DeleteFrom() public method

Builds a DELETE FROM query.
public DeleteFrom ( string table ) : string
table string The table.
return string
Exemplo n.º 1
0
        /// <summary>
        /// Releases the lock.
        /// </summary>
        public override void Release()
        {
            ICommandBuilder builder     = _sqlStorageProviderUtility.GetCommandBuilder2();
            DbConnection    connection  = builder.GetConnection(_connString);
            DbTransaction   transaction = _sqlStorageProviderUtility.BeginTransaction(connection);

            QueryBuilder queryBuilder = new QueryBuilder(builder);

            string query = queryBuilder.DeleteFrom("SearchIndexLock");

            query = queryBuilder.Where(query, "Wiki", WhereOperator.Equals, "Wiki");
            query = queryBuilder.AndWhere(query, "Name", WhereOperator.Equals, "Name");

            List <Parameter> parameters = new List <Parameter>(2);

            parameters.Add(new Parameter(ParameterType.String, "Wiki", _wiki));
            parameters.Add(new Parameter(ParameterType.String, "Name", _name));

            DbCommand command = builder.GetCommand(transaction, query, parameters);

            int rows = _sqlStorageProviderUtility.ExecuteNonQuery(command, false);

            if (rows == 1)
            {
                _sqlStorageProviderUtility.CommitTransaction(transaction);
            }
            else
            {
                _sqlStorageProviderUtility.RollbackTransaction(transaction);
            }
        }
Exemplo n.º 2
0
        /// <summary>
        /// Obtains the lock.
        /// </summary>
        /// <returns><c>true</c> if the lock has been obtained, <c>false</c> otherwise.</returns>
        public override bool Obtain()
        {
            ICommandBuilder builder     = _sqlStorageProviderUtility.GetCommandBuilder2();
            DbConnection    connection  = builder.GetConnection(_connString);
            DbTransaction   transaction = _sqlStorageProviderUtility.BeginTransaction(connection);

            QueryBuilder queryBuilder = new QueryBuilder(builder);

            string query = queryBuilder.DeleteFrom("SearchIndexLock");

            query = queryBuilder.Where(query, "Wiki", WhereOperator.Equals, "Wiki");
            query = queryBuilder.AndWhere(query, "Name", WhereOperator.Equals, "Name");

            List <Parameter> parameters = new List <Parameter>(2);

            parameters.Add(new Parameter(ParameterType.String, "Wiki", _wiki));
            parameters.Add(new Parameter(ParameterType.String, "Name", _name));

            DbCommand command = builder.GetCommand(transaction, query, parameters);

            int rows = _sqlStorageProviderUtility.ExecuteNonQuery(command, false);

            if (rows != 0)
            {
                _sqlStorageProviderUtility.RollbackTransaction(transaction);
                return(false);                // Deletion command failed (0 is the only accepted value)
            }

            query = queryBuilder.InsertInto("SearchIndexLock",
                                            new string[] { "wiki", "Name", "Value" }, new string[] { "Wiki", "Name", "Value" });
            parameters = new List <Parameter>(3);
            parameters.Add(new Parameter(ParameterType.String, "Wiki", _wiki));
            parameters.Add(new Parameter(ParameterType.String, "Name", _name));
            parameters.Add(new Parameter(ParameterType.String, "Value", "locked"));

            command = builder.GetCommand(transaction, query, parameters);

            rows = _sqlStorageProviderUtility.ExecuteNonQuery(command, false);

            if (rows == 1)
            {
                _sqlStorageProviderUtility.CommitTransaction(transaction);
            }
            else
            {
                _sqlStorageProviderUtility.RollbackTransaction(transaction);
            }

            return(rows == 1);
        }
Exemplo n.º 3
0
        /// <summary>
        /// Deletes a file.
        /// </summary>
        /// <param name="name">The name of the file to be deleted.</param>
        public override void DeleteFile(string name)
        {
            ICommandBuilder builder     = _sqlStorageProviderUtility.GetCommandBuilder2();
            DbConnection    connection  = builder.GetConnection(_connString);
            DbTransaction   transaction = _sqlStorageProviderUtility.BeginTransaction(connection);

            if (!FileExists(transaction, name))
            {
                _sqlStorageProviderUtility.RollbackTransaction(transaction);
                return;
            }

