增加IJsonHost.Read<T>
石头 编写于 2024-06-30 20:50:34 智能大石头 提交于 2024-07-01 00:07:23
X
using System;
using System.Collections;
using System.Collections.Generic;
using System.Data;
using System.Data.Common;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using NewLife;
using NewLife.Collections;
using NewLife.Data;
using NewLife.Reflection;
using XCode.Common;

namespace XCode.DataAccessLayer
{
    class DaMeng : RemoteDb
    {
        #region 属性
        /// <summary>返回数据库类型。外部DAL数据库类请使用Other</summary>
        public override DatabaseType Type => DatabaseType.DaMeng;

        private static DbProviderFactory _Factory;
        /// <summary>工厂</summary>
        public override DbProviderFactory Factory
        {
            get
            {
                if (_Factory == null)
                {
                    lock (typeof(DaMeng))
                    {
#if !__CORE__
                        _Factory = DbProviderFactories.GetFactory("Dm");
#endif
                        if (_Factory == null) _Factory = GetProviderFactory("DmProvider.dll", "Dm.DmClientFactory");
                    }
                }

                return _Factory;
            }
        }

        const String Server_Key = "Server";
        protected override void OnSetConnectionString(ConnectionStringBuilder builder)
        {
            base.OnSetConnectionString(builder);

            var key = builder[Server_Key];
            if (key.EqualIgnoreCase(".", "localhost"))
            {
                builder[Server_Key] = "localhost";
            }
        }
        #endregion

        #region 方法
        /// <summary>创建数据库会话</summary>
        /// <returns></returns>
        protected override IDbSession OnCreateSession() => new DaMengSession(this);

        /// <summary>创建元数据对象</summary>
        /// <returns></returns>
        protected override IMetaData OnCreateMetaData() => new DaMengMeta();

        public override Boolean Support(String providerName)
        {
            providerName = providerName.ToLower();
            if (providerName.Contains("dameng")) return true;
            if (providerName == "dm") return true;

            return false;
        }
        #endregion

        #region 数据库特性
        ///// <summary>已重载。格式化时间</summary>
        ///// <param name="dt"></param>
        ///// <returns></returns>
        //public override String FormatDateTime(DateTime dt)
        //{
        //    if (dt.Hour == 0 && dt.Minute == 0 && dt.Second == 0) return "To_Date('{0:yyyy-MM-dd}', 'YYYY-MM-DD')".F(dt);

        //    return "To_Date('{0:yyyy-MM-dd HH:mm:ss}', 'YYYY-MM-DD HH24:MI:SS')".F(dt);
        //}

        public override String FormatValue(IDataColumn field, Object value)
        {
            var code = System.Type.GetTypeCode(field.DataType);
            var isNullable = field.Nullable;

            if (code == TypeCode.String)
            {
                if (value == null) return isNullable ? "null" : "''";

                if (field.RawType.StartsWithIgnoreCase("n"))
                    return "N'" + value.ToString().Replace("'", "''") + "'";
                else
                    return "'" + value.ToString().Replace("'", "''") + "'";
            }

            return base.FormatValue(field, value);
        }

        ///// <summary>格式化标识列,返回插入数据时所用的表达式,如果字段本身支持自增,则返回空</summary>
        ///// <param name="field">字段</param>
        ///// <param name="value">数值</param>
        ///// <returns></returns>
        //public override String FormatIdentity(IDataColumn field, Object value) => String.Format("SEQ_{0}.nextval", field.Table.TableName);

        internal protected override String ParamPrefix => ":";

        /// <summary>字符串相加</summary>
        /// <param name="left"></param>
        /// <param name="right"></param>
        /// <returns></returns>
        public override String StringConcat(String left, String right) => (!String.IsNullOrEmpty(left) ? left : "\'\'") + "||" + (!String.IsNullOrEmpty(right) ? right : "\'\'");

        /// <summary>创建参数</summary>
        /// <param name="name">名称</param>
        /// <param name="value">值</param>
        /// <param name="type">类型</param>
        /// <returns></returns>
        public override IDataParameter CreateParameter(String name, Object value, Type type = null)
        {
            //var type = field?.DataType;
            if (type == null)
            {
                type = value?.GetType();
                // 参数可能是数组
                if (type != null && type != typeof(Byte[]) && type.IsArray) type = type.GetElementTypeEx();
            }

            if (type == typeof(Boolean))
            {
                if (value is IEnumerable<Object> list)
                    value = list.Select(e => e.ToBoolean() ? 1 : 0).ToArray();
                else if (value is IEnumerable<Boolean> list2)
                    value = list2.Select(e => e.ToBoolean() ? 1 : 0).ToArray();
                else
                    value = value.ToBoolean() ? 1 : 0;

