// Npgsql.NpgsqlDataReader.cs
//
// Author:
//	Francisco Jr. (fxjrlists@yahoo.com.br)
//
//	Copyright (C) 2002 The Npgsql Development Team
//	npgsql-general@gborg.postgresql.org
//	http://gborg.postgresql.org/project/npgsql/projdisplay.php
//
//
// Permission to use, copy, modify, and distribute this software and its
// documentation for any purpose, without fee, and without a written
// agreement is hereby granted, provided that the above copyright notice
// and this paragraph and the following two paragraphs appear in all copies.
// 
// IN NO EVENT SHALL THE NPGSQL DEVELOPMENT TEAM BE LIABLE TO ANY PARTY
// FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES,
// INCLUDING LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
// DOCUMENTATION, EVEN IF THE NPGSQL DEVELOPMENT TEAM HAS BEEN ADVISED OF
// THE POSSIBILITY OF SUCH DAMAGE.
// 
// THE NPGSQL DEVELOPMENT TEAM SPECIFICALLY DISCLAIMS ANY WARRANTIES,
// INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
// AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
// ON AN "AS IS" BASIS, AND THE NPGSQL DEVELOPMENT TEAM HAS NO OBLIGATIONS
// TO PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.

using System;
using System.Collections;
using System.Collections.Generic;
using System.Data;
using System.Data.Common;
using System.Text;
using System.Reflection;
using System.Threading;
using NpgsqlTypes;

namespace Npgsql
{
	/// <summary>
	/// Provides a means of reading a forward-only stream of rows from a PostgreSQL backend.  This class cannot be inherited.
	/// </summary>
	public abstract class NpgsqlDataReader : DbDataReader
	{
		//NpgsqlDataReader is abstract because the desired implementation depends upon whether the user
		//is using the backwards-compatibility option of preloading the entire reader (configurable from the
		//connection string).
		//Everything that can be done here is, but where the implementation must be different between the
		//two modi operandi, that code will differ between the two implementations, ForwardsOnlyDataReader
		//and CachingDataReader.
		//Since the concrete classes are internal and returned to the user through an NpgsqlDataReader reference,
		//the differences between the two is hidden from the user. Because CachingDataReader is a less efficient
		//class supplied only to resolve some backwards-compatibility issues that are possible with some code, all
		//internal use uses ForwardsOnlyDataReader directly.
		internal NpgsqlConnector _connector;
		internal NpgsqlConnection _connection;
		internal DataTable _currentResultsetSchema;
		internal CommandBehavior _behavior;
		internal NpgsqlCommand _command;

        internal Version Npgsql205 = new Version("2.0.5");

		internal NpgsqlDataReader(NpgsqlCommand command, CommandBehavior behavior)
		{
			_behavior = behavior;
			_connection = (_command = command).Connection;
			_connector = command.Connector;
		}

		internal bool _isClosed = false;

		/// <summary>
		/// Is raised whenever Close() is called.
		/// </summary>
		public event EventHandler ReaderClosed;

		internal abstract long? LastInsertedOID { get; }

		internal bool TryGetTypeInfo(int fieldIndex, out NpgsqlBackendTypeInfo backendTypeInfo)
		{
			if (CurrentDescription == null)
			{
				throw new IndexOutOfRangeException(); //Essentially, all indices are out of range.
			}
			return (backendTypeInfo = CurrentDescription[fieldIndex].TypeInfo) != null;
		}

		internal abstract void CheckHaveRow();
		internal abstract NpgsqlRowDescription CurrentDescription { get; }

		/// <summary>
		/// Return the data type name of the column at index <param name="Index"></param>.
		/// </summary>
		public override String GetDataTypeName(Int32 Index)
		{
			NpgsqlBackendTypeInfo TI;
			return TryGetTypeInfo(Index, out TI) ? TI.Name : GetDataTypeOID(Index);
		}

		/// <summary>
		/// Return the data type of the column at index <param name="Index"></param>.
		/// </summary>
		public override Type GetFieldType(Int32 Index)
		{
			NpgsqlBackendTypeInfo TI;
			return TryGetTypeInfo(Index, out TI) ? TI.FrameworkType : typeof (string); //Default type is string.
		}

        /// <summary>
        /// Return the Npgsql specific data type of the column at requested ordinal.
        /// </summary>
        /// <param name="ordinal">column position</param>
        /// <returns>Appropriate Npgsql type for column.</returns>
        public override Type GetProviderSpecificFieldType(int ordinal)
        {
            NpgsqlBackendTypeInfo TI;
            return TryGetTypeInfo(ordinal, out TI) ? TI.Type : typeof(string); //Default type is string.
        }

		/// <summary>
		/// Gets the number of columns in the current row.
		/// </summary>
		public override Int32 FieldCount
		{
			get { 
                    if (_connector.CompatVersion <= Npgsql205)
                        return CurrentDescription == null ? -1 : CurrentDescription.NumFields; 
                    else
                        // We read msdn documentation and bug report #1010649 that the common return value is 0.
                        return CurrentDescription == null ? 0 : CurrentDescription.NumFields; 
                }
		}

		/// <summary>
		/// Return the column name of the column at index <param name="Index"></param>.
		/// </summary>
		public override String GetName(Int32 Index)
		{
			if (CurrentDescription == null)
			{
				throw new IndexOutOfRangeException(); //Essentially, all indices are out of range.
			}

			return CurrentDescription[Index].Name;
		}

		/// <summary>
		/// Return the data type OID of the column at index <param name="Index"></param>.
		/// </summary>
		/// FIXME: Why this method returns String?
		public String GetDataTypeOID(Int32 Index)
		{
			if (CurrentDescription == null)
			{
				throw new IndexOutOfRangeException(); //Essentially, all indices are out of range.
			}

			return CurrentDescription[Index].TypeOID.ToString();
		}


		/// <summary>
		/// Gets the value of a column in its native format.
		/// </summary>
		public override Object this[Int32 i]
		{
			get { return GetValue(i); }
		}
		
		public bool HasOrdinal(string fieldName)
		{
		    if(CurrentDescription == null)
		        throw new InvalidOperationException("Invalid attempt to read when no data is present.");
		    return CurrentDescription.HasOrdinal(fieldName);
		}

		/// <summary>
		/// Return the column name of the column named <param name="Name"></param>.
		/// </summary>
		public override Int32 GetOrdinal(String Name)
		{
			if (CurrentDescription == null)
				throw new InvalidOperationException("Invalid attempt to read when no data is present.");
			return CurrentDescription.FieldIndex(Name);
		}


		/// <summary>
		/// Gets the value of a column in its native format.
		/// </summary>
		public override Object this[String name]
		{
			get
			{
				return GetValue(GetOrdinal(name));
			}
		}

