mongodb/jstests/sharding/explain_find_and_modify_sharded.js

/*
 * Test that the explain command supports findAndModify when talking to a mongos
 * and the collection is sharded.
 */
(function() {
    'use strict';

    var collName = 'explain_find_and_modify';

    // Create a cluster with 2 shards.
    var st = new ShardingTest({shards: 2});
    st.stopBalancer();

    var testDB = st.s.getDB('test');
    var shardKey = {a: 1};

    // Create a collection with an index on the intended shard key.
    var shardedColl = testDB.getCollection(collName);
    shardedColl.drop();
    assert.commandWorked(testDB.createCollection(collName));
    assert.commandWorked(shardedColl.ensureIndex(shardKey));

    // Enable sharding on the database and shard the collection.
    // Use "shard0000" as the primary shard.
    assert.commandWorked(testDB.adminCommand({enableSharding: testDB.getName()}));
    var res = testDB.adminCommand({movePrimary: testDB.getName(), to: 'shard0000'});
    assert(res.ok || res.errmsg == "it is already the primary");
    assert.commandWorked(testDB.adminCommand({
        shardCollection: shardedColl.getFullName(),
        key: shardKey
    }));

    // Split and move the chunks so that
    //   chunk { "a" : { "$minKey" : 1 } } -->> { "a" : 10 }                is on shard0000
    //   chunk { "a" : 10 }                -->> { "a" : { "$maxKey" : 1 } } is on shard0001
    assert.commandWorked(testDB.adminCommand({
        split: shardedColl.getFullName(),
        middle: {a: 10}
    }));
    assert.commandWorked(testDB.adminCommand({
        moveChunk: shardedColl.getFullName(),
        find: {a: 10},
        to: 'shard0001'
    }));

    var res;

    // Queries that do not involve the shard key are invalid.
    res = testDB.runCommand({
        explain: {
            findAndModify: collName,
            query: {b: 1},
            remove: true
        },
        verbosity: 'queryPlanner'
    });
    assert.commandFailed(res);

    // Queries that have non-equality queries on the shard key are invalid.
    res = testDB.runCommand({
        explain: {
            findAndModify: collName,
            query: {a: {$gt: 5}},
            update: {$inc: {b: 7}},
        },
        verbosity: 'allPlansExecution'
    });
    assert.commandFailed(res);

    // Asserts that the explain command ran on the specified shard and used the given stage
    // for performing the findAndModify command.
    function assertExplainResult(explainOut, outerKey, innerKey, shardName, expectedStage) {
        assert(explainOut.hasOwnProperty(outerKey));
        assert(explainOut[outerKey].hasOwnProperty(innerKey));

        var shardStage = explainOut[outerKey][innerKey];
        assert.eq('SINGLE_SHARD', shardStage.stage);
        assert.eq(1, shardStage.shards.length);
        assert.eq(shardName, shardStage.shards[0].shardName);
        assert.eq(expectedStage, shardStage.shards[0][innerKey].stage);
    }

    // Test that the explain command is routed to "shard0000" when targeting the lower chunk range.
    res = testDB.runCommand({
        explain: {
            findAndModify: collName,
            query: {a: 0},
            update: {$inc: {b: 7}},
            upsert: true
        },
        verbosity: 'queryPlanner'
    });
    assert.commandWorked(res);
    assertExplainResult(res, 'queryPlanner', 'winningPlan', 'shard0000', 'UPDATE');

    // Test that the explain command is routed to "shard0001" when targeting the higher chunk range.
    res = testDB.runCommand({
        explain: {
            findAndModify: collName,
            query: {a: 20, c: 5},
            remove: true
        },
        verbosity: 'executionStats'
    });
    assert.commandWorked(res);
    assertExplainResult(res, 'executionStats', 'executionStages', 'shard0001', 'DELETE');

})();