TableCellCache.cs

Go to the documentation of this file.

// 
//  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.Configuration;

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

        public const int DefaultHashSize = 88547;
#if X64
        public const int DefaultMaxSize = 1024*1024;
#else
        public const int DefaultMaxSize = 512*512;
#endif

        public const int DefaultMaxCellSize = 1024*64;

        public TableCellCache(IConfiguration configuration) {
            Configure(configuration);
        }

        ~TableCellCache() {
            Dispose(false);
        }

        public int MaxCellSize { get; private set; }

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

        public void Dispose() {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        private void Dispose(bool disposing) {
            if (disposing) {
                if (cache != null)
                    cache.Dispose();
            }

            cache = null;
        }

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

        private void Configure(IConfiguration config) {
            var hashSize = DefaultHashSize;
            var maxSize = config.GetInt32("system.tableCellCache.maxSize", DefaultMaxSize);
            MaxCellSize = config.GetInt32("system.tableCellCache.maxCellSize", DefaultMaxCellSize);

            var baseCache = new SizeLimitedCache(maxSize);
            cache = new Cache(this, baseCache, hashSize, maxSize);
        }

        public void Set(CachedCell cell) {
            var value = cell.Value;

            if (!value.IsCacheable)
                return;

            lock (this) {
                int memoryUse = AmountMemory(value);
                if (memoryUse <= MaxCellSize) {
                    // Generate the key
                    var key = new CacheKey(cell.Database, cell.TableId, (int)cell.RowNumber, (short)cell.ColumnOffset);

                    // 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(cell.Database, cell.TableId, cell.RowNumber, cell.ColumnOffset);
                }
            }
        }

        private void Remove(string database, int tableId, long rowNumber, int columnOffset) {
            lock (this) {
                var cell = cache.Remove(new CacheKey(database, tableId, (int)rowNumber, (short)columnOffset));
                if (cell != null)
                    size -= AmountMemory((DataObject) cell);
            }
        }

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

        public bool TryGetValue(CellKey key, out DataObject value) {
            lock (this) {
                var database = key.Database;
                var tableKey = key.RowId.TableId;
                var row = key.RowId.RowNumber;
                var columnIndex = key.ColumnOffset;

                object obj;
                if (!cache.TryGet(new CacheKey(database, tableKey, row, (short)columnIndex), out obj)) { 
                    value = null;
                    return false;
                }

                value = (DataObject) obj;
                return true;
            }
        }

        public void Remove(CellKey key) {
            Remove(key.Database, key.RowId.TableId, key.RowId.RowNumber, key.ColumnOffset);
        }

        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;
            }
        }

#region Cache

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

            public Cache(TableCellCache tableCache, ICache baseCache, int hashSize, int maxSize) 
                : base(baseCache) {
                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 string database;
            private readonly short column;
            private readonly int row;
            private readonly int tableId;

            public CacheKey(string database, int tableId, int row, short column) {
                this.database = database;
                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 (database.GetHashCode() + (((int)column + tableId + (row * 189977)) * 50021) << 4);
            }

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

#endregion
    }
}