		/// <summary>
		/// Return the data DbType of the column at index <param name="Index"></param>.
		/// </summary>
		public DbType GetFieldDbType(Int32 Index)
		{
			NpgsqlBackendTypeInfo TI;
			return TryGetTypeInfo(Index, out TI) ? TI.DbType : DbType.String;
		}

		/// <summary>
		/// Return the data NpgsqlDbType of the column at index <param name="Index"></param>.
		/// </summary>
		public NpgsqlDbType GetFieldNpgsqlDbType(Int32 Index)
		{
			NpgsqlBackendTypeInfo TI;
			return TryGetTypeInfo(Index, out TI) ? TI.NpgsqlDbType : NpgsqlDbType.Text;
		}
		
		public BitString GetBitString(int i)
		{
		    object ret = GetValue(i);
		    if(ret is bool)
		        return new BitString((bool)ret);
		    else
		        return (BitString)ret;
		}

		/// <summary>
		/// Get the value of a column as a <see cref="NpgsqlInterval"/>.
		/// <remarks>If the differences between <see cref="NpgsqlInterval"/> and <see cref="System.Timespan"/>
		/// in handling of days and months is not important to your application, use <see cref="GetTimeSpan()"/>
		/// instead.</remarks>
		/// </summary>
		/// <param name="i">Index of the field to find.</param>
		/// <returns><see cref="NpgsqlInterval"/> value of the field.</returns>
		public NpgsqlInterval GetInterval(Int32 i)
		{
            return (NpgsqlInterval)GetProviderSpecificValue(i);
		}

		public NpgsqlTime GetTime(int i)
		{
            return (NpgsqlTime)GetProviderSpecificValue(i);
		}

		public NpgsqlTimeTZ GetTimeTZ(int i)
		{
            return (NpgsqlTimeTZ)GetProviderSpecificValue(i);
		}

		public NpgsqlTimeStamp GetTimeStamp(int i)
		{
            return (NpgsqlTimeStamp)GetProviderSpecificValue(i);
		}

		public NpgsqlTimeStampTZ GetTimeStampTZ(int i)
		{
            return (NpgsqlTimeStampTZ)GetProviderSpecificValue(i);
		}

		public NpgsqlDate GetDate(int i)
		{
            return (NpgsqlDate)GetProviderSpecificValue(i);
		}

		protected void SendClosedEvent()
		{
			if (this.ReaderClosed != null)
			{
				this.ReaderClosed(this, EventArgs.Empty);
			}
		}

		/// <summary>
		/// Gets the value of a column converted to a Guid.
		/// </summary>
		public override Guid GetGuid(Int32 i)
		{
			return (Guid) GetValue(i);
		}

		/// <summary>
		/// Gets the value of a column as Int16.
		/// </summary>
		public override Int16 GetInt16(Int32 i)
		{
			return (Int16) GetValue(i);
		}

		/// <summary>
		/// Gets the value of a column as Int32.
		/// </summary>
		public override Int32 GetInt32(Int32 i)
		{
			return (Int32) GetValue(i);
		}

		/// <summary>
		/// Gets the value of a column as Int64.
		/// </summary>
		public override Int64 GetInt64(Int32 i)
		{
			return (Int64) GetValue(i);
		}

		/// <summary>
		/// Gets the value of a column as Single.
		/// </summary>
		public override Single GetFloat(Int32 i)
		{
			return (Single) GetValue(i);
		}

		/// <summary>
		/// Gets the value of a column as Double.
		/// </summary>
		public override Double GetDouble(Int32 i)
		{
			return (Double) GetValue(i);
		}

		/// <summary>
		/// Gets the value of a column as String.
		/// </summary>
		public override String GetString(Int32 i)
		{
			return (String) GetValue(i);
		}

		/// <summary>
		/// Gets the value of a column as Decimal.
		/// </summary>
		public override Decimal GetDecimal(Int32 i)
		{
			return (Decimal) GetValue(i);
		}

		/// <summary>
		/// Gets a value indicating the depth of nesting for the current row.  Always returns zero.
		/// </summary>
		public override Int32 Depth
		{
			get { return 0; }
		}

		/// <summary>
		/// Gets a value indicating whether the data reader is closed.
		/// </summary>
		public override Boolean IsClosed
		{
			get { return _isClosed; }
		}

		/// <summary>
		/// Copy values from each column in the current row into <param name="Values"></param>.
		/// </summary>
		/// <returns>The number of column values copied.</returns>
		public override Int32 GetValues(Object[] Values)
		{
            return LoadValues(Values, GetValue);
		}

        /// <summary>
        /// Copy values from each column in the current row into <param name="Values"></param>.
        /// </summary>
        /// <param name="values">An array appropriately sized to store values from all columns.</param>
        /// <returns>The number of column values copied.</returns>
        public override int GetProviderSpecificValues(object[] values)
        {
            return LoadValues(values, GetProviderSpecificValue);
        }

        private delegate object ValueLoader(int ordinal);
        private int LoadValues(object[] values, ValueLoader getValue)
        {
            CheckHaveRow();

            // Only the number of elements in the array are filled.
            // It's also possible to pass an array with more that FieldCount elements.
            Int32 maxColumnIndex = (values.Length < FieldCount) ? values.Length : FieldCount;

            for (Int32 i = 0; i < maxColumnIndex; i++)
            {
                values[i] = getValue(i);
            }

            return maxColumnIndex;
        }

		/// <summary>
		/// Gets the value of a column as Boolean.
		/// </summary>
		public override Boolean GetBoolean(Int32 i)
		{
			// Should this be done using the GetValue directly and not by converting to String
			// and parsing from there?
			return (Boolean) GetValue(i);
		}

		/// <summary>
		/// Gets the value of a column as Byte.  Not implemented.
		/// </summary>
		public override Byte GetByte(Int32 i)
		{
			throw new NotImplementedException();
		}

		/// <summary>
		/// Gets the value of a column as Char.
		/// </summary>
		public override Char GetChar(Int32 i)
		{
			//This is an interesting one. In the world of databases we've the idea of chars which is 0 to n characters
			//where n is stated (and can perhaps be infinite) and various variations upon that (postgres is admirable
			//in being relatively consistent and in not generally encouraging limiting n purely for performance reasons,
			//but across many different platforms we'll find such things as text, ntext, char, nchar, varchar, nvarchar,
			//and so on with some platforms not having them all and many implementaiton differences).
			//
			//In the world of .NET, and many other languages, we have the idea of characters and of strings - which are
			//sequences of characters with differing degress of encapsulation from C just having char* through to .NET
			//having full-blown objects
			//
			//Database char, varchar, text, etc. are all generally mapped to strings. There's a bit of a question as to
			//what maps to a .NET char. Interestingly enough, SQLDataReader doesn't support GetChar() and neither do
			//a few other providers (Oracle for example). It would seem that IDataReader.GetChar() was defined largely
			//to have a complete set of .NET base types. Still, the closets thing in the database world to a char value
			//is a char(1) or varchar(1) - that is to say the value of a string of length one, so that's what is used here.
			string s = GetString(i);
			if (s.Length != 1)
			{
				throw new InvalidCastException();
			}
			return s[0];
		}