            QueryBuilder queryBuilder = new QueryBuilder(builder);

            string query = queryBuilder.DeleteFrom("SearchIndex");

            query = queryBuilder.Where(query, "Wiki", WhereOperator.Equals, "Wiki");
            query = queryBuilder.AndWhere(query, "Name", WhereOperator.Equals, "Name");

            List <Parameter> parameters = new List <Parameter>(2);

            parameters.Add(new Parameter(ParameterType.String, "Wiki", _wiki));
            parameters.Add(new Parameter(ParameterType.String, "Name", name));

            DbCommand command = builder.GetCommand(transaction, query, parameters);

            int rows = _sqlStorageProviderUtility.ExecuteNonQuery(command, false);

            if (rows != 1)
            {
                _sqlStorageProviderUtility.RollbackTransaction(transaction);
            }
            else
            {
                _sqlStorageProviderUtility.CommitTransaction(transaction);

                if (_cacheDirectory.FileExists(name + ".blob"))
                {
                    _cacheDirectory.DeleteFile(name + ".blob");
                }

                if (_cacheDirectory.FileExists(name))
                {
                    _cacheDirectory.DeleteFile(name);
                }
            }
        }
Exemplo n.º 4
0
        /// <summary>
        /// Removes a plugin's assembly.
        /// </summary>
        /// <param name="connection">A database connection.</param>
        /// <param name="filename">The file name of the assembly to remove, such as "Assembly.dll".</param>
        /// <returns><c>true</c> if the assembly is removed, <c>false</c> otherwise.</returns>
        private bool DeletePluginAssembly(DbConnection connection, string filename)
        {
            ICommandBuilder builder      = GetCommandBuilder();
            QueryBuilder    queryBuilder = new QueryBuilder(builder);

            string query = queryBuilder.DeleteFrom("PluginAssembly");

            query = queryBuilder.Where(query, "Name", WhereOperator.Equals, "Name");

            List <Parameter> parameters = new List <Parameter>(1);

            parameters.Add(new Parameter(ParameterType.String, "Name", filename));

            DbCommand command = builder.GetCommand(connection, query, parameters);

            int rows = ExecuteNonQuery(command, false);

            return(rows == 1);
        }
        /// <summary>
        /// Deletes a File.
        /// </summary>
        /// <param name="fullName">The full name of the File.</param>
        /// <returns><c>true</c> if the File is deleted, <c>false</c> otherwise.</returns>
        /// <exception cref="ArgumentNullException">If <paramref name="fullName"/> is <c>null</c>.</exception>
        /// <exception cref="ArgumentException">If <paramref name="fullName"/> is empty or it does not exist.</exception>
        public bool DeleteFile(string fullName)
        {
            if(fullName == null) throw new ArgumentNullException("fullName");
            if(fullName.Length == 0) throw new ArgumentException("Full Name cannot be empty", "fullName");

            ICommandBuilder builder = GetCommandBuilder();
            DbConnection connection = builder.GetConnection(connString);
            DbTransaction transaction = BeginTransaction(connection);

            if(!FileExists(transaction, fullName)) {
                RollbackTransaction(transaction);
                throw new ArgumentException("File does not exist", "fullName");
            }

            QueryBuilder queryBuilder = new QueryBuilder(builder);

            string directory, filename;
            SplitFileFullName(fullName, out directory, out filename);

            string query = queryBuilder.DeleteFrom("File");
            query = queryBuilder.Where(query, "Name", WhereOperator.Equals, "Name");
            query = queryBuilder.AndWhere(query, "Directory", WhereOperator.Equals, "Directory");