                //type = typeof(Int32);
                var dp2 = Factory.CreateParameter();
                dp2.ParameterName = FormatParameterName(name);
                dp2.Direction = ParameterDirection.Input;
                dp2.DbType = DbType.Int32;
                dp2.Value = value;
                return dp2;
            }

            var dp = base.CreateParameter(name, value, type);

            // 修正时间映射
            if (type == typeof(DateTime)) dp.DbType = DbType.Date;

            return dp;
        }
        #endregion

        #region 关键字
        protected override String ReservedWordsStr
        {
            get
            {
                return "ALL,ALTER,AND,ANY,AS,ASC,BETWEEN,BY,CHAR,CHECK,CLUSTER,COMPRESS,CONNECT,CREATE,DATE,DECIMAL,DEFAULT,DELETE,DESC,DISTINCT,DROP,ELSE,EXCLUSIVE,EXISTS,FLOAT,FOR,FROM,GRANT,GROUP,HAVING,IDENTIFIED,IN,INDEX,INSERT,INTEGER,INTERSECT,INTO,IS,LIKE,LOCK,LONG,MINUS,MODE,NOCOMPRESS,NOT,NOWAIT,NULL,NUMBER,OF,ON,OPTION,OR,ORDER,PCTFREE,PRIOR,PUBLIC,RAW,RENAME,RESOURCE,REVOKE,SELECT,SET,SHARE,SIZE,SMALLINT,START,SYNONYM,TABLE,THEN,TO,TRIGGER,UNION,UNIQUE,UPDATE,VALUES,VARCHAR,VARCHAR2,VIEW,WHERE,WITH," +
                  "Sort,Level,User,Online";
            }
        }

        /// <summary>格式化关键字</summary>
        /// <param name="keyWord">表名</param>
        /// <returns></returns>
        public override String FormatKeyWord(String keyWord)
        {
            //return String.Format("\"{0}\"", keyWord);

            //if (String.IsNullOrEmpty(keyWord)) throw new ArgumentNullException("keyWord");
            if (String.IsNullOrEmpty(keyWord)) return keyWord;

            var pos = keyWord.LastIndexOf(".");

            if (pos < 0) return "\"" + keyWord + "\"";

            var tn = keyWord.Substring(pos + 1);
            if (tn.StartsWith("\"")) return keyWord;

            return keyWord.Substring(0, pos + 1) + "\"" + tn + "\"";
        }
        #endregion
    }

    /// <summary>DaMeng数据库</summary>
    internal class DaMengSession : RemoteDbSession
    {
        #region 构造函数
        public DaMengSession(IDatabase db) : base(db) { }
        #endregion

        #region 基本方法 查询/执行
        /// <summary>快速查询单表记录数,稍有偏差</summary>
        /// <param name="tableName"></param>
        /// <returns></returns>
        public override Int64 QueryCountFast(String tableName)
        {
            if (String.IsNullOrEmpty(tableName)) return 0;

            var p = tableName.LastIndexOf(".");
            if (p >= 0 && p < tableName.Length - 1) tableName = tableName.Substring(p + 1);
            tableName = tableName.ToUpper();

            var owner = (Database as DaMeng).Owner;
            if (owner.IsNullOrEmpty()) owner = (Database as DaMeng).User;
            //var owner = (Database as DaMeng).Owner.ToUpper();
            owner = owner.ToUpper();

            //var sql = String.Format("select NUM_ROWS from sys.all_indexes where TABLE_OWNER='{0}' and TABLE_NAME='{1}' and UNIQUENESS='UNIQUE'", owner, tableName);
            // 某些表没有聚集索引,导致查出来的函数为零
            var sql = $"select NUM_ROWS from all_tables where OWNER='{owner}' and TABLE_NAME='{tableName}'";
            return ExecuteScalar<Int64>(sql);
        }