		/// <summary>
		/// Gets the value of a column as DateTime.
		/// </summary>
		public override DateTime GetDateTime(Int32 i)
		{
			return (DateTime) GetValue(i);
		}

		/// <summary>
		/// Returns a System.Data.DataTable that describes the column metadata of the DataReader.
		/// </summary>
		public override DataTable GetSchemaTable()
		{
			return _currentResultsetSchema = _currentResultsetSchema ?? GetResultsetSchema();
		}

		private DataTable GetResultsetSchema()
		{
			DataTable result = null;

			if (CurrentDescription.NumFields > 0)
			{
				result = new DataTable("SchemaTable");

				result.Columns.Add("ColumnName", typeof (string));
				result.Columns.Add("ColumnOrdinal", typeof (int));
				result.Columns.Add("ColumnSize", typeof (int));
				result.Columns.Add("NumericPrecision", typeof (int));
				result.Columns.Add("NumericScale", typeof (int));
				result.Columns.Add("IsUnique", typeof (bool));
				result.Columns.Add("IsKey", typeof (bool));
				result.Columns.Add("BaseCatalogName", typeof (string));
				result.Columns.Add("BaseColumnName", typeof (string));
				result.Columns.Add("BaseSchemaName", typeof (string));
				result.Columns.Add("BaseTableName", typeof (string));
				result.Columns.Add("DataType", typeof (Type));
				result.Columns.Add("AllowDBNull", typeof (bool));
				result.Columns.Add("ProviderType", typeof (string));
				result.Columns.Add("IsAliased", typeof (bool));
				result.Columns.Add("IsExpression", typeof (bool));
				result.Columns.Add("IsIdentity", typeof (bool));
				result.Columns.Add("IsAutoIncrement", typeof (bool));
				result.Columns.Add("IsRowVersion", typeof (bool));
				result.Columns.Add("IsHidden", typeof (bool));
				result.Columns.Add("IsLong", typeof (bool));
				result.Columns.Add("IsReadOnly", typeof (bool));

				if (_connector.BackendProtocolVersion == ProtocolVersion.Version2)
				{
					FillSchemaTable_v2(result);
				}
				else if (_connector.BackendProtocolVersion == ProtocolVersion.Version3)
				{
					FillSchemaTable_v3(result);
				}
			}

			return result;
		}

		private void FillSchemaTable_v2(DataTable schema)
		{
            List<string> keyList = (_behavior & CommandBehavior.KeyInfo) == CommandBehavior.KeyInfo
                                    ? new List<string>(GetPrimaryKeys(GetTableNameFromQuery()))
                                    : new List<string>();

			for (Int16 i = 0; i < CurrentDescription.NumFields; i++)
			{
				DataRow row = schema.NewRow();

				row["ColumnName"] = GetName(i);
				row["ColumnOrdinal"] = i + 1;
				if (CurrentDescription[i].TypeModifier != -1 && CurrentDescription[i].TypeInfo != null &&
				    (CurrentDescription[i].TypeInfo.Name == "varchar" || CurrentDescription[i].TypeInfo.Name == "bpchar"))
				{
					row["ColumnSize"] = CurrentDescription[i].TypeModifier - 4;
				}
				else if (CurrentDescription[i].TypeModifier != -1 && CurrentDescription[i].TypeInfo != null &&
				         (CurrentDescription[i].TypeInfo.Name == "bit" || CurrentDescription[i].TypeInfo.Name == "varbit"))
				{
					row["ColumnSize"] = CurrentDescription[i].TypeModifier;
				}
				else
				{
					row["ColumnSize"] = (int) CurrentDescription[i].TypeSize;
				}
				if (CurrentDescription[i].TypeModifier != -1 && CurrentDescription[i].TypeInfo != null &&
				    CurrentDescription[i].TypeInfo.Name == "numeric")
				{
					row["NumericPrecision"] = ((CurrentDescription[i].TypeModifier - 4) >> 16) & ushort.MaxValue;
					row["NumericScale"] = (CurrentDescription[i].TypeModifier - 4) & ushort.MaxValue;
				}
				else
				{
					row["NumericPrecision"] = 0;
					row["NumericScale"] = 0;
				}
				row["IsUnique"] = false;
				row["IsKey"] = IsKey(GetName(i), keyList);
				row["BaseCatalogName"] = "";
				row["BaseSchemaName"] = "";
				row["BaseTableName"] = "";
				row["BaseColumnName"] = GetName(i);
				row["DataType"] = GetFieldType(i);
				row["AllowDBNull"] = true;
                    // without other information, must allow dbnull on the client
				if (CurrentDescription[i].TypeInfo != null)
				{
					row["ProviderType"] = CurrentDescription[i].TypeInfo.Name;
				}
				row["IsAliased"] = false;
				row["IsExpression"] = false;
				row["IsIdentity"] = false;
				row["IsAutoIncrement"] = false;
				row["IsRowVersion"] = false;
				row["IsHidden"] = false;
				row["IsLong"] = false;
				row["IsReadOnly"] = false;

				schema.Rows.Add(row);
			}
		}

		private void FillSchemaTable_v3(DataTable schema)
		{
            Dictionary<long, Table> oidTableLookup = new Dictionary<long, Table>();
			KeyLookup keyLookup = new KeyLookup();
            // needs to be null because there is a difference
            // between an empty dictionary and not setting it
            // the default values will be different
			Dictionary<string, Column> columnLookup = null;

			if ((_behavior & CommandBehavior.KeyInfo) == CommandBehavior.KeyInfo)
			{
				List<int> tableOids = new List<int>();
				for (int i = 0; i != CurrentDescription.NumFields; ++i)
				{
					if (CurrentDescription[i].TableOID != 0 && !tableOids.Contains(CurrentDescription[i].TableOID))
					{
						tableOids.Add(CurrentDescription[i].TableOID);
					}
				}
				oidTableLookup = GetTablesFromOids(tableOids);

				if (oidTableLookup.Count == 1)
				{
					// only 1, but we can't index into the Dictionary
					foreach (int key in oidTableLookup.Keys)
					{
						keyLookup = GetKeys(key);
					}
				}

				columnLookup = GetColumns();
			}

			for (Int16 i = 0; i < CurrentDescription.NumFields; i++)
			{
				DataRow row = schema.NewRow();

				string baseColumnName = GetBaseColumnName(columnLookup, i);