            List<Parameter> parameters = new List<Parameter>(2);
            parameters.Add(new Parameter(ParameterType.String, "Name", filename));
            parameters.Add(new Parameter(ParameterType.String, "Directory", directory));

            DbCommand command = builder.GetCommand(transaction, query, parameters);

            int rows = ExecuteNonQuery(command, false);
            if(rows == 1) CommitTransaction(transaction);
            else RollbackTransaction(transaction);

            return rows == 1;
        }
        /// <summary>
        /// Removes a new Snippet.
        /// </summary>
        /// <param name="connection">A database connection.</param>
        /// <param name="name">The Name of the Snippet to remove.</param>
        /// <returns><c>true</c> if the snippet is removed, <c>false</c> otherwise.</returns>
        private bool RemoveSnippet(DbConnection connection, string name)
        {
            ICommandBuilder builder = GetCommandBuilder();
            QueryBuilder queryBuilder = new QueryBuilder(builder);

            string query = queryBuilder.DeleteFrom("Snippet");
            query = queryBuilder.Where(query, "Name", WhereOperator.Equals, "Name");

            List<Parameter> parameters = new List<Parameter>(1);
            parameters.Add(new Parameter(ParameterType.String, "Name", name));

            DbCommand command = builder.GetCommand(connection, query, parameters);

            int rows = ExecuteNonQuery(command, false);

            return rows == 1;
        }
        /// <summary>
        /// Removes a Message.
        /// </summary>
        /// <param name="transaction">A database transaction.</param>
        /// <param name="page">The Page.</param>
        /// <param name="id">The ID of the Message to remove.</param>
        /// <param name="removeReplies">A value specifying whether or not to remove the replies.</param>
        /// <returns>True if the Message is removed successfully.</returns>
        private bool RemoveMessage(DbTransaction transaction, PageInfo page, int id, bool removeReplies)
        {
            string nspace, name;
            NameTools.ExpandFullName(page.FullName, out nspace, out name);
            if(nspace == null) nspace = "";

            Message[] messages = GetMessages(transaction, page);
            if(messages == null) return false;
            Message message = FindMessage(messages, id);
            if(message == null) return false;
            Message parent = FindAnchestor(messages, id);
            int parentId = parent != null ? parent.ID : -1;

            UnindexMessage(page, message.ID, message.Subject, message.DateTime, message.Body, transaction);

            if(removeReplies) {
                // Recursively remove all replies BEFORE removing parent (depth-first)
                foreach(Message reply in message.Replies) {
                    if(!RemoveMessage(transaction, page, reply.ID, true)) return false;
                }
            }

            // Remove this message
            ICommandBuilder builder = GetCommandBuilder();
            QueryBuilder queryBuilder = new QueryBuilder(builder);

            string query = queryBuilder.DeleteFrom("Message");
            query = queryBuilder.Where(query, "Page", WhereOperator.Equals, "Page");
            query = queryBuilder.AndWhere(query, "Namespace", WhereOperator.Equals, "Namespace");
            query = queryBuilder.AndWhere(query, "Id", WhereOperator.Equals, "Id");

            List<Parameter> parameters = new List<Parameter>(3);
            parameters.Add(new Parameter(ParameterType.String, "Page", name));
            parameters.Add(new Parameter(ParameterType.String, "Namespace", nspace));
            parameters.Add(new Parameter(ParameterType.Int16, "Id", (short)id));

            DbCommand command = builder.GetCommand(transaction, query, parameters);

            int rows = ExecuteNonQuery(command, false);

            if(!removeReplies && rows == 1) {
                // Update replies' parent id

                query = queryBuilder.Update("Message", new string[] { "Parent" }, new string[] { "NewParent" });
                query = queryBuilder.Where(query, "Page", WhereOperator.Equals, "Page");
                query = queryBuilder.AndWhere(query, "Namespace", WhereOperator.Equals, "Namespace");
                query = queryBuilder.AndWhere(query, "Parent", WhereOperator.Equals, "OldParent");