        static readonly Regex reg_SEQ = new(@"\b(\w+)\.nextval\b", RegexOptions.IgnoreCase | RegexOptions.Compiled);
        /// <summary>执行插入语句并返回新增行的自动编号</summary>
        /// <param name="sql">SQL语句</param>
        /// <param name="type">命令类型,默认SQL文本</param>
        /// <param name="ps">命令参数</param>
        /// <returns>新增行的自动编号</returns>
        public override Int64 InsertAndGetIdentity(String sql, CommandType type = CommandType.Text, params IDataParameter[] ps)
        {
            BeginTransaction(IsolationLevel.Serializable);
            try
            {
                Int64 rs = Execute(sql, type, ps);
                if (rs > 0)
                {
                    var m = reg_SEQ.Match(sql);
                    if (m != null && m.Success && m.Groups != null && m.Groups.Count > 0)
                        rs = ExecuteScalar<Int64>($"Select {m.Groups[1].Value}.currval From dual");
                }
                Commit();
                return rs;
            }
            catch { Rollback(true); throw; }
        }

#if !NET40
        public override Task<Int64> QueryCountFastAsync(String tableName)
        {
            if (String.IsNullOrEmpty(tableName)) return Task.FromResult(0L);

            var p = tableName.LastIndexOf(".");
            if (p >= 0 && p < tableName.Length - 1) tableName = tableName.Substring(p + 1);
            tableName = tableName.ToUpper();

            var owner = (Database as DaMeng).Owner;
            if (owner.IsNullOrEmpty()) owner = (Database as DaMeng).User;
            owner = owner.ToUpper();

            // 某些表没有聚集索引,导致查出来的函数为零
            var sql = $"select NUM_ROWS from all_tables where OWNER='{owner}' and TABLE_NAME='{tableName}'";
            return ExecuteScalarAsync<Int64>(sql);
        }

        public override async Task<Int64> InsertAndGetIdentityAsync(String sql, CommandType type = CommandType.Text, params IDataParameter[] ps)
        {
            BeginTransaction(IsolationLevel.Serializable);
            try
            {
                Int64 rs = await ExecuteAsync(sql, type, ps);
                if (rs > 0)
                {
                    var m = reg_SEQ.Match(sql);
                    if (m != null && m.Success && m.Groups != null && m.Groups.Count > 0)
                        rs = await ExecuteScalarAsync<Int64>($"Select {m.Groups[1].Value}.currval From dual");
                }
                Commit();
                return rs;
            }
            catch { Rollback(true); throw; }
        }
#endif

        /// <summary>重载支持批量操作</summary>
        /// <param name="sql"></param>
        /// <param name="type"></param>
        /// <param name="ps"></param>
        /// <returns></returns>
        protected override DbCommand OnCreateCommand(String sql, CommandType type = CommandType.Text, params IDataParameter[] ps)
        {
            var cmd = base.OnCreateCommand(sql, type, ps);
            if (cmd == null) return null;

            // 如果参数Value都是数组,那么就是批量操作
            if (ps != null && ps.Length > 0 && ps.All(p => p.Value is IList))
            {
                var arr = ps.First().Value as IList;
                cmd.SetValue("ArrayBindCount", arr.Count);
                cmd.SetValue("BindByName", true);

                // 超时时间放大10倍
                if (cmd.CommandTimeout > 0)
                    cmd.CommandTimeout *= 10;
                else
                    cmd.CommandTimeout = 120;
            }

            return cmd;
        }
        #endregion

        #region 批量操作
        public override Int32 Insert(IDataTable table, IDataColumn[] columns, IEnumerable<IExtend> list)
        {
            var ps = new HashSet<String>();
            var sql = GetInsertSql(table, columns, ps);
            var dps = GetParameters(columns, ps, list);

            return Execute(sql, CommandType.Text, dps);
        }

        private String GetInsertSql(IDataTable table, IDataColumn[] columns, ICollection<String> ps)
        {
            var sb = Pool.StringBuilder.Get();
            var db = Database as DbBase;

            // 字段列表
            sb.AppendFormat("Insert Into {0}(", db.FormatName(table));
            foreach (var dc in columns)
            {
                //if (dc.Identity) continue;

                sb.Append(db.FormatName(dc));
                sb.Append(',');
            }
            sb.Length--;
            sb.Append(')');