				row["ColumnName"] = GetName(i);
				row["ColumnOrdinal"] = i + 1;
				if (CurrentDescription[i].TypeModifier != -1 && CurrentDescription[i].TypeInfo != null &&
				    (CurrentDescription[i].TypeInfo.Name == "varchar" || CurrentDescription[i].TypeInfo.Name == "bpchar"))
				{
					row["ColumnSize"] = CurrentDescription[i].TypeModifier - 4;
				}
				else if (CurrentDescription[i].TypeModifier != -1 && CurrentDescription[i].TypeInfo != null &&
				         (CurrentDescription[i].TypeInfo.Name == "bit" || CurrentDescription[i].TypeInfo.Name == "varbit"))
				{
					row["ColumnSize"] = CurrentDescription[i].TypeModifier;
				}
				else
				{
					row["ColumnSize"] = (int) CurrentDescription[i].TypeSize;
				}
				if (CurrentDescription[i].TypeModifier != -1 && CurrentDescription[i].TypeInfo != null &&
				    CurrentDescription[i].TypeInfo.Name == "numeric")
				{
					row["NumericPrecision"] = ((CurrentDescription[i].TypeModifier - 4) >> 16) & ushort.MaxValue;
					row["NumericScale"] = (CurrentDescription[i].TypeModifier - 4) & ushort.MaxValue;
				}
				else
				{
					row["NumericPrecision"] = 0;
					row["NumericScale"] = 0;
				}
				row["IsUnique"] = IsUnique(keyLookup, baseColumnName);
				row["IsKey"] = IsKey(keyLookup, baseColumnName);
				if (CurrentDescription[i].TableOID != 0 && oidTableLookup.ContainsKey(CurrentDescription[i].TableOID))
				{
					row["BaseCatalogName"] = oidTableLookup[CurrentDescription[i].TableOID].Catalog;
					row["BaseSchemaName"] = oidTableLookup[CurrentDescription[i].TableOID].Schema;
					row["BaseTableName"] = oidTableLookup[CurrentDescription[i].TableOID].Name;
				}
				else
				{
					row["BaseCatalogName"] = row["BaseSchemaName"] = row["BaseTableName"] = "";
				}
				row["BaseColumnName"] = baseColumnName;
				row["DataType"] = GetFieldType(i);
				row["AllowDBNull"] = IsNullable(columnLookup, i);
				if (CurrentDescription[i].TypeInfo != null)
				{
					row["ProviderType"] = CurrentDescription[i].TypeInfo.Name;
				}
				row["IsAliased"] = string.CompareOrdinal((string) row["ColumnName"], baseColumnName) != 0;
				row["IsExpression"] = false;
				row["IsIdentity"] = false;
				row["IsAutoIncrement"] = IsAutoIncrement(columnLookup, i);
				row["IsRowVersion"] = false;
				row["IsHidden"] = false;
				row["IsLong"] = false;
				row["IsReadOnly"] = false;

				schema.Rows.Add(row);
			}
		}


		private static Boolean IsKey(String ColumnName, IEnumerable<string> ListOfKeys)
		{
			foreach (String s in ListOfKeys)
			{
				if (s == ColumnName)
				{
					return true;
				}
			}

			return false;
		}

		private IEnumerable<string> GetPrimaryKeys(String tablename)
		{
			if (string.IsNullOrEmpty(tablename))
			{
				yield break;
			}

			String getPKColumns =
				"select a.attname from pg_catalog.pg_class ct, pg_catalog.pg_class ci, pg_catalog.pg_attribute a, pg_catalog.pg_index i  WHERE ct.oid=i.indrelid AND ci.oid=i.indexrelid  AND a.attrelid=ci.oid AND i.indisprimary AND ct.relname = :tablename";

			using (NpgsqlConnection metadataConn = _connection.Clone())
			{
				using (NpgsqlCommand c = new NpgsqlCommand(getPKColumns, metadataConn))
				{
					c.Parameters.Add(new NpgsqlParameter("tablename", NpgsqlDbType.Text));
					c.Parameters["tablename"].Value = tablename;


					using (NpgsqlDataReader dr = c.GetReader(CommandBehavior.SingleResult | CommandBehavior.SequentialAccess))
					{
						while (dr.Read())
						{
							yield return dr.GetString(0);
						}
					}
				}
			}
		}


		private static bool IsKey(KeyLookup keyLookup, string fieldName)

		{
			return keyLookup.primaryKey.Contains(fieldName);
		}

		private static bool IsUnique(KeyLookup keyLookup, string fieldName)
		{
			return keyLookup.uniqueColumns.Contains(fieldName);
		}

		private class KeyLookup
		{
			/// <summary>
			/// Contains the column names as the keys
			/// </summary>
			public readonly List<string> primaryKey = new List<string>();

			/// <summary>
			/// Contains all unique columns
			/// </summary>
			public readonly List<string> uniqueColumns = new List<string>();
		}

		private KeyLookup GetKeys(Int32 tableOid)
		{
			string getKeys =
				"select a.attname, ci.relname, i.indisprimary from pg_catalog.pg_class ct, pg_catalog.pg_class ci, pg_catalog.pg_attribute a, pg_catalog.pg_index i WHERE ct.oid=i.indrelid AND ci.oid=i.indexrelid AND a.attrelid=ci.oid AND i.indisunique AND ct.oid = :tableOid order by ci.relname";

			KeyLookup lookup = new KeyLookup();

			using (NpgsqlConnection metadataConn = _connection.Clone())
			{
				NpgsqlCommand c = new NpgsqlCommand(getKeys, metadataConn);
				c.Parameters.Add(new NpgsqlParameter("tableOid", NpgsqlDbType.Integer)).Value = tableOid;

				using (NpgsqlDataReader dr = c.GetReader(CommandBehavior.SequentialAccess | CommandBehavior.SingleResult))
				{
					string previousKeyName = null;
					string possiblyUniqueColumn = null;
					string columnName;
					string currentKeyName;
					// loop through adding any column that is primary to the primary key list
					// add any column that is the only column for that key to the unique list
					// unique here doesn't mean general unique constraint (with possibly multiple columns)
					// it means all values in this single column must be unique
					while (dr.Read())
					{
						columnName = dr.GetString(0);
						currentKeyName = dr.GetString(1);
						// if i.indisprimary
						if (dr.GetBoolean(2))
						{
							// add column name as part of the primary key
							lookup.primaryKey.Add(columnName);
						}
						if (currentKeyName != previousKeyName)
						{
							if (possiblyUniqueColumn != null)
							{
								lookup.uniqueColumns.Add(possiblyUniqueColumn);
							}
							possiblyUniqueColumn = columnName;
						}
						else
						{
							possiblyUniqueColumn = null;
						}
						previousKeyName = currentKeyName;
					}
					// if finished reading and have a possiblyUniqueColumn name that is
					// not null, then it is the name of a unique column
					if (possiblyUniqueColumn != null)
					{
						lookup.uniqueColumns.Add(possiblyUniqueColumn);
					}
					return lookup;
				}
			}
		}

