll.insert({a: 1, b: 2, c: {d: 2, e: 2}}));
    assert.commandWorked(coll.insert({a: 2, b: 2, c: {d: 1, e: 2}}));
    assert.commandWorked(coll.insert({a: 2, b: 1, c: {d: 2, e: 2}}));
    assert.commandWorked(coll.insert({a: 2, b: 2, c: {e: 2}}));

    // Hint a $** index without a competing index.
    assertExpectedIndexAnswersQueryWithHint(
        {"a": 1},
        {"$**": 1},
        "$**_1",
        [{a: 1, b: 1, c: {d: 1, e: 1}}, {a: 1, b: 2, c: {d: 2, e: 2}}]);

    assert.commandWorked(coll.createIndex({"a": 1}));

    // Hint a $** index with a competing index.
    assertExpectedIndexAnswersQueryWithHint(
        {"a": 1},
        {"$**": 1},
        "$**_1",
        [{a: 1, b: 1, c: {d: 1, e: 1}}, {a: 1, b: 2, c: {d: 2, e: 2}}]);

    // Hint a $** index with a competing _id index.
    assertExpectedIndexAnswersQueryWithHint(
        {"a": 1, "_id": 10}, {"$**": 1}, "$**_1", [{a: 1, b: 1, c: {d: 1, e: 1}}]);

    // Hint a regular index with a competing $** index.
    assertExpectedIndexAnswersQueryWithHint(
        {"a": 1}, {"a": 1}, "a_1", [{a: 1, b: 1, c: {d: 1, e: 1}}, {a: 1, b: 2, c: {d: 2, e: 2}}]);

    // Query on fields that not all documents in the collection have with $** index hint.
    assertExpectedIndexAnswersQueryWithHint(
        {"c.d": 1},
        {"$**": 1},
        "$**_1",
        [{a: 1, b: 1, c: {d: 1, e: 1}}, {a: 2, b: 2, c: {d: 1, e: 2}}]);

    // Adding another wildcard index with a path specified.
    assert.commandWorked(coll.createIndex({"c.$**": 1}));

    // Hint on path that is not in query argument.
    assert.commandFailedWithCode(
        db.runCommand({find: coll.getName(), filter: {"a": 1}, hint: {"c.$**": 1}}),
        ErrorCodes.BadValue);

    // Hint on a path specified $** index.
    assertExpectedIndexAnswersQueryWithHint(
        {"c.d": 1},
        {"c.$**": 1},
        "c.$**_1",
        [{a: 2, b: 2, c: {d: 1, e: 2}}, {a: 1, b: 1, c: {d: 1, e: 1}}]);

    // Min/max with $** index hint.
    assert.commandFailedWithCode(
        db.runCommand({find: coll.getName(), filter: {"b": 1}, min: {"a": 1}, hint: {"$**": 1}}),
        51174);

    // Hint a $** index on a query with compound fields.
    assertExpectedIndexAnswersQueryWithHint(
        {"a": 1, "c.e": 1}, {"$**": 1}, "$**_1", [{a: 1, b: 1, c: {d: 1, e: 1}}]);

    // Hint a $** index by name.
    assertExpectedIndexAnswersQueryWithHint(
        {"a": 1}, "$**_1", "$**_1", [{a: 1, b: 1, c: {d: 1, e: 1}}, {a: 1, b: 2, c: {d: 2, e: 2}}]);
})();