            // 值列表
            sb.Append(" Values(");
            foreach (var dc in columns)
            {
                //if (dc.Identity) continue;

                sb.Append(db.FormatParameterName(dc.Name));
                sb.Append(',');

                if (!ps.Contains(dc.Name)) ps.Add(dc.Name);
            }
            sb.Length--;
            sb.Append(')');

            return sb.Put(true);
        }

        private IDataParameter[] GetParameters(IDataColumn[] columns, ICollection<String> ps, IEnumerable<IExtend> list)
        {
            var db = Database;
            var dps = new List<IDataParameter>();
            foreach (var dc in columns)
            {
                //if (dc.Identity) continue;
                if (!ps.Contains(dc.Name)) continue;

                //var vs = new List<Object>();
                var type = dc.DataType;
                if (!type.IsInt() && type.IsEnum) type = typeof(Int32);
                var arr = Array.CreateInstance(type, list.Count());
                var k = 0;
                foreach (var entity in list)
                {
                    //vs.Add(entity[dc.Name]);
                    arr.SetValue(entity[dc.Name], k++);
                }
                var dp = db.CreateParameter(dc.Name, arr, dc);

                dps.Add(dp);
            }

            return dps.ToArray();
        }

        public override Int32 Upsert(IDataTable table, IDataColumn[] columns, ICollection<String> updateColumns, ICollection<String> addColumns, IEnumerable<IExtend> list)
        {
            var ps = new HashSet<String>();
            var insert = GetInsertSql(table, columns, ps);
            var update = GetUpdateSql(table, columns, updateColumns, addColumns, ps);

            var sb = Pool.StringBuilder.Get();
            sb.AppendLine("BEGIN");
            sb.AppendLine(insert + ";");
            sb.AppendLine("EXCEPTION");
            // 没有更新时,直接返回,可用于批量插入且其中部分有冲突需要忽略的场景
            if (!update.IsNullOrEmpty())
            {
                sb.AppendLine("WHEN DUP_VAL_ON_INDEX THEN");
                sb.AppendLine(update + ";");
            }
            else
            {
                //sb.AppendLine("WHEN OTHERS THEN");
                sb.AppendLine("WHEN DUP_VAL_ON_INDEX THEN");
                sb.AppendLine("RETURN;");
            }
            sb.AppendLine("END;");

            var sql = sb.Put(true);

            var dps = GetParameters(columns, ps, list);

            return Execute(sql, CommandType.Text, dps);
        }

        private String GetUpdateSql(IDataTable table, IDataColumn[] columns, ICollection<String> updateColumns, ICollection<String> addColumns, ICollection<String> ps)
        {
            if ((updateColumns == null || updateColumns.Count == 0)
                && (addColumns == null || addColumns.Count == 0)) return null;

            var sb = Pool.StringBuilder.Get();
            var db = Database as DbBase;

            // 字段列表
            sb.AppendFormat("Update {0} Set ", db.FormatName(table));
            foreach (var dc in columns)
            {
                if (dc.Identity || dc.PrimaryKey) continue;

                if (addColumns != null && addColumns.Contains(dc.Name))
                {
                    sb.AppendFormat("{0}={0}+{1},", db.FormatName(dc), db.FormatParameterName(dc.Name));

                    if (!ps.Contains(dc.Name)) ps.Add(dc.Name);
                }
                else if (updateColumns != null && updateColumns.Contains(dc.Name))
                {
                    sb.AppendFormat("{0}={1},", db.FormatName(dc), db.FormatParameterName(dc.Name));

                    if (!ps.Contains(dc.Name)) ps.Add(dc.Name);
                }
            }
            sb.Length--;

            // 条件
            sb.Append(" Where ");
            foreach (var dc in columns)
            {
                if (!dc.PrimaryKey) continue;

                sb.AppendFormat("{0}={1}", db.FormatName(dc), db.FormatParameterName(dc.Name));
                sb.Append(" And ");

                if (!ps.Contains(dc.Name)) ps.Add(dc.Name);
            }
            sb.Length -= " And ".Length;

            return sb.Put(true);
        }

        public override Int32 Update(IDataTable table, IDataColumn[] columns, ICollection<String> updateColumns, ICollection<String> addColumns, IEnumerable<IExtend> list)
        {
            var ps = new HashSet<String>();
            var sql = GetUpdateSql(table, columns, updateColumns, addColumns, ps);
            var dps = GetParameters(columns, ps, list);

            return Execute(sql, CommandType.Text, dps);
        }
        #endregion
    }

    /// <summary>DaMeng元数据</summary>
    class DaMengMeta : RemoteDbMetaData
    {
        public DaMengMeta() => Types = _DataTypes;