                parameters = new List<Parameter>(4);
                if(parentId != -1) parameters.Add(new Parameter(ParameterType.Int16, "NewParent", parentId));
                else parameters.Add(new Parameter(ParameterType.Int16, "NewParent", DBNull.Value));
                parameters.Add(new Parameter(ParameterType.String, "Page", name));
                parameters.Add(new Parameter(ParameterType.String, "Namespace", nspace));
                parameters.Add(new Parameter(ParameterType.Int16, "OldParent", (short)id));

                command = builder.GetCommand(transaction, query, parameters);

                rows = ExecuteNonQuery(command, false);
            }

            return rows > 0;
        }
        /// <summary>
        /// Binds a Page with one or more Categories.
        /// </summary>
        /// <param name="connection">A database connection.</param>
        /// <param name="page">The Page to bind.</param>
        /// <param name="categories">The Categories to bind the Page with.</param>
        /// <returns>True if the binding succeeded.</returns>
        /// <remarks>After a successful operation, the Page is bound with all and only the categories passed as argument.</remarks>
        private bool RebindPage(DbConnection connection, PageInfo page, string[] categories)
        {
            string nspace, name;
            NameTools.ExpandFullName(page.FullName, out nspace, out name);
            if(nspace == null) nspace = "";

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

            string query = queryBuilder.DeleteFrom("CategoryBinding");
            query = queryBuilder.Where(query, "Page", WhereOperator.Equals, "Page");
            query = queryBuilder.AndWhere(query, "Namespace", WhereOperator.Equals, "Namespace");

            List<Parameter> parameters = new List<Parameter>(2);
            parameters.Add(new Parameter(ParameterType.String, "Page", name));
            parameters.Add(new Parameter(ParameterType.String, "Namespace", nspace));

            DbCommand command = builder.GetCommand(connection, query, parameters);

            int rows = ExecuteNonQuery(command, false);

            if(rows < 0) return false;

            if(categories.Length > 0) {
                string finalQuery = "";
                parameters = new List<Parameter>(categories.Length * 3);
                int count = 0;
                string countString;

                foreach(string cat in categories) {
                    countString = count.ToString();

                    query = queryBuilder.InsertInto("CategoryBinding", new string[] { "Namespace", "Category", "Page" },
                        new string[] { "Namespace" + countString, "Category" + countString, "Page" + countString });
                    finalQuery = queryBuilder.AppendForBatch(finalQuery, query);

                    parameters.Add(new Parameter(ParameterType.String, "Namespace" + countString, nspace));
                    parameters.Add(new Parameter(ParameterType.String, "Category" + countString, NameTools.GetLocalName(cat)));
                    parameters.Add(new Parameter(ParameterType.String, "Page" + countString, name));

                    count++;
                }

                command = builder.GetCommand(connection, finalQuery, parameters);

                rows = ExecuteNonQuery(command, false);

                return rows == categories.Length;
            }
            else return true;
        }
        /// <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);

            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>
        /// Removes a plugin's assembly.
        /// </summary>
        /// <param name="transaction">A database transaction.</param>
        /// <param name="filename">The file name of the assembly to remove, such as "Assembly.dll".</param>
        /// <returns><c>true</c> if the assembly is removed, <c>false</c> otherwise.</returns>
        private bool DeletePluginAssembly(DbTransaction transaction, string filename)
        {
            ICommandBuilder builder = GetCommandBuilder();
            QueryBuilder queryBuilder = new QueryBuilder(builder);

            string query = queryBuilder.DeleteFrom("PluginAssembly");
            query = queryBuilder.Where(query, "Name", WhereOperator.Equals, "Name");

            List<Parameter> parameters = new List<Parameter>(1);
            parameters.Add(new Parameter(ParameterType.String, "Name", filename));

            DbCommand command = builder.GetCommand(transaction, query, parameters);

            int rows = ExecuteNonQuery(command, false);

            return rows == 1;
        }
        /// <summary>
        /// Deletes some ACL entries.
        /// </summary>
        /// <param name="entries">The entries to delete.</param>
        /// <returns><c>true</c> if one or more entries were deleted, <c>false</c> otherwise.</returns>
        private bool DeleteEntries(AclEntry[] entries)
        {
            ICommandBuilder builder = GetCommandBuilder();
            DbConnection connection = builder.GetConnection(connString);
            DbTransaction transaction = BeginTransaction(connection);

