ClickHouse/src/Storages/StorageFactory.h

#pragma once

#include <Common/NamePrompter.h>
#include <Databases/LoadingStrictnessLevel.h>
#include <Parsers/IAST_fwd.h>
#include <Parsers/ASTCreateQuery.h>
#include <Storages/ColumnsDescription.h>
#include <Storages/ConstraintsDescription.h>
#include <Storages/IStorage_fwd.h>
#include <Storages/registerStorages.h>
#include <Access/Common/AccessType.h>
#include <unordered_map>


namespace DB
{

class Context;
struct StorageID;


/** Allows to create a table by the name and parameters of the engine.
  * In 'columns' Nested data structures must be flattened.
  * You should subsequently call IStorage::startup method to work with table.
  */
class StorageFactory : private boost::noncopyable, public IHints<>
{
public:

    static StorageFactory & instance();

    struct Arguments
    {
        const String & engine_name;
        /// Mutable to allow replacing constant expressions with literals, and other transformations.
        ASTs & engine_args;
        ASTStorage * storage_def;
        const ASTCreateQuery & query;
        /// Path to table data.
        /// Relative to <path> from server config (possibly <path> of some <disk> of some <volume> for *MergeTree)
        const String & relative_data_path;
        const StorageID & table_id;
        ContextWeakMutablePtr local_context;
        ContextWeakMutablePtr context;
        const ColumnsDescription & columns;
        const ConstraintsDescription & constraints;
        LoadingStrictnessLevel mode;
        const String & comment;

        ContextMutablePtr getContext() const;
        ContextMutablePtr getLocalContext() const;
    };

    /// Analog of the IStorage::supports*() helpers
    /// (But the former cannot be replaced with StorageFeatures due to nesting)
    struct StorageFeatures
    {
        bool supports_settings = false;
        bool supports_skipping_indices = false;
        bool supports_projections = false;
        bool supports_sort_order = false;
        /// See also IStorage::supportsTTL()
        bool supports_ttl = false;
        /// See also IStorage::supportsReplication()
        bool supports_replication = false;
        /// See also IStorage::supportsDeduplication()
        bool supports_deduplication = false;
        /// See also IStorage::supportsParallelInsert()
        bool supports_parallel_insert = false;
        bool supports_schema_inference = false;
        AccessType source_access_type = AccessType::NONE;
    };

    using CreatorFn = std::function<StoragePtr(const Arguments & arguments)>;
    struct Creator
    {
        CreatorFn creator_fn;
        StorageFeatures features;
    };

    using Storages = std::unordered_map<std::string, Creator>;

    StoragePtr get(
        const ASTCreateQuery & query,
        const String & relative_data_path,
        ContextMutablePtr local_context,
        ContextMutablePtr context,
        const ColumnsDescription & columns,
        const ConstraintsDescription & constraints,
        LoadingStrictnessLevel mode) const;

    /// Register a table engine by its name.
    /// No locking, you must register all engines before usage of get.
    void registerStorage(const std::string & name, CreatorFn creator_fn, StorageFeatures features = StorageFeatures{
        .supports_settings = false,
        .supports_skipping_indices = false,
        .supports_projections = false,
        .supports_sort_order = false,
        .supports_ttl = false,
        .supports_replication = false,
        .supports_deduplication = false,
        .supports_parallel_insert = false,
        .supports_schema_inference = false,
        .source_access_type = AccessType::NONE,
    });

    const Storages & getAllStorages() const
    {
        return storages;
    }

    std::vector<String> getAllRegisteredNames() const override
    {
        std::vector<String> result;
        auto getter = [](const auto & pair) { return pair.first; };
        std::transform(storages.begin(), storages.end(), std::back_inserter(result), getter);
        return result;
    }

    using FeatureMatcherFn = std::function<bool(StorageFeatures)>;
    std::vector<String> getAllRegisteredNamesByFeatureMatcherFn(FeatureMatcherFn feature_matcher_fn) const
    {
        std::vector<String> result;
        for (const auto& pair : storages)
            if (feature_matcher_fn(pair.second.features))
                result.push_back(pair.first);
        return result;
    }

    AccessType getSourceAccessType(const String & table_engine) const;

    const StorageFeatures & getStorageFeatures(const String & storage_name) const;

private:
    Storages storages;
};

}