        /// <summary>拥有者</summary>
        public String Owner
        {
            get
            {
                var owner = Database.Owner;
                if (owner.IsNullOrEmpty()) owner = (Database as DaMeng).User;

                return owner;
            }
        }

        /// <summary>用户名</summary>
        public String UserID => (Database as DaMeng).User.ToUpper();

        /// <summary>取得所有表构架</summary>
        /// <returns></returns>
        protected override List<IDataTable> OnGetTables(String[] names)
        {
            DataTable dt = null;

            // 不缺分大小写,并且不是保留字,才转大写
            if (names != null)
            {
                var db = Database as DaMeng;
                /*if (db.IgnoreCase)*/
                names = names.Select(e => db.IsReservedWord(e) ? e : e.ToUpper()).ToArray();
            }

            // 采用集合过滤,提高效率
            String tableName = null;
            if (names != null && names.Length == 1) tableName = names.FirstOrDefault();
            if (tableName.IsNullOrEmpty()) tableName = null;

            var owner = Owner;
            //if (owner.IsNullOrEmpty()) owner = UserID;

            //dt = Get("all_tables", owner, tableName);
            dt = GetSchema(_.Tables, new String[] { owner, tableName });
            if (!dt.Columns.Contains("TABLE_TYPE"))
            {
                dt.Columns.Add("TABLE_TYPE", typeof(String));
                foreach (var dr in dt.Rows?.ToArray())
                {
                    dr["TABLE_TYPE"] = "Table";
                }
            }
            var dtView = GetSchema(_.Views, new String[] { owner, tableName });
            if (dtView != null && dtView.Rows.Count != 0)
            {
                foreach (var dr in dtView.Rows?.ToArray())
                {
                    var drNew = dt.NewRow();
                    drNew["OWNER"] = dr["OWNER"];
                    drNew["TABLE_NAME"] = dr["VIEW_NAME"];
                    drNew["TABLE_TYPE"] = "View";
                    dt.Rows.Add(drNew);
                }
            }

            var data = new NullableDictionary<String, DataTable>(StringComparer.OrdinalIgnoreCase);

            // 如果表太多,则只要目标表数据
            var mulTable = "";
            if (dt.Rows.Count > 10 && names != null && names.Length > 0)
            {
                //var tablenames = dt.Rows.ToArray().Select(e => "'{0}'".F(e["TABLE_NAME"]));
                //mulTable = " And TABLE_NAME in ({0})".F(tablenames.Join(","));
                mulTable = $" And TABLE_NAME in ({names.Select(e => $"'{e}'").Join(",")})";
            }

            // 列和索引
            data["Columns"] = Get("all_tab_columns", owner, tableName, mulTable);
            data["Indexes"] = Get("all_indexes", owner, tableName, mulTable);
            data["IndexColumns"] = Get("all_ind_columns", owner, tableName, mulTable, "Table_Owner");

            // 主键
            if (MetaDataCollections.Contains(_.PrimaryKeys) && !tableName.IsNullOrEmpty()) data["PrimaryKeys"] = GetSchema(_.PrimaryKeys, new String[] { owner, tableName, null });

            // 序列
            data["Sequences"] = Get("all_sequences", owner, null, null, "Sequence_Owner");

            // 表注释
            data["TableComment"] = Get("all_tab_comments", owner, tableName, mulTable);

            // 列注释
            data["ColumnComment"] = Get("all_col_comments", owner, tableName, mulTable, "SCHEMA_NAME");

            var list = GetTables(dt.Rows.ToArray(), names, data);

            return list;
        }

        /// <summary>
        /// 快速取得所有表名
        /// </summary>
        /// <returns></returns>
        public override IList<String> GetTableNames()
        {
            var list = new List<String>();

            var dt = GetSchema(_.Tables, new String[] { Owner, null });
            if (dt?.Rows == null || dt.Rows.Count < 1) return list;

            foreach (DataRow dr in dt.Rows)
            {
                list.Add(GetDataRowValue<String>(dr, _.TalbeName));
            }

            return list;
        }

        private DataTable Get(String name, String owner, String tableName, String mulTable = null, String ownerName = null)
        {
            if (ownerName.IsNullOrEmpty()) ownerName = "Owner";
            var sql = $"Select * From {name} Where {ownerName}='{owner}'";
            if (!tableName.IsNullOrEmpty())
                sql += $" And TABLE_NAME='{tableName}'";
            else if (!mulTable.IsNullOrEmpty())
                sql += mulTable;

            return Database.CreateSession().Query(sql).Tables[0];
        }

        protected override void FixTable(IDataTable table, DataRow dr, IDictionary<String, DataTable> data)
        {
            base.FixTable(table, dr, data);