            QueryBuilder queryBuilder = new QueryBuilder(builder);

            foreach(AclEntry entry in entries) {
                string query = queryBuilder.DeleteFrom("AclEntry");
                query = queryBuilder.Where(query, "Resource", WhereOperator.Equals, "Resource");
                query = queryBuilder.AndWhere(query, "Action", WhereOperator.Equals, "Action");
                query = queryBuilder.AndWhere(query, "Subject", WhereOperator.Equals, "Subject");

                List<Parameter> parameters = new List<Parameter>(3);
                parameters.Add(new Parameter(ParameterType.String, "Resource", entry.Resource));
                parameters.Add(new Parameter(ParameterType.String, "Action", entry.Action));
                parameters.Add(new Parameter(ParameterType.String, "Subject", entry.Subject));

                DbCommand command = builder.GetCommand(transaction, query, parameters);

                if(ExecuteNonQuery(command, false) <= 0) {
                    RollbackTransaction(transaction);
                    return false;
                }
            }

            CommitTransaction(transaction);

            return true;
        }
        /// <summary>
        /// Cuts the recent changes if necessary.
        /// </summary>
        private void CutRecentChangesIfNecessary()
        {
            ICommandBuilder builder = GetCommandBuilder();
            DbConnection connection = builder.GetConnection(connString);
            DbTransaction transaction = BeginTransaction(connection);

            QueryBuilder queryBuilder = new QueryBuilder(builder);

            string query = queryBuilder.SelectCountFrom("RecentChange");

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

            int rows = ExecuteScalar<int>(command, -1, false);

            int maxChanges = int.Parse(host.GetSettingValue(SettingName.MaxRecentChanges));

            if(rows > maxChanges) {
                // Remove 10% of old changes to avoid 1-by-1 deletion every time a change is made
                int entriesToDelete = maxChanges / 10;
                if(entriesToDelete > rows) entriesToDelete = rows;
                //entriesToDelete += entriesToDelete / 10;

                // This code is not optimized, but it surely works in most DBMS
                query = queryBuilder.SelectFrom("RecentChange", new string[] { "Id" });
                query = queryBuilder.OrderBy(query, new string[] { "Id" }, new Ordering[] { Ordering.Asc });

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

                DbDataReader reader = ExecuteReader(command);

                List<int> ids = new List<int>(entriesToDelete);

                if(reader != null) {
                    while(reader.Read() && ids.Count < entriesToDelete) {
                        ids.Add((int)reader["Id"]);
                    }

                    CloseReader(reader);
                }

                if(ids.Count > 0) {
                    // Given that the IDs to delete can be many, the query is split in many chunks, each one deleting 50 items
                    // This works-around the problem of too many parameters in a RPC call of SQL Server
                    // See also CutLog

                    for(int chunk = 0; chunk <= ids.Count / MaxParametersInQuery; chunk++) {
                        query = queryBuilder.DeleteFrom("RecentChange");
                        List<string> parms = new List<string>(MaxParametersInQuery);
                        List<Parameter> parameters = new List<Parameter>(MaxParametersInQuery);

                        for(int i = chunk * MaxParametersInQuery; i < Math.Min(ids.Count, (chunk + 1) * MaxParametersInQuery); i++) {
                            parms.Add("P" + i.ToString());
                            parameters.Add(new Parameter(ParameterType.Int32, parms[parms.Count - 1], ids[i]));
                        }

                        query = queryBuilder.WhereIn(query, "Id", parms.ToArray());

                        command = builder.GetCommand(transaction, query, parameters);

                        if(ExecuteNonQuery(command, false) < 0) {
                            RollbackTransaction(transaction);
                            return;
                        }
                    }
                }
            }