		private Boolean IsNullable(Dictionary<string, Column> columnLookup, Int32 FieldIndex)
		{
			if (columnLookup == null || CurrentDescription[FieldIndex].TableOID == 0)
			{
				return true;
			}

			string lookupKey = string.Format("{0},{1}", CurrentDescription[FieldIndex].TableOID, CurrentDescription[FieldIndex].ColumnAttributeNumber);
			Column col = null;
			return columnLookup.TryGetValue(lookupKey, out col) ? !col.NotNull : true;
		}

		private string GetBaseColumnName(Dictionary<string, Column> columnLookup, Int32 FieldIndex)
		{
			if (columnLookup == null || CurrentDescription[FieldIndex].TableOID == 0)
			{
				return GetName(FieldIndex);
			}

			string lookupKey = string.Format("{0},{1}", CurrentDescription[FieldIndex].TableOID, CurrentDescription[FieldIndex].ColumnAttributeNumber);
			Column col = null;
			return columnLookup.TryGetValue(lookupKey, out col) ? col.Name : GetName(FieldIndex);
		}

		private bool IsAutoIncrement(Dictionary<string, Column> columnLookup, Int32 FieldIndex)
		{
			if (columnLookup == null || CurrentDescription[FieldIndex].TableOID == 0)
			{
				return false;
			}

			string lookupKey = string.Format("{0},{1}", CurrentDescription[FieldIndex].TableOID, CurrentDescription[FieldIndex].ColumnAttributeNumber);
			Column col = null;
			return
				columnLookup.TryGetValue(lookupKey, out col)
					? col.ColumnDefault is string && col.ColumnDefault.ToString().StartsWith("nextval(")
					: true;
		}


		///<summary>
		/// This methods parses the command text and tries to get the tablename
		/// from it.
		///</summary>
		private String GetTableNameFromQuery()
		{
			Int32 fromClauseIndex = _command.CommandText.ToLowerInvariant().IndexOf("from");

			String tableName = _command.CommandText.Substring(fromClauseIndex + 4).Trim();

			if (string.IsNullOrEmpty(tableName))// == String.Empty)
			{
				return String.Empty;
			}

			/*if (tableName.EndsWith("."));
                return String.Empty;
              */
			foreach (Char c in tableName.Substring(0, tableName.Length - 1))
			{
				if (!Char.IsLetterOrDigit(c) && c != '_' && c != '.')
				{
					return String.Empty;
				}
			}


			return tableName;
		}

		private struct Table
		{
			public readonly string Catalog;
			public readonly string Schema;
			public readonly string Name;
			public readonly long Id;

			public Table(IDataReader rdr)
			{
				Catalog = rdr.GetString(0);
				Schema = rdr.GetString(1);
				Name = rdr.GetString(2);
				Id = rdr.GetInt64(3);
			}
		}

		private Dictionary<long, Table> GetTablesFromOids(List<int> oids)
		{
			if (oids.Count == 0)
			{
				return new Dictionary<long, Table>(); //Empty collection is simpler than requiring tests for null;
			}

			// the column index is used to find data.
			// any changes to the order of the columns needs to be reflected in struct Tables
			StringBuilder sb =
				new StringBuilder(
					"SELECT current_database(), nc.nspname, c.relname, c.oid FROM pg_namespace nc, pg_class c WHERE c.relnamespace = nc.oid AND (c.relkind = 'r' OR c.relkind = 'v') AND c.oid IN (");
			bool first = true;
			foreach (int oid in oids)
			{
				if (!first)
				{
					sb.Append(',');
				}
				sb.Append(oid);
				first = false;
			}
			sb.Append(')');

			using (NpgsqlConnection connection = _connection.Clone())
			{
				using (NpgsqlCommand command = new NpgsqlCommand(sb.ToString(), connection))
				{
					using (NpgsqlDataReader reader = command.GetReader(CommandBehavior.SequentialAccess | CommandBehavior.SingleResult)
						)
					{
						Dictionary<long, Table> oidLookup = new Dictionary<long, Table>(oids.Count);
						int columnCount = reader.FieldCount;
						while (reader.Read())
						{
							Table t = new Table(reader);
							oidLookup.Add(t.Id, t);
						}
						return oidLookup;
					}
				}
			}
		}

		private class Column
		{
			public readonly string Name;
			public readonly bool NotNull;
			public readonly long TableId;
			public readonly short ColumnNum;
			public readonly object ColumnDefault;

			public string Key
			{
				get { return string.Format("{0},{1}", TableId, ColumnNum); }
			}

			public Column(IDataReader rdr)
			{
				Name = rdr.GetString(0);
				NotNull = rdr.GetBoolean(1);
				TableId = rdr.GetInt64(2);
				ColumnNum = rdr.GetInt16(3);
				ColumnDefault = rdr.GetValue(4);
			}
		}

		private Dictionary<string, Column> GetColumns()
		{
			StringBuilder sb = new StringBuilder();

			// the column index is used to find data.
			// any changes to the order of the columns needs to be reflected in struct Columns
			sb.Append(
				"SELECT a.attname AS column_name, a.attnotnull AS column_notnull, a.attrelid AS table_id, a.attnum AS column_num, d.adsrc as column_default");
			sb.Append(
				" FROM pg_attribute a LEFT OUTER JOIN pg_attrdef d ON a.attrelid = d.adrelid AND a.attnum = d.adnum WHERE a.attnum > 0 AND (");
			bool first = true;
			for (int i = 0; i < CurrentDescription.NumFields; ++i)
			{
				if (CurrentDescription[i].TableOID != 0)
				{
					if (!first)
					{
						sb.Append(" OR ");
					}
					sb.AppendFormat("(a.attrelid={0} AND a.attnum={1})", CurrentDescription[i].TableOID,
					                CurrentDescription[i].ColumnAttributeNumber);
					first = false;
				}
			}
			sb.Append(')');

			// if the loop ended without setting first to false, then there will be no results from the query
			if (first)
			{
				return null;
			}

			using (NpgsqlConnection connection = _connection.Clone())
			{
				using (NpgsqlCommand command = new NpgsqlCommand(sb.ToString(), connection))
				{
					using (NpgsqlDataReader reader = command.GetReader(CommandBehavior.SequentialAccess | CommandBehavior.SingleResult)
						)
					{
						Dictionary<string, Column> columnLookup = new Dictionary<string, Column>();
						while (reader.Read())
						{
							Column column = new Column(reader);
							columnLookup.Add(column.Key, column);
						}
						return columnLookup;
					}
				}
			}
		}

		public override IEnumerator GetEnumerator()
		{
			return new DbEnumerator(this);
		}
	}

