/// <summary>
		/// Deletes all data associated to a document.
		/// </summary>
		/// <param name="document">The document.</param>
		/// <param name="state">A state object passed from the index (can be <c>null</c> or a <see cref="T:DbTransaction" />).</param>
		private void DeleteDataForDocument(IDocument document, object state) {
			// 1. Delete all data related to a document
			// 2. Delete all words that have no more mappings

			ICommandBuilder builder = GetCommandBuilder();
			QueryBuilder queryBuilder = new QueryBuilder(builder);

			string query = queryBuilder.DeleteFrom("IndexDocument");
			query = queryBuilder.Where(query, "Name", WhereOperator.Equals, "DocName");
			List<Parameter> parameters = new List<Parameter>(1);
			parameters.Add(new Parameter(ParameterType.String, "DocName", document.Name));

			string subQuery = queryBuilder.SelectFrom("IndexWordMapping", new string[] { "Word" });
			subQuery = queryBuilder.GroupBy(subQuery, new string[] { "Word" });
			string query2 = queryBuilder.DeleteFrom("IndexWord");
			query2 = queryBuilder.WhereNotInSubquery(query2, "IndexWord", "Id", subQuery);

			query = queryBuilder.AppendForBatch(query, query2);
            query = queryBuilder.BuildBatchCommand(query);
			DbCommand command = null;
			if(state != null) command = builder.GetCommand((DbTransaction)state, query, parameters);
			else command = builder.GetCommand(connString, query, parameters);

			// Close only if state is null
			ExecuteNonQuery(command, state == null);
		}
		/// <summary>
		/// Gets all the outgoing links stored.
		/// </summary>
		/// <returns>The outgoing links, in a dictionary in the form page-&gt;outgoing_links.</returns>
		public IDictionary<string, string[]> GetAllOutgoingLinks() {
			ICommandBuilder builder = GetCommandBuilder();
			QueryBuilder queryBuilder = new QueryBuilder(builder);

			// Explicit columns in order to allow usage of GROUP BY
			string query = queryBuilder.SelectFrom("OutgoingLink", new string[] { "Source", "Destination" });
			query = queryBuilder.GroupBy(query, new string[] { "Source", "Destination" });

			DbCommand command = builder.GetCommand(connString, query, new List<Parameter>());

			DbDataReader reader = ExecuteReader(command);

			if(reader != null) {
				Dictionary<string, string[]> result = new Dictionary<string, string[]>(100);

				string prevSource = "|||";
				string source = null;
				List<string> destinations = new List<string>(20);

				while(reader.Read()) {
					source = reader["Source"] as string;

					if(source != prevSource) {
						if(prevSource != "|||") {
							result.Add(prevSource, destinations.ToArray());
							destinations.Clear();
						}
					}

					prevSource = source;
					destinations.Add(reader["Destination"] as string);
				}

				result.Add(prevSource, destinations.ToArray());
				
				CloseReader(command, reader);

				return result;
			}
			else return null;
		}
		/// <summary>
		/// The the names of the pages with attachments.
		/// </summary>
		/// <returns>The names of the pages with attachments.</returns>
		public string[] GetPagesWithAttachments() {
			ICommandBuilder builder = GetCommandBuilder();
			QueryBuilder queryBuilder = new QueryBuilder(builder);

			string query = queryBuilder.SelectFrom("Attachment", new string[] { "Page" });
			query = queryBuilder.GroupBy(query, new[] { "Page" });
			query = queryBuilder.OrderBy(query, new[] { "Page" }, new[] { Ordering.Asc });

			DbCommand command = builder.GetCommand(connString, query, new List<Parameter>());

			DbDataReader reader = ExecuteReader(command);

			if(reader != null) {
				List<string> result = new List<string>(100);

				while(reader.Read()) {
					result.Add(reader["Page"] as string);
				}

				CloseReader(command, reader);

				return result.ToArray();
			}
			else return null;
		}