在.net中使用aquiles访问Cassandra(二)

上文中我们已经建立了项目的基本结构，今天实现数据的修改。在NoSQL中，通常添加和修改都认为是对数据的一种Mutation。

 

1.建立描述修改Row的实体。

    public class RowMutation

    {

        public string Key { get; set; }



        public IList<CellMutation> Mutations { get; set; }



        public RowMutation()

        {



        }



        public RowMutation(string key)

        {

            Key = key;

        }



        public RowMutation(string key, IList<CellMutation> mutations)

        {

            Key = key;

            Mutations = mutations;

        }

    }



    public class CellMutation

    {

        public string ColumnName { get; set; }



        public string DataValue { get; set; }



        public CellMutation()

        {



        }



        public CellMutation(string name)

        {

            ColumnName = name;

        }



        public CellMutation(string name, string value)

        {

            ColumnName = name;

            DataValue = value;

        }

    }

View Code

2.引用aquiles命名空间。

using Aquiles.Helpers.Encoders;

using Aquiles.Cassandra10;

using Aquiles.Core.Cluster;

3.初始化成员变量

        private string _clusterName { get; set; }

        private ConsistencyLevel _consistencyLevel { get; set; }

        private string _keyspaceName { get; set; }

        private ICluster _cluster = null;



        public AquilesDemo()

        {

            _clusterName = "xxxx";

            _consistencyLevel = ConsistencyLevel.LOCAL_QUORUM;

           _keyspaceName = "xxxx";



            _cluster = AquilesHelper.RetrieveCluster(_clusterName);

        }

4.建立一个通用的修改多行多列的方法，其它改变方式可以在此基础上完成调用，如修改一多一列，一行多列等。

       public void Mutate(string columnFamily, IList<RowMutation> rowMutations)

        {

            if (string.IsNullOrWhiteSpace(columnFamily)) throw new ArgumentNullException("columnFamily");



            rowMutations = PrepareMutationList(rowMutations);

            Dictionary<byte[], Dictionary<string, List<Apache.Cassandra.Mutation>>> mutation_map = new Dictionary<byte[], Dictionary<string, List<Apache.Cassandra.Mutation>>>();



            foreach (var rowMutation in rowMutations)

            {

                byte[] key = ByteEncoderHelper.UTF8Encoder.ToByteArray(rowMutation.Key);



                Dictionary<string, List<Apache.Cassandra.Mutation>> cfMutation = new Dictionary<string, List<Apache.Cassandra.Mutation>>();

                List<Apache.Cassandra.Mutation> mutationList = new List<Apache.Cassandra.Mutation>();



                foreach (CellMutation cellMutation in rowMutation.Mutations)

                {

                    if (cellMutation.DataValue == null) continue;



                    Apache.Cassandra.Mutation mutation = new Apache.Cassandra.Mutation()

                    {

                        Column_or_supercolumn = new ColumnOrSuperColumn()

                        {

                            Column = new Column()

                            {

                                Name = ByteEncoderHelper.UTF8Encoder.ToByteArray(cellMutation.ColumnName),

                                Timestamp = DateTime.Now.ToUnixTimestamp(),

                                Value = ByteEncoderHelper.UTF8Encoder.ToByteArray(cellMutation.DataValue),

                            },

                        },

                    };

                    mutationList.Add(mutation);

                }



                if (mutationList.Count > 0)

                {

                    cfMutation.Add(columnFamily, mutationList);

                    mutation_map.Add(key, cfMutation);

                }

            }



            if (mutation_map.Count == 0) return;

            _cluster.Execute(new ExecutionBlock(delegate(Apache.Cassandra.Cassandra.Client client)

            {

                client.batch_mutate(mutation_map, _consistencyLevel);

                return null;

            }), _keyspaceName);



        }

 5. 由于调用端可能会将同一行的修改分为多个RowMutation传入，所以上面的代码使用PrepareMutationList方法根据RowKey作了聚合处理。

        /// <summary>

        /// 聚合列表中相同rowkey的项为同一Mutation。

        /// </summary>

        /// <param name="rowMutations"></param>

        /// <returns></returns>

        private IList<RowMutation> PrepareMutationList(IList<RowMutation> rowMutations)

        {

            if (rowMutations == null) return null;



            //按rowkey分组

            var rowMutationGroups = rowMutations.GroupBy(rm => rm.Key);



            //分组后的总数量相同，则认为rowkey在列表中是唯一的，不用做聚合处理

            if (rowMutations.Count == rowMutationGroups.Count()) return rowMutations;



            //遍历分组结果

            IList<RowMutation> result = new List<RowMutation>();

            foreach (var rmg in rowMutationGroups)

            {

                RowMutation rowMutation = new RowMutation();

                rowMutation.Key = rmg.Key;



                //将同一分组的所有CellMutation放在一个列表中

                List<CellMutation> cellMutations = new List<CellMutation>();

                foreach (var rm in rmg)

                {

                    cellMutations.AddRange(rm.Mutations);

                }



                if (cellMutations.Count() > 0)

                {

                    rowMutation.Mutations = cellMutations;

                    result.Add(rowMutation);

                }

            }

            return result;

        }