	/// <summary>
	/// This is the primary implementation of NpgsqlDataReader. It is the one used in normal cases (where the 
	/// preload-reader option is not set in the connection string to resolve some potential backwards-compatibility
	/// issues), the only implementation used internally, and in cases where CachingDataReader is used, it is still
	/// used to do the actual "leg-work" of turning a response stream from the server into a datareader-style
	/// object - with CachingDataReader then filling it's cache from here.
	/// </summary>
	internal class ForwardsOnlyDataReader : NpgsqlDataReader, IStreamOwner
	{
		private readonly IEnumerator<IServerResponseObject> _dataEnumerator;
		private NpgsqlRowDescription _currentDescription;
		private NpgsqlRow _currentRow = null;
		private int? _recordsAffected = null;
		private int? _nextRecordsAffected;
		private long? _lastInsertOID = null;
		private long? _nextInsertOID = null;
		internal bool _cleanedUp = false;
		private readonly NpgsqlConnector.NotificationThreadBlock _threadBlock;
		private readonly bool _synchOnReadError; //maybe this should always be done?

		//Unfortunately we sometimes don't know we're going to be dealing with
		//a description until it comes when we look for a row or a message, and
		//we may also need test if we may have rows for HasRows before the first call
		//to Read(), so we need to be able to cache one of each.
		private NpgsqlRowDescription _pendingDescription = null;
		private NpgsqlRow _pendingRow = null;

		// Logging related values
		private static readonly String CLASSNAME = MethodBase.GetCurrentMethod().DeclaringType.Name;

		internal ForwardsOnlyDataReader(IEnumerable<IServerResponseObject> dataEnumeration, CommandBehavior behavior,
		                                NpgsqlCommand command, NpgsqlConnector.NotificationThreadBlock threadBlock,
		                                bool synchOnReadError)
			: base(command, behavior)
		{
			_dataEnumerator = dataEnumeration.GetEnumerator();
			_connector.CurrentReader = this;
			_threadBlock = threadBlock;
			_synchOnReadError = synchOnReadError;
			//DataReaders always start prepared to read from the first Resultset (if any).
			NextResult();
			UpdateOutputParameters();
		}

		internal override NpgsqlRowDescription CurrentDescription
		{
			get { return _currentDescription; }
		}

		private void UpdateOutputParameters()
		{
			if (CurrentDescription != null)
			{
				NpgsqlRow row = null;
				Queue<NpgsqlParameter> pending = new Queue<NpgsqlParameter>();
				List<int> taken = new List<int>();
				foreach (NpgsqlParameter p in _command.Parameters)
				{
					if (p.Direction == ParameterDirection.InputOutput || p.Direction == ParameterDirection.Output)
					{
						int idx = CurrentDescription.TryFieldIndex(p.CleanName);
						if (idx == -1)
						{
							pending.Enqueue(p);
						}
						else
						{
							if ((row = row ?? ParameterUpdateRow) == null)
							{
								return;
							}
							p.Value = row[idx];
							taken.Add(idx);
						}
					}
				}
				for (int i = 0; pending.Count != 0 && i != (row = row ?? ParameterUpdateRow).NumFields; ++i)
				{
					if (!taken.Contains(i))
					{
						pending.Dequeue().Value = row[i];
					}
				}
			}
		}

		// We always receive a ForwardsOnlyRow, but if we are not
		// doing SequentialAccess we want the flexibility of CachingRow,
		// so here we either return the ForwardsOnlyRow we received, or
		// build a CachingRow from it, as appropriate.
		private NpgsqlRow BuildRow(ForwardsOnlyRow fo)
		{
			if (fo == null)
			{
				return null;
			}
			else if ((_behavior & CommandBehavior.SequentialAccess) == CommandBehavior.SequentialAccess)
			{
				return fo;
			}
			else
			{
				return new CachingRow(fo);
			}
		}

		private NpgsqlRow ParameterUpdateRow
		{
			get
			{
				NpgsqlRow ret = CurrentRow ?? _pendingRow ?? GetNextRow(false);
				if (ret is ForwardsOnlyRow)
				{
					ret = _pendingRow = new CachingRow((ForwardsOnlyRow) ret);
				}
				return ret;
			}
		}

		/// <summary>
		/// Iterate through the objects returned through from the server.
		/// If it's a CompletedResponse the rowsaffected count is updated appropriately,
		/// and we iterate again, otherwise we return it (perhaps updating our cache of pending
		/// rows if appropriate).
		/// </summary>
		/// <returns>The next <see cref="IServerResponseObject"/> we will deal with.</returns>
		private IServerResponseObject GetNextResponseObject()
		{
			try
			{
				CurrentRow = null;
				if (_pendingRow != null)
				{
					_pendingRow.Dispose();
				}
				_pendingRow = null;
				while (_dataEnumerator.MoveNext())
				{
					IServerResponseObject respNext = _dataEnumerator.Current;
					if (respNext is CompletedResponse)
					{
						CompletedResponse cr = respNext as CompletedResponse;
						if (cr.RowsAffected.HasValue)
						{
							_nextRecordsAffected = (_nextRecordsAffected ?? 0) + cr.RowsAffected.Value;
						}
						_nextInsertOID = cr.LastInsertedOID ?? _nextInsertOID;
					}
					else if (respNext is ForwardsOnlyRow)
					{
						return _pendingRow = BuildRow((ForwardsOnlyRow) respNext);
					}
					else
					{
						return respNext;
					}
				}
				CleanUp(true);
				return null;
			}
			catch
			{
				CleanUp(true);
				if (_synchOnReadError) //Should we always do this?
				{
					// As per documentation:
					// "[...] When an error is detected while processing any extended-query message,
					// the backend issues ErrorResponse, then reads and discards messages until a
					// Sync is reached, then issues ReadyForQuery and returns to normal message processing.[...]"
					// So, send a sync command if we get any problems.