            // 主键
            var dt = data?["PrimaryKeys"];
            if (dt != null && dt.Rows.Count > 0)
            {
                var drs = dt.Select($"{_.TalbeName}='{table.TableName}'");
                if (drs != null && drs.Length > 0)
                {
                    // 找到主键所在索引,这个索引的列才是主键
                    if (TryGetDataRowValue(drs[0], _.IndexName, out String name) && !String.IsNullOrEmpty(name))
                    {
                        var di = table.Indexes.FirstOrDefault(i => i.Name == name);
                        if (di != null)
                        {
                            di.PrimaryKey = true;
                            foreach (var dc in table.Columns)
                            {
                                dc.PrimaryKey = di.Columns.Contains(dc.ColumnName);
                            }
                        }
                    }
                }
            }

            // 表注释 USER_TAB_COMMENTS
            table.Description = GetTableComment(table.TableName, data);

            if (table?.Columns == null || table.Columns.Count == 0) return;
        }

        String GetTableComment(String name, IDictionary<String, DataTable> data)
        {
            var dt = data?["TableComment"];
            if (dt?.Rows == null || dt.Rows.Count < 1) return null;

            var where = $"TABLE_NAME='{name}'";
            var drs = dt.Select(where);
            if (drs != null && drs.Length > 0) return Convert.ToString(drs[0]["COMMENTS"]);

            return null;
        }

        /// <summary>取得指定表的所有列构架</summary>
        /// <param name="table"></param>
        /// <param name="columns">列</param>
        /// <param name="data"></param>
        /// <returns></returns>
        protected override List<IDataColumn> GetFields(IDataTable table, DataTable columns, IDictionary<String, DataTable> data)
        {
            var list = base.GetFields(table, columns, data);
            if (list == null || list.Count < 1) return null;

            // 字段注释
            if (list != null && list.Count > 0)
            {
                foreach (var field in list)
                {
                    field.Description = GetColumnComment(table.TableName, field.ColumnName, data);
                }
            }

            return list;
        }

        const String KEY_OWNER = "OWNER";

        protected override List<IDataColumn> GetFields(IDataTable table, DataRow[] rows)
        {
            if (rows == null || rows.Length < 1) return null;

            var owner = Owner;
            if (owner.IsNullOrEmpty() || !rows[0].Table.Columns.Contains(KEY_OWNER)) return base.GetFields(table, rows);

            var list = new List<DataRow>();
            foreach (var dr in rows)
            {
                if (TryGetDataRowValue(dr, KEY_OWNER, out String str) && owner.EqualIgnoreCase(str)) list.Add(dr);
            }

            return base.GetFields(table, list.ToArray());
        }

        String GetColumnComment(String tableName, String columnName, IDictionary<String, DataTable> data)
        {
            var dt = data?["ColumnComment"];
            if (dt?.Rows == null || dt.Rows.Count < 1) return null;

            var where = $"{_.TalbeName}='{tableName}' AND {_.ColumnName}='{columnName}'";
            var drs = dt.Select(where);
            if (drs != null && drs.Length > 0) return Convert.ToString(drs[0]["COMMENTS"]);
            return null;
        }

        protected override void FixField(IDataColumn field, DataRow drColumn)
        {
            var dr = drColumn;

            // 长度
            //field.Length = GetDataRowValue<Int32>(dr, "CHAR_LENGTH", "DATA_LENGTH");
            field.Length = GetDataRowValue<Int32>(dr, "DATA_LENGTH");

            if (field is XField fi)
            {
                // 精度 与 位数
                fi.Precision = GetDataRowValue<Int32>(dr, "DATA_PRECISION");
                fi.Scale = GetDataRowValue<Int32>(dr, "DATA_SCALE");
                if (field.Length == 0) field.Length = fi.Precision;
            }

