options.hpp

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#pragma once
 
/// @file userver/storages/mongo/options.hpp
/// @brief Query options
 
#include <chrono>
#include <cstddef>
#include <cstdint>
#include <initializer_list>
#include <optional>
#include <string>
#include <string_view>
#include <utility>
#include <vector>
 
#include <userver/formats/bson/bson_builder.hpp>
#include <userver/formats/bson/document.hpp>
#include <userver/formats/bson/value.hpp>
 
USERVER_NAMESPACE_BEGIN
 
/// Collection operation options
namespace storages::mongo::options {
 
/// @brief Read preference
/// @see https://github.com/mongodb/mongo-c-driver/blob/master/src/libmongoc/doc/mongoc_read_prefs_t.rst
class ReadPreference {
public:
    enum Mode {
        /// Default mode. All operations read from the current replica set primary.
        kPrimary,
        /// All operations read from among the nearest secondary members of the replica set.
        kSecondary,
        /// In most situations, operations read from the primary but if it is unavailable, operations read from
        /// secondary members.
        kPrimaryPreferred,
        /// In most situations, operations read from among the nearest secondary members, but if no secondaries are
        /// available, operations read from the primary.
        kSecondaryPreferred,
        /// Operations read from among the nearest members of the replica set, irrespective of the member's type.
        kNearest,
    };
 
    explicit ReadPreference(Mode mode);
    ReadPreference(Mode mode, std::vector<formats::bson::Document> tags);
 
    Mode GetMode() const;
    std::optional<std::chrono::seconds> GetMaxStaleness() const;
    const std::vector<formats::bson::Document>& GetTags() const;
 
    /// @brief Sets maximum replication lag for eligible replica.
    /// @note Must be at least 90 seconds, cannot be used with kPrimary mode.
    ReadPreference& SetMaxStaleness(std::optional<std::chrono::seconds> max_staleness);
 
    /// @brief Adds a tag to the tag set.
    /// @note Cannot be used with kPrimary mode.
    ReadPreference& AddTag(formats::bson::Document tag);
 
private:
    Mode mode_;
    std::optional<std::chrono::seconds> max_staleness_;
    std::vector<formats::bson::Document> tags_;
};
 
/// @brief Read concern
/// @see https://docs.mongodb.org/manual/reference/readConcern/
enum class ReadConcern {
    /// no replication checks, default level
    kLocal,
    /// return data replicated to a majority of RS members
    kMajority,
    /// waits for all running majority writes to finish before read
    kLinearizable,
    /// no replication checks, may return orphaned documents if sharded; since 3.6
    kAvailable,
};
 
/// @brief Write concern
/// @see https://docs.mongodb.org/manual/reference/write-concern/
class WriteConcern {
public:
    enum Level {
        /// Wait until propagation to a "majority" of RS nodes
        kMajority,
        /// Do not check for operation errors, do not wait for write, same as `0`
        kUnacknowledged,
    };
 
    /// Default timeout for "majority" write concern
    static constexpr std::chrono::seconds kDefaultMajorityTimeout{1};
 
    /// Creates a write concern with the special level
    explicit WriteConcern(Level level);
 
    /// Creates a write concern waiting for propagation to `nodes_count` RS nodes
    explicit WriteConcern(size_t nodes_count);
 
    /// Creates a write concern defined in RS config
    explicit WriteConcern(std::string tag);
 
    bool IsMajority() const;
    size_t NodesCount() const;
    const std::string& Tag() const;
    std::optional<bool> Journal() const;
    const std::chrono::milliseconds& Timeout() const;
 
    /// Sets write concern timeout, `0` means no timeout
    WriteConcern& SetTimeout(std::chrono::milliseconds timeout);
 
    /// Sets whether to wait for on-disk journal commit
    WriteConcern& SetJournal(bool value);
 
private:
    size_t nodes_count_;
    bool is_majority_;
    std::optional<bool> journal_;
    std::string tag_;
    std::chrono::milliseconds timeout_;
};
 
/// Disables ordering on bulk operations causing them to continue after an error
class Unordered {};
 
/// Enables insertion of a new document when update selector matches nothing
class Upsert {};
 
/// Enables automatic one-time retry of duplicate key errors
class RetryDuplicateKey {};
 
/// Specifies that FindAndModify should return the new version of an object
class ReturnNew {};
 
/// Specifies the number of documents to skip
class Skip {
public:
    explicit Skip(size_t value) : value_(value) {}
 
    size_t Value() const { return value_; }
 
    size_t value_;
};
 