            CommitTransaction(transaction);
        }
Exemplo n.º 13
0
        /// <summary>
        /// Reduces the size of the Log to the specified size (or less).
        /// </summary>
        /// <param name="size">The size to shrink the log to (in bytes).</param>
        private void CutLog(int size)
        {
            ICommandBuilder builder     = GetCommandBuilder();
            DbConnection    connection  = builder.GetConnection(connString);
            DbTransaction   transaction = BeginTransaction(connection);

            QueryBuilder queryBuilder = new QueryBuilder(builder);

            string query = queryBuilder.SelectCountFrom("Log");

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

            int rows = ExecuteScalar <int>(command, -1, false);

            if (rows == -1)
            {
                RollbackTransaction(transaction);
                return;
            }

            int estimatedSize = rows * EstimatedLogEntrySize;

            if (size < estimatedSize)
            {
                int difference      = estimatedSize - size;
                int entriesToDelete = difference / EstimatedLogEntrySize;
                // Add 10% to avoid 1-by-1 deletion when adding new entries
                entriesToDelete += entriesToDelete / 10;

                if (entriesToDelete > 0)
                {
                    // This code is not optimized, but it surely works in most DBMS
                    query = queryBuilder.SelectFrom("Log", new string[] { "Id" });
                    query = queryBuilder.OrderBy(query, new string[] { "Id" }, new Ordering[] { Ordering.Asc });

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

                    DbDataReader reader = ExecuteReader(command);

                    List <int> ids = new List <int>(entriesToDelete);

                    if (reader != null)
                    {
                        while (reader.Read() && ids.Count < entriesToDelete)
                        {
                            ids.Add((int)reader["Id"]);
                        }

                        CloseReader(reader);
                    }

                    if (ids.Count > 0)
                    {
                        // Given that the IDs to delete can be many, the query is split in many chunks, each one deleting 50 items
                        // This works-around the problem of too many parameters in a RPC call of SQL Server
                        // See also CutRecentChangesIfNecessary

                        for (int chunk = 0; chunk <= ids.Count / MaxParametersInQuery; chunk++)
                        {
                            query = queryBuilder.DeleteFrom("Log");
                            List <string>    parms      = new List <string>(MaxParametersInQuery);
                            List <Parameter> parameters = new List <Parameter>(MaxParametersInQuery);

                            for (int i = chunk * MaxParametersInQuery; i < Math.Min(ids.Count, (chunk + 1) * MaxParametersInQuery); i++)
                            {
                                parms.Add("P" + i.ToString());
                                parameters.Add(new Parameter(ParameterType.Int32, parms[parms.Count - 1], ids[i]));
                            }

                            query = queryBuilder.WhereIn(query, "Id", parms.ToArray());

                            command = builder.GetCommand(transaction, query, parameters);

                            if (ExecuteNonQuery(command, false) < 0)
                            {
                                RollbackTransaction(transaction);
                                return;
                            }
                        }
                    }

                    CommitTransaction(transaction);
                }
            }
        }
Exemplo n.º 14
0
        /// <summary>
        /// Stores the value of a Setting.
        /// </summary>
        /// <param name="name">The name of the Setting.</param>
        /// <param name="value">The value of the Setting. Value cannot contain CR and LF characters, which will be removed.</param>
        /// <returns>True if the Setting is stored, false otherwise.</returns>
        /// <remarks>This method stores the Value immediately.</remarks>
        public bool SetSetting(string name, string value)
        {
            if (name == null)
            {
                throw new ArgumentNullException("name");
            }
            if (name.Length == 0)
            {
                throw new ArgumentException("Name cannot be empty", "name");
            }

            // 1. Delete old value, if any
            // 2. Store new value

            // Nulls are converted to empty strings
            if (value == null)
            {
                value = "";
            }

            ICommandBuilder builder     = GetCommandBuilder();
            DbConnection    connection  = builder.GetConnection(connString);
            DbTransaction   transaction = BeginTransaction(connection);