            // 长度
            if (TryGetDataRowValue(drColumn, "LENGTHINCHARS", out Int32 len) && len > 0) field.Length = len;

            base.FixField(field, drColumn);
        }

        protected override void FixIndex(IDataIndex index, DataRow dr)
        {
            if (TryGetDataRowValue(dr, "UNIQUENESS", out String str))
                index.Unique = str == "UNIQUE";

            base.FixIndex(index, dr);
        }

        /// <summary>数据类型映射</summary>
        private static readonly Dictionary<Type, String[]> _DataTypes = new()
        {
            { typeof(Byte[]), new String[] { "BLOB", "BINARY", "VARBINARY" } },
            { typeof(Boolean), new String[] { "BIT" } },
            { typeof(Byte), new String[] { "TINYINT" } },
            { typeof(Int16), new String[] { "SMALLINT" } },
            { typeof(Int32), new String[] { "INT" } },
            { typeof(Int64), new String[] { "BIGINT" } },
            { typeof(Single), new String[] { "REAL" } },
            { typeof(Double), new String[] { "DOUBLE" } },
            { typeof(Decimal), new String[] { "DEC" } },
            { typeof(DateTime), new String[] { "DATETIME", "TIME", "DATE", "TIMESTAMP" } },
            { typeof(String), new String[] { "VARCHAR({0})", "TEXT", "CHAR", "CLOB" } }
        };

        #region 架构定义
        public override Object SetSchema(DDLSchema schema, params Object[] values)
        {
            var session = Database.CreateSession();

            var dbname = String.Empty;
            var databaseName = String.Empty;
            switch (schema)
            {
                case DDLSchema.DatabaseExist:
                    // DaMeng不支持判断数据库是否存在
                    return true;

                default:
                    break;
            }
            return base.SetSchema(schema, values);
        }

        public override String DatabaseExistSQL(String dbname) => String.Empty;

        protected override String GetFieldConstraints(IDataColumn field, Boolean onlyDefine)
        {
            var str = field.Nullable ? " NULL" : " NOT NULL";

            if (field.Identity) str = " IDENTITY NOT NULL";

            return str;
        }

        //protected override String GetDefault(IDataColumn field, Boolean onlyDefine)
        //{
        //    if (field.DataType == typeof(DateTime)) return " DEFAULT To_Date('0001-01-01','yyyy-mm-dd')";

        //    return base.GetDefault(field, onlyDefine);
        //}

        public override String CreateTableSQL(IDataTable table)
        {
            var fs = new List<IDataColumn>(table.Columns);

            var sb = new StringBuilder(32 + fs.Count * 20);

            sb.AppendFormat("Create Table {0}(", FormatName(table));
            for (var i = 0; i < fs.Count; i++)
            {
                sb.AppendLine();
                sb.Append('\t');
                sb.Append(FieldClause(fs[i], true));
                if (i < fs.Count - 1) sb.Append(',');
            }

            // 主键
            var pks = table.PrimaryKeys;
            if (pks != null && pks.Length > 0) sb.AppendFormat(",\r\n\tprimary key ({0})", pks.Join(",", FormatName));

            sb.AppendLine();
            sb.Append(')');

            var sql = sb.ToString();
            if (sql.IsNullOrEmpty()) return sql;

            // 去掉分号后的空格,DaMeng不支持同时执行多个语句
            return sb.ToString();
        }

        //public override String DropTableSQL(String tableName)
        //{
        //    var sql = base.DropTableSQL(tableName);
        //    if (String.IsNullOrEmpty(sql)) return sql;

        //    var sqlSeq = String.Format("Drop Sequence SEQ_{0}", tableName);
        //    return sql + "; " + Environment.NewLine + sqlSeq;
        //}

        public override String AddColumnSQL(IDataColumn field) => $"Alter Table {FormatName(field.Table)} Add {FieldClause(field, true)}";

        public override String AlterColumnSQL(IDataColumn field, IDataColumn oldfield) => $"Alter Table {FormatName(field.Table)} Modify {FieldClause(field, false)}";

        public override String DropColumnSQL(IDataColumn field) => $"Alter Table {FormatName(field.Table)} Drop Column {field}";

        public override String AddTableDescriptionSQL(IDataTable table) => $"Comment On Table {FormatName(table)} is '{table.Description}'";

        public override String DropTableDescriptionSQL(IDataTable table) => $"Comment On Table {FormatName(table)} is ''";

        public override String AddColumnDescriptionSQL(IDataColumn field) => $"Comment On Column {FormatName(field.Table)}.{FormatName(field)} is '{field.Description}'";

        public override String DropColumnDescriptionSQL(IDataColumn field) => $"Comment On Column {FormatName(field.Table)}.{FormatName(field)} is ''";
        #endregion
    }
}