// @tags: [
//     # Cannot implicitly shard accessed collections because of following errmsg: A single
//     # update/delete on a sharded collection must contain an exact match on _id or contain the
//     # shard key.
//     assumes_unsharded_collection,
// ]

/**
 * Tests running explain on a variety of explainable commands (find, update, remove, etc.) when
 * there are multiple plans available. This is a regression test for SERVER-20849 and SERVER-21376.
 */
(function() {
"use strict";
var coll = db.explainMultiPlan;
coll.drop();

// Create indices to ensure there are multiple plans available.
assert.commandWorked(coll.ensureIndex({a: 1, b: 1}));
assert.commandWorked(coll.ensureIndex({a: 1, b: -1}));

// Insert some data to work with.
var bulk = coll.initializeOrderedBulkOp();
var nDocs = 100;
for (var i = 0; i < nDocs; ++i) {
    bulk.insert({a: i, b: nDocs - i});
}
bulk.execute();

// SERVER-20849: The following commands should not crash the server.
assert.doesNotThrow(function() {
    coll.explain("allPlansExecution").update({a: {$gte: 1}}, {$set: {x: 0}});
});

assert.doesNotThrow(function() {
    coll.explain("allPlansExecution").remove({a: {$gte: 1}});
});

assert.doesNotThrow(function() {
    coll.explain("allPlansExecution").findAndModify({query: {a: {$gte: 1}}, remove: true});
});

assert.doesNotThrow(function() {
    coll.explain("allPlansExecution").findAndModify({query: {a: {$gte: 1}}, update: {y: 1}});
});

assert.doesNotThrow(function() {
    coll.explain("allPlansExecution").find({a: {$gte: 1}}).finish();
});

assert.doesNotThrow(function() {
    coll.explain("allPlansExecution").count({a: {$gte: 1}});
});

assert.doesNotThrow(function() {
    coll.explain("allPlansExecution").distinct("a", {a: {$gte: 1}});
});

// SERVER-21376: Make sure the 'rejectedPlans' field is filled in appropriately.
function assertHasRejectedPlans(explainOutput) {
    var queryPlannerOutput = explainOutput.queryPlanner;

    // The 'rejectedPlans' section will be in a different place if passed through a mongos.
    if ("SINGLE_SHARD" == queryPlannerOutput.winningPlan.stage) {
        var shards = queryPlannerOutput.winningPlan.shards;
        shards.forEach(function assertShardHasRejectedPlans(shard) {
            assert.gt(shard.rejectedPlans.length, 0);
        });
    } else {
        assert.gt(queryPlannerOutput.rejectedPlans.length, 0);
    }
}

var res = coll.explain("queryPlanner").find({a: {$gte: 1}}).finish();
assert.commandWorked(res);
assertHasRejectedPlans(res);

res = coll.explain("executionStats").find({a: {$gte: 1}}).finish();
assert.commandWorked(res);
assertHasRejectedPlans(res);
}());