            QueryBuilder queryBuilder = new QueryBuilder(builder);

            string query = queryBuilder.DeleteFrom("GlobalSetting");

            query = queryBuilder.Where(query, "Name", WhereOperator.Equals, "Name");

            List <Parameter> parameters = new List <Parameter>(1);

            parameters.Add(new Parameter(ParameterType.String, "Name", name));

            DbCommand command = builder.GetCommand(transaction, query, parameters);

            int rows = ExecuteNonQuery(command, false);

            if (rows == -1)
            {
                RollbackTransaction(transaction);
                return(false);                // Deletion command failed (0-1 are OK)
            }

            query = queryBuilder.InsertInto("GlobalSetting",
                                            new string[] { "Name", "Value" }, new string[] { "Name", "Value" });
            parameters = new List <Parameter>(2);
            parameters.Add(new Parameter(ParameterType.String, "Name", name));
            parameters.Add(new Parameter(ParameterType.String, "Value", value));

            command = builder.GetCommand(transaction, query, parameters);

            rows = ExecuteNonQuery(command, false);

            if (rows == 1)
            {
                CommitTransaction(transaction);
            }
            else
            {
                RollbackTransaction(transaction);
            }

            return(rows == 1);
        }
        /// <summary>
        /// Removes a user group.
        /// </summary>
        /// <param name="group">The group to remove.</param>
        /// <returns><c>true</c> if the group is removed, <c>false</c> otherwise.</returns>
        /// <exception cref="ArgumentNullException">If <b>group</b> is <c>null</c>.</exception>
        public bool RemoveUserGroup(UserGroup group)
        {
            if(group == null) throw new ArgumentNullException("group");

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

            string query = queryBuilder.DeleteFrom("UserGroup");
            query = queryBuilder.Where(query, "Name", WhereOperator.Equals, "Name");

            List<Parameter> parameters = new List<Parameter>(1);
            parameters.Add(new Parameter(ParameterType.String, "Name", group.Name));

            DbCommand command = builder.GetCommand(connString, query, parameters);

            int rows = ExecuteNonQuery(command);

            return rows == 1;
        }
        /// <summary>
        /// Removes the user group membership for a user.
        /// </summary>
        /// <param name="transaction">A database transaction.</param>
        /// <param name="username">The username.</param>
        private void RemoveUserGroupMembership(DbTransaction transaction, string username)
        {
            ICommandBuilder builder = GetCommandBuilder();
            QueryBuilder queryBuilder = new QueryBuilder(builder);

            string query = queryBuilder.DeleteFrom("UserGroupMembership");
            query = queryBuilder.Where(query, "User", WhereOperator.Equals, "Username");

            List<Parameter> parameters = new List<Parameter>(1);
            parameters.Add(new Parameter(ParameterType.String, "Username", username));

            DbCommand command = builder.GetCommand(transaction, query, parameters);

            ExecuteNonQuery(command, false);
        }
        /// <summary>
        /// Deletes a revision of a page content.
        /// </summary>
        /// <param name="connection">A database connection.</param>
        /// <param name="page">The page.</param>
        /// <param name="revision">The revision.</param>
        /// <returns><c>true</c> if the content ir deleted, <c>false</c> otherwise.</returns>
        private bool DeleteContent(DbConnection connection, PageInfo page, int revision)
        {
            string name, nspace;
            NameTools.ExpandFullName(page.FullName, out nspace, out name);
            if(nspace == null) nspace = "";

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

            string query = queryBuilder.DeleteFrom("PageContent");
            query = queryBuilder.Where(query, "Page", WhereOperator.Equals, "Page");
            query = queryBuilder.AndWhere(query, "Namespace", WhereOperator.Equals, "Namespace");
            query = queryBuilder.AndWhere(query, "Revision", WhereOperator.Equals, "Revision");

            List<Parameter> parameters = new List<Parameter>(3);
            parameters.Add(new Parameter(ParameterType.String, "Page", name));
            parameters.Add(new Parameter(ParameterType.String, "Namespace", nspace));
            parameters.Add(new Parameter(ParameterType.String, "Revision", revision));