					_connector.Sync();
				}
				throw;
			}
		}

		/// <summary>
		/// Advances the data reader to the next result, when multiple result sets were returned by the PostgreSQL backend.
		/// </summary>
		/// <returns>True if the reader was advanced, otherwise false.</returns>
		private NpgsqlRowDescription GetNextRowDescription()
		{
			if ((_behavior & CommandBehavior.SingleResult) != 0 && CurrentDescription != null)
			{
				CleanUp(false);
				return null;
			}
			NpgsqlRowDescription rd = _pendingDescription;
			while (rd == null)
			{
				object objNext = GetNextResponseObject();
				if (objNext == null)
				{
					break;
				}
				if (objNext is NpgsqlRow)
				{
					(objNext as NpgsqlRow).Dispose();
				}

				rd = objNext as NpgsqlRowDescription;
			}

			_pendingDescription = null;
			
			// If there were records affected before,  keep track of their values.
                        if (_recordsAffected != null)
                            _recordsAffected += (_nextRecordsAffected ?? 0);
                        else
                            _recordsAffected = _nextRecordsAffected;
			
                        

			_nextRecordsAffected = null;
			_lastInsertOID = _nextInsertOID;
			_nextInsertOID = null;
			return rd;
		}

		private NpgsqlRow CurrentRow
		{
			get { return _currentRow; }
			set
			{
				if (_currentRow != null)
				{
					_currentRow.Dispose();
				}
				_currentRow = value;
			}
		}

		private NpgsqlRow GetNextRow(bool clearPending)
		{
			if (_pendingDescription != null)
			{
				return null;
			}
			if (((_behavior & CommandBehavior.SingleRow) != 0 && CurrentRow != null && _pendingDescription == null) ||
			    ((_behavior & CommandBehavior.SchemaOnly) != 0))
			{
				if (!clearPending)
				{
					return null;
				}
				//We should only have one row, and we've already had it. Move to end
				//of recordset.
				CurrentRow = null;
				for (object skip = GetNextResponseObject();
				     skip != null && (_pendingDescription = skip as NpgsqlRowDescription) == null;
				     skip = GetNextResponseObject())
				{
					if (skip is NpgsqlRow)
					{
						(skip as NpgsqlRow).Dispose();
					}
				}

				return null;
			}
			if (_pendingRow != null)
			{
				NpgsqlRow ret = _pendingRow;
				if (clearPending)
				{
					_pendingRow = null;
				}
				return ret;
			}
			CurrentRow = null;
			object objNext = GetNextResponseObject();
			if (clearPending)
			{
				_pendingRow = null;
			}
			if (objNext is NpgsqlRowDescription)
			{
				_pendingDescription = objNext as NpgsqlRowDescription;
				return null;
			}
			return objNext as NpgsqlRow;
		}

		internal override void CheckHaveRow()
		{
			if (CurrentRow == null)
			{
				throw new InvalidOperationException("Invalid attempt to read when no data is present.");
			}
		}

		/// <summary>
		/// Releases the resources used by the <see cref="Npgsql.NpgsqlCommand">NpgsqlCommand</see>.
		/// </summary>
		protected override void Dispose(bool disposing)
		{
			NpgsqlEventLog.LogMethodEnter(LogLevel.Debug, CLASSNAME, "Dispose");
			base.Dispose(disposing);
		}


		/// <summary>
		/// Gets the number of rows changed, inserted, or deleted by execution of the SQL statement.
		/// </summary>
		public override Int32 RecordsAffected
		{
			get
			{
				NpgsqlEventLog.LogPropertyGet(LogLevel.Debug, CLASSNAME, "RecordsAffected");
				return _recordsAffected ?? -1;
			}
		}

		internal override long? LastInsertedOID
		{
			get { return _lastInsertOID; }
		}

		/// <summary>
		/// Indicates if NpgsqlDatareader has rows to be read.
		/// </summary>
		public override Boolean HasRows
		{
			get { return GetNextRow(false) != null; }
		}

		private void CleanUp(bool finishedMessages)
		{
			lock (this)
			{
				if (_cleanedUp)
				{
					return;
				}
				_cleanedUp = true;
			}
			if (!finishedMessages)
			{
				do
				{
					if ((Thread.CurrentThread.ThreadState & (ThreadState.Aborted | ThreadState.AbortRequested)) != 0)
					{
						_connection.EmergencyClose();
						return;
					}
				}
				while (GetNextResponseObject() != null);
			}
			_connector.CurrentReader = null;
			_threadBlock.Dispose();
		}

		/// <summary>
		/// Closes the data reader object.
		/// </summary>
		public override void Close()
		{
			CleanUp(false);
			if ((_behavior & CommandBehavior.CloseConnection) == CommandBehavior.CloseConnection)
			{
				_connection.Close();
			}
			_isClosed = true;
			SendClosedEvent();
		}

		/// <summary>
		/// Advances the data reader to the next result, when multiple result sets were returned by the PostgreSQL backend.
		/// </summary>
		/// <returns>True if the reader was advanced, otherwise false.</returns>
		public override Boolean NextResult()
		{
            try
            {
                CurrentRow = null;
                _currentResultsetSchema = null;
                return (_currentDescription = GetNextRowDescription()) != null;
            }
            catch (System.IO.IOException ex)
            {
                throw _command.ClearPoolAndCreateException(ex);
            }
		}

		/// <summary>
		/// Advances the data reader to the next row.
		/// </summary>
		/// <returns>True if the reader was advanced, otherwise false.</returns>
		public override Boolean Read()
		{
            try
            {
                //CurrentRow = null;
                return (CurrentRow = GetNextRow(true)) != null;
            }
            catch (System.IO.IOException ex)
            {
                throw _command.ClearPoolAndCreateException(ex);
            }
		}

		/// <summary>
		/// Return the value of the column at index <param name="Index"></param>.
		/// </summary>
		public override Object GetValue(Int32 Index)
        {
            object providerValue = GetProviderSpecificValue(Index);
            NpgsqlBackendTypeInfo backendTypeInfo;
            if (_command.ExpectedTypes != null && _command.ExpectedTypes.Length > Index && _command.ExpectedTypes[Index] != null)
            {
                return ExpectedTypeConverter.ChangeType(providerValue, _command.ExpectedTypes[Index]);
            }                       
            else if ((_connection == null || !_connection.UseExtendedTypes) && TryGetTypeInfo(Index, out backendTypeInfo))
                return backendTypeInfo.ConvertToFrameworkType(providerValue);
            return providerValue;
        }

        public override object  GetProviderSpecificValue(int ordinal)
		{
			NpgsqlEventLog.LogMethodEnter(LogLevel.Debug, CLASSNAME, "GetValue");

            if (ordinal < 0 || ordinal >= CurrentDescription.NumFields)
			{
				throw new IndexOutOfRangeException("Column index out of range");
			}

			CheckHaveRow();

            object ret = CurrentRow[ordinal];
			if (ret is Exception)
			{
				throw (Exception) ret;
			}
			return ret;
		}

		/// <summary>
		/// Gets raw data from a column.
		/// </summary>
		public override Int64 GetBytes(Int32 i, Int64 fieldOffset, Byte[] buffer, Int32 bufferoffset, Int32 length)
		{
			return CurrentRow.GetBytes(i, fieldOffset, buffer, bufferoffset, length);
		}


		/// <summary>
		/// Gets raw data from a column.
		/// </summary>
		public override Int64 GetChars(Int32 i, Int64 fieldoffset, Char[] buffer, Int32 bufferoffset, Int32 length)
		{
			return CurrentRow.GetChars(i, fieldoffset, buffer, bufferoffset, length);
		}


