// Licensed to the Apache Software Foundation (ASF) under one

// or more contributor license agreements.  See the NOTICE file

// distributed with this work for additional information

// regarding copyright ownership.  The ASF licenses this file

// to you under the Apache License, Version 2.0 (the

// "License"); you may not use this file except in compliance

// with the License.  You may obtain a copy of the License at

//

//   http://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing,

// software distributed under the License is distributed on an

// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY

// KIND, either express or implied.  See the License for the

// specific language governing permissions and limitations

// under the License.

#include <fmt/core.h>

#include <parallel_hashmap/phmap.h>

#include <algorithm>

#include <memory>

#include <mutex>

#include <type_traits>

#include <vector>

#include "common/logging.h"

#include "olap/iterators.h"

#include "olap/olap_common.h"

#include "olap/schema.h"

#include "olap/tablet.h"

#include "olap/tablet_schema.h"

#include "util/time.h"

namespace doris {

namespace segment_v2 {

class Segment;

class SegmentIterator;

using SegmentIteratorUPtr = std::unique_ptr<SegmentIterator>;

} // namespace segment_v2

// The SchemaCache is utilized to cache pre-allocated data structures,

// eliminating the need for frequent allocation and deallocation during usage.

// This caching mechanism proves immensely advantageous, particularly in scenarios

// with high concurrency, where queries are executed simultaneously.

class SchemaCache : public LRUCachePolicyTrackingManual {

public:

    static SchemaCache* instance();

    static void create_global_instance(size_t capacity);

    static std::string get_schema_key(int64_t tablet_id, const std::vector<TColumn>& columns,

                                      int32_t version);

    // Get a shared cached schema from cache, schema_key is a subset of column unique ids

    TabletSchemaSPtr get_schema(const std::string& schema_key) {

        if (!instance() || schema_key.empty()) {

            return {};

        }

        auto* lru_handle = lookup(schema_key);

        if (lru_handle) {

            Defer release([cache = this, lru_handle] { cache->release(lru_handle); });

            auto* value = (CacheValue*)LRUCachePolicy::value(lru_handle);

            VLOG_DEBUG << "use cache schema";

            return value->tablet_schema;

        }

        return {};

    }

    // Insert a shared Schema into cache, schema_key is full column unique ids

    void insert_schema(const std::string& key, TabletSchemaSPtr schema) {

        if (!instance() || key.empty()) {

            return;

        }

        auto* value = new CacheValue;

        value->tablet_schema = schema;

        auto* lru_handle = insert(key, value, 1, schema->mem_size(), CachePriority::NORMAL);

        release(lru_handle);

    }

    class CacheValue : public LRUCacheValueBase {

    public:

        TabletSchemaSPtr tablet_schema = nullptr;

    };

    SchemaCache(size_t capacity)

            : LRUCachePolicyTrackingManual(CachePolicy::CacheType::SCHEMA_CACHE, capacity,

                                           LRUCacheType::NUMBER,

                                           config::schema_cache_sweep_time_sec) {}

private:

    static constexpr char SCHEMA_DELIMITER = '-';

};

} // namespace doris