TableCellCache.old.cs

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// 
//  Copyright 2010-2015 Deveel
// 
//    Licensed 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.
//

using System;

using Deveel.Data.DbSystem;

namespace Deveel.Data.Caching {
    public sealed class TableCellCache {
        private Cache cache;
        private long size;

        public const int DefaultHashSize = 88547;

        public TableCellCache(IDatabaseContext context, ICache baseCase, int maxSize, int maxCellSize) 
            : this(context, baseCase, maxSize, maxCellSize, DefaultHashSize) {
        }

        public TableCellCache(IDatabaseContext context, ICache baseCase, int maxSize, int maxCellSize, int hashSize) {
            Context = context;
            MaxCellSize = maxCellSize;

            cache = new Cache(this, baseCase, hashSize, maxSize);
        }

        public long Size {
            get {
                lock (this) {
                    return size;
                }
            }
        }

        public int MaxCellSize { get; private set; }

        public IDatabaseContext Context { get; private set; }

        private void ReduceCacheSize(long value) {
            size -= value;
        }

        public void Clear() {
            lock (this) {
                if (cache.NodeCount == 0 && Size != 0) {
                    // TODO: Raise an error
                }
                if (cache.NodeCount != 0) {
                    cache.Clear();
                    // TODO: Register the statistics
                }

                size = 0;
            }
        }

        public void AlterCacheDynamics(int maxCacheSize, int maxCellSize) {
            lock (this) {
                MaxCellSize = maxCellSize;
                cache.ChangeSize(maxCacheSize);
            }
        }

        public void Set(int tableKey, int row, int column, DataObject value) {
            if (!value.IsCacheable)
                throw new ArgumentException(String.Format("A value of type '{0}' cannot be stored in cache.", value.Type));

            lock (this) {
                int memoryUse = AmountMemory(value);
                if (memoryUse <= MaxCellSize) {
                    // Generate the key
                    var key = new CacheKey(tableKey, row, (short)column);

                    // If there is an existing object here, remove it from the cache and
                    // update the current_cache_size.
                    var removedCell = (DataObject) cache.Remove(key);
                    if (!Equals(removedCell,  null)) {
                        size -= AmountMemory(removedCell);
                    }

                    // Put the new entry in the cache
                    cache.Set(key, value);
                    size += memoryUse;
                } else {
                    // If the object is larger than the minimum object size that can be
                    // cached, remove any existing entry (possibly smaller) from the cache.
                    Remove(tableKey, row, column);
                }
            }
        }

        private static int AmountMemory(DataObject value) {
            return 16 + value.CacheUsage;
        }

        public DataObject Get(int tableKey, int row, int column) {
            lock (this) {
                return (DataObject)cache.Get(new CacheKey(tableKey, row, (short)column));
            }
        }

        public DataObject Remove(int tableKey, int row, int column) {
            lock (this) {
                var cell = (DataObject)cache.Remove(new CacheKey(tableKey, row, (short)column));
                if (cell != null)
                    size -= AmountMemory(cell);

                return cell;
            }
        }

        #region Cache

        class Cache : CacheAdapter {
            private readonly TableCellCache tableCache;
            private int hashSize;

            public Cache(TableCellCache tableCache, ICache baseCache, int hashSize, int maxSize) 
                : base(baseCache, maxSize) {
                this.tableCache = tableCache;
                this.hashSize = hashSize;
            }

            public void ChangeSize(int newSize) {
                hashSize = newSize;
                CheckClean();
            }

            protected override void CheckClean() {
                if (tableCache.Size >= hashSize) {
                    // TODO: Register the statistics

                    Clean();

                    //TODO: Register the statistics
                }
            }

            protected override bool WipeMoreNodes() {
                return (tableCache.Size >= (int)((hashSize * 100L) / 115L));
            }

            protected override void OnWipingNode(object ob) {
                base.OnWipingNode(ob);

                // Update our memory indicator accordingly.
                var value = (DataObject)ob;
                tableCache.ReduceCacheSize(AmountMemory(value));
            }

            protected override void OnGetWalks(long totalWalks, long totalGetOps) {
                // TODO: Register the statistics ...
                base.OnGetWalks(totalWalks, totalGetOps);
            }
        }

        #endregion

        #region CacheKey

        class CacheKey : IEquatable<CacheKey> {
            private readonly short column;
            private readonly int row;
            private readonly int tableId;

            public CacheKey(int tableId, int row, short column) {
                this.tableId = tableId;
                this.row = row;
                this.column = column;
            }

            public override bool Equals(object obj) {
                return Equals((CacheKey) obj);
            }

            public override int GetHashCode() {
                // Yicks - this one is the best by far!
                return (((int)column + tableId + (row * 189977)) * 50021) << 4;
            }

            public bool Equals(CacheKey other) {
                return row == other.row &&
                       column == other.column &&
                       tableId == other.tableId;
            }
        }

        #endregion
    }
}