#include <userver/storages/mongo/pool.hpp>

Detailed Description

MongoDB client pool.

Use constructor only for tests, in production the pool should be retrieved from the components via components::Mongo::GetPool() or components::MultiMongo::GetPool().

Example usage:

inline void SampleMongoPool(storages::mongo::Pool& pool) {
    using formats::bson::MakeArray;
    using formats::bson::MakeDoc;
 
    auto in_coll = pool.GetCollection("aggregate_in");
 
    in_coll.InsertMany({
        formats::bson::MakeDoc("_id", 1, "x", 0),
        formats::bson::MakeDoc("_id", 2, "x", 1),
        formats::bson::MakeDoc("_id", 3, "x", 2),
    });
 
    auto cursor = in_coll.Aggregate(
        MakeArray(
            MakeDoc(storages::mongo::operators::kMatch, MakeDoc("_id", MakeDoc(storages::mongo::operators::kGte, 2))),
            MakeDoc(storages::mongo::operators::kAddFields, MakeDoc("check", true)),
            MakeDoc(storages::mongo::operators::kOut, "aggregate_out")
        ),
        storages::mongo::options::ReadPreference::kSecondaryPreferred,
        storages::mongo::options::WriteConcern::kMajority
    );
    EXPECT_FALSE(cursor);
 
    auto out_coll = pool.GetCollection("aggregate_out");
    EXPECT_EQ(2, out_coll.CountApprox());
    for (const auto& doc : out_coll.Find({})) {
        EXPECT_EQ(doc["_id"].As<int>(), doc["x"].As<int>() + 1);
        EXPECT_TRUE(doc["check"].As<bool>());
    }
}

Definition at line 40 of file pool.hpp.

Public Member Functions
	Pool (Pool &&) noexcept
Pool &	operator= (Pool &&) noexcept
bool	HasCollection (utils::zstring_view name) const
	Checks whether a collection exists.
Collection	GetCollection (std::string name) const
	Returns a handle for the specified collection.
void	DropDatabase ()
std::vector< std::string >	ListCollectionNames () const
	Get a list of all the collection names in the associated database.
void	Ping ()
Transaction	BeginTransaction () const
	Begin a new transaction.
template<typename... Options>
Cursor	Aggregate (formats::bson::Value pipeline, Options &&... options)
	Executes an aggregation pipeline on the database, without a collection.
Prepared operation executors
Cursor	Execute (const operations::Aggregate &)

Member Function Documentation

◆ Aggregate()

template<typename... Options>

Cursor storages::mongo::Pool::Aggregate	(	formats::bson::Value	pipeline,
		Options &&...	options )

Executes an aggregation pipeline on the database, without a collection.

Parameters

pipeline	an array of aggregation operations
options	see storages::mongo::options

Corresponds to MongoDB db.aggregate([...]). Use this for pipelines that cannot run on a collection, for example when the first stage is $documents.

On sharded clusters MongoDB may reject $documents together with $lookup: $documents must run on mongos, while $lookup must run on a shard.

See also: Collection::Aggregate
auto cursor =

pool.Aggregate(MakeArray(MakeDoc(mongo::operators::kDocuments, MakeArray(MakeDoc("x", 1), MakeDoc("x", 2)))));

std::vector<int> values;

for (const auto& doc : cursor) {

values.push_back(doc["x"].As<int>());

}

Definition at line 115 of file pool.hpp.

◆ BeginTransaction()

Transaction storages::mongo::Pool::BeginTransaction ( ) const

Begin a new transaction.

Returns: Transaction handle for executing operations within transaction context

Exceptions

MongoException if transaction cannot be started

◆ DropDatabase()

void storages::mongo::Pool::DropDatabase ( )

Drops the associated database if it exists. New modifications of collections will attempt to re-create the database automatically.

◆ Ping()

void storages::mongo::Pool::Ping ( )