/// @brief Specifies the number of documents to request from the server
/// @note The value of `0` means "no limit".
class Limit {
public:
    explicit Limit(size_t value) : value_(value) {}
 
    size_t Value() const { return value_; }
 
private:
    size_t value_;
};
 
/// @brief Selects fields to be returned
/// @note `_id` field is always included by default, order might be significant
/// @see
/// https://docs.mongodb.com/manual/tutorial/project-fields-from-query-results/
class Projection {
public:
    /// Creates a default projection including all fields
    Projection() = default;
 
    /// Creates a projection including only specified fields
    Projection(std::initializer_list<std::string_view> fields_to_include);
 
    /// Includes a field into the projection
    Projection& Include(std::string_view field);
 
    /// @brief Excludes a field from the projection
    /// @warning Projection cannot have a mix of inclusion and exclusion.
    /// Only the `_id` field can always be excluded.
    Projection& Exclude(std::string_view field);
 
    /// @brief Setups an array slice in the projection
    /// @param field name of the array field to slice
    /// @param limit the number of items to return
    /// @param skip the following number of items
    /// @note `skip` can be negative, this corresponds to counting from the end
    /// backwards.
    /// @note `limit < 0, skip == 0` is equivalent to `limit' = -limit, skip' =
    /// limit`.
    /// @warning Cannot be applied to views.
    Projection& Slice(std::string_view field, int32_t limit, int32_t skip = 0);
 
    /// @brief Matches the first element of an array satisfying a predicate
    /// @param field name of the array to search
    /// @param pred predicate to apply to elements
    /// @note Array field will be absent from the result if no elements match.
    /// @note Empty document as a predicate will only match empty documents.
    Projection& ElemMatch(std::string_view field, const formats::bson::Document& pred);
 
    /// @cond
    /// Projection specification BSON access
    const bson_t* GetProjectionBson() const;
    /// @endcond
 
private:
    formats::bson::impl::BsonBuilder projection_builder_;
};
 
/// Sorts the results
class Sort {
public:
    enum Direction {
        kAscending,
        kDescending,
    };
 
    /// Creates an empty ordering specification
    Sort() = default;
 
    /// Stores the specified ordering specification
    Sort(std::initializer_list<std::pair<std::string_view, Direction>>);
 
    /// Appends a field to the ordering specification
    Sort& By(std::string_view field, Direction direction);
 
    /// @cond
    /// Sort specification BSON access
    const bson_t* GetSortBson() const;
    /// @endcond
 
private:
    formats::bson::impl::BsonBuilder sort_builder_;
};
 
/// @brief Specifies an index to use for the query
/// @warning Only plans using the index will be considered.
class Hint {
public:
    /// Specifies an index by name
    explicit Hint(std::string index_name);
 
    /// Specifies an index by fields covered
    explicit Hint(formats::bson::Document index_spec);
 
    /// @cond
    /// Retrieves a hint value
    const formats::bson::Value& Value() const;
    /// @endcond
 
private:
    formats::bson::Value value_;
};
 
/// @brief Specifies an array of filter documents that
/// determine which array elements to modify for an update
/// operation on an array field.
class ArrayFilters {
public:
    /// Specifies list of filters
    explicit ArrayFilters(std::initializer_list<formats::bson::Document>);
 
    /// @cond
    /// Retrieves an arrayFilters value
    const formats::bson::Value& Value() const;
    /// @endcond
 
private:
    formats::bson::Value value_;
};
 
/// Selects count implementation to use: new aggregation-based or old cmd-based
enum class ForceCountImpl { kAggregate, kCmd };
 
/// Suppresses errors on querying a sharded collection with unavailable shards
class AllowPartialResults {};
 
/// @brief Disables exception throw on server errors, should be checked manually
/// in WriteResult
class SuppressServerExceptions {};
 
/// @brief Enables tailable cursor, which block at the end of capped collections
/// @note Automatically sets `awaitData`.
/// @see https://docs.mongodb.com/manual/core/tailable-cursors/
class Tailable {};
 
/// Sets a comment for the operation, which would be visible in profile data
class Comment {
public:
    explicit Comment(std::string);
 
    const std::string& Value() const;
 
private:
    std::string value_;
};
 
/// @brief Specifies the server-side time limit for the operation
/// @warning This does not set any client-side timeouts.
class MaxServerTime {
public:
    explicit MaxServerTime(const std::chrono::milliseconds& value) : value_(value) {}
 
    const std::chrono::milliseconds& Value() const { return value_; }
 
private:
    std::chrono::milliseconds value_;
};
 
}  // namespace storages::mongo::options
 
USERVER_NAMESPACE_END