		/// <summary>
		/// Report whether the value in a column is DBNull.
		/// </summary>
		public override Boolean IsDBNull(Int32 i)
		{
			CheckHaveRow();

			return CurrentRow.IsDBNull(i);
		}
	}

	/// <summary>
	/// <para>Provides an implementation of NpgsqlDataReader in which all data is pre-loaded into memory.
	/// This operates by first creating a ForwardsOnlyDataReader as usual, and then loading all of it's
	/// Rows into memory. There is a general principle that when there is a trade-off between a class design that
	/// is more efficient and/or scalable on the one hand and one that is less efficient but has more functionality
	/// (in this case the internal-only functionality of caching results) that one can build the less efficent class
	/// from the most efficient without significant extra loss in efficiency, but not the other way around. The relationship
	/// between ForwardsOnlyDataReader and CachingDataReader is an example of this).</para>
	/// <para>Since the interface presented to the user is still forwards-only, queues are used to
	/// store this information, so that dequeueing as we go we give the garbage collector the best opportunity
	/// possible to reclaim any memory that is no longer in use.</para>
	/// <para>ForwardsOnlyDataReader being used to actually
	/// obtain the information from the server means that the "leg-work" is still only done (and need only be
	/// maintained) in one place.</para>
	/// <para>This class exists to allow for certain potential backwards-compatibility issues to be resolved
	/// with little effort on the part of affected users. It is considerably less efficient than ForwardsOnlyDataReader
	/// and hence never used internally.</para>
	/// </summary>
	internal class CachingDataReader : NpgsqlDataReader
	{
		private class DataRow : List<object>
		{
		}

		private class ResultSet : Queue<DataRow>
		{
			private readonly int _recordsAffected;
			private readonly long? _lastInsertedOID;
			private readonly NpgsqlRowDescription _description;

			public ResultSet(NpgsqlRowDescription description, int recordsAffected, long? lastInsertedOID)
			{
				_description = description;
				_recordsAffected = recordsAffected;
				_lastInsertedOID = lastInsertedOID;
			}

			public NpgsqlRowDescription Description
			{
				get { return _description; }
			}

			public int RecordsAffected
			{
				get { return _recordsAffected; }
			}

			public long? LastInsertedOID
			{
				get { return _lastInsertedOID; }
			}
		}

		private readonly Queue<ResultSet> _results = new Queue<ResultSet>();
		private ResultSet _currentResult;
		private DataRow _currentRow;
		private int _lastRecordsAffected;

		public CachingDataReader(ForwardsOnlyDataReader reader, CommandBehavior behavior)
			: base(reader._command, behavior)
		{
			do
			{
				ResultSet rs = new ResultSet(reader.CurrentDescription, reader.RecordsAffected, reader.LastInsertedOID);
				while (reader.Read())
				{
					DataRow dr = new DataRow();
					for (int i = 0; i != reader.FieldCount; ++i)
					{
						dr.Add(reader.GetValue(i));
					}
					rs.Enqueue(dr);
				}
				_results.Enqueue(rs);
			}
			while (reader.NextResult());
			reader.Dispose();
			NextResult();
			UpdateOutputParameters();
		}

		private void UpdateOutputParameters()
		{
			if (CurrentDescription != null && _currentResult != null && _currentResult.Count != 0)
			{
				DataRow row = _currentResult.Peek();
				Queue<NpgsqlParameter> pending = new Queue<NpgsqlParameter>();
				List<int> taken = new List<int>();
				foreach (NpgsqlParameter p in _command.Parameters)
				{
					if (p.Direction == ParameterDirection.InputOutput || p.Direction == ParameterDirection.Output)
					{
						int idx = CurrentDescription.TryFieldIndex(p.CleanName);
						if (idx == -1)
						{
							pending.Enqueue(p);
						}
						else
						{
							p.Value = row[idx];
							taken.Add(idx);
						}
					}
				}
				for (int i = 0; pending.Count != 0 && i != CurrentDescription.NumFields; ++i)
				{
					if (!taken.Contains(i))
					{
						pending.Dequeue().Value = row[i];
					}
				}
			}
		}

		internal override long? LastInsertedOID
		{
			get { return _currentResult.LastInsertedOID; }
		}

		internal override NpgsqlRowDescription CurrentDescription
		{
			get { return _currentResult.Description; }
		}

		public override bool HasRows
		{
			get
			{
				if (_currentRow != null || _currentResult.Count != 0)
				{
					return true;
				}
				foreach (ResultSet rs in _results)
				{
					if (rs.Count != 0)
					{
						return true;
					}
				}
				return false;
			}
		}

		public override int RecordsAffected
		{
			get { return _lastRecordsAffected; }
		}

		internal override void CheckHaveRow()
		{
			if (_currentRow == null)
			{
				throw new InvalidOperationException("Invalid attempt to read when no data is present.");
			}
		}

		public override void Close()
		{
			if ((_behavior & CommandBehavior.CloseConnection) == CommandBehavior.CloseConnection)
			{
				_connection.Close();
			}
			_isClosed = true;
			SendClosedEvent();
		}

		public override long GetBytes(int i, long fieldOffset, byte[] buffer, int bufferoffset, int length)
		{
			byte[] source = (byte[]) this[i];
			if (buffer == null)
			{
				return source.Length - fieldOffset;
			}
			long finalLength = Math.Max(0, Math.Min(length, source.Length - fieldOffset));
			Array.Copy(source, fieldOffset, buffer, bufferoffset, finalLength);
			return finalLength;
		}

		public override long GetChars(int i, long fieldoffset, char[] buffer, int bufferoffset, int length)
		{
			string source = (string) this[i];
			if (buffer == null)
			{
				return source.Length - fieldoffset;
			}
			long finalLength = Math.Max(0, Math.Min(length, source.Length - fieldoffset));
			Array.Copy(source.ToCharArray(), fieldoffset, buffer, bufferoffset, finalLength);
			return finalLength;
		}

		public override Object GetValue(Int32 ordinal)
		{
			CheckHaveRow();
			if (ordinal < 0 || ordinal >= CurrentDescription.NumFields)
			{
				throw new IndexOutOfRangeException();
			}
			return _currentRow[ordinal];
		}

		public override bool IsDBNull(int ordinal)
		{
			CheckHaveRow();
			return GetValue(ordinal) == DBNull.Value;
		}

		public override bool NextResult()
		{
			if (_results.Count == 0)
			{
				_currentResult = null;
				return false;
			}
			_lastRecordsAffected = (_currentResult = _results.Dequeue()).RecordsAffected;
			return true;
		}

		public override bool Read()
		{
			if (_currentResult.Count == 0)
			{
				_currentRow = null;
				return false;
			}
			_currentRow = _currentResult.Dequeue();
			return true;
		}
	}
}