            DbCommand command = builder.GetCommand(connection, query, parameters);

            int rows = ExecuteNonQuery(command, false);

            return rows > 0;
        }
        /// <summary>
        /// Deletes the outgoing links of a page and all the target links that include the page.
        /// </summary>
        /// <param name="page">The full name of the page.</param>
        /// <returns><c>true</c> if the links are deleted, <c>false</c> otherwise.</returns>
        /// <exception cref="ArgumentNullException">If <b>page</b> is <c>null</c>.</exception>
        /// <exception cref="ArgumentException">If <b>page</b> is empty.</exception>
        public bool DeleteOutgoingLinks(string page)
        {
            if(page == null) throw new ArgumentNullException("page");
            if(page.Length == 0) throw new ArgumentException("Page cannot be empty", "page");

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

            string query = queryBuilder.DeleteFrom("OutgoingLink");
            query = queryBuilder.Where(query, "Source", WhereOperator.Equals, "Source");
            query = queryBuilder.OrWhere(query, "Destination", WhereOperator.Equals, "Destination");

            List<Parameter> parameters = new List<Parameter>(2);
            parameters.Add(new Parameter(ParameterType.String, "Source", page));
            parameters.Add(new Parameter(ParameterType.String, "Destination", page));

            DbCommand command = builder.GetCommand(connString, query, parameters);

            int rows = ExecuteNonQuery(command);

            return rows > 0;
        }
        /// <summary>
        /// Removes all messages for a page and stores the new messages.
        /// </summary>
        /// <param name="page">The page.</param>
        /// <param name="messages">The new messages to store.</param>
        /// <returns><c>true</c> if the messages are stored, <c>false</c> otherwise.</returns>
        /// <exception cref="ArgumentNullException">If <paramref name="page"/> or <paramref name="messages"/> are <c>null</c>.</exception>
        public bool BulkStoreMessages(PageInfo page, Message[] messages)
        {
            if(page == null) throw new ArgumentNullException("page");
            if(messages == null) throw new ArgumentNullException("messages");

            ICommandBuilder builder = GetCommandBuilder();
            DbConnection connection = builder.GetConnection(connString);
            DbTransaction transaction = BeginTransaction(connection);

            if(GetPage(transaction, page.FullName) == null) {
                RollbackTransaction(transaction);
                return false;
            }

            foreach(Message msg in GetMessages(transaction, page)) {
                UnindexMessageTree(page, msg, transaction);
            }

            string nspace, name;
            NameTools.ExpandFullName(page.FullName, out nspace, out name);
            if(nspace == null) nspace = "";

            QueryBuilder queryBuilder = new QueryBuilder(builder);

            string query = queryBuilder.DeleteFrom("Message");
            query = queryBuilder.Where(query, "Page", WhereOperator.Equals, "Page");
            query = queryBuilder.AndWhere(query, "Namespace", WhereOperator.Equals, "Namespace");

            List<Parameter> parameters = new List<Parameter>(2);
            parameters.Add(new Parameter(ParameterType.String, "Page", name));
            parameters.Add(new Parameter(ParameterType.String, "Namespace", nspace));

            DbCommand command = builder.GetCommand(transaction, query, parameters);

            ExecuteNonQuery(command, false);

            List<Message> allMessages;
            List<int> parents;

            UnTreeMessages(messages, out allMessages, out parents, -1);

            string finalQuery = "";
            int count = 1;
            string countString;
            parameters = new List<Parameter>(MaxStatementsInBatch * 8);

            int rowsDone = 0;

            for(int i = 0; i < allMessages.Count; i++) {
                // Execute the batch in smaller chunks

                Message msg = allMessages[i];
                int parent = parents[i];

                countString = count.ToString();

                query = queryBuilder.InsertInto("Message", new string[] { "Page", "Namespace", "Id", "Parent", "Username", "Subject", "DateTime", "Body" },
                    new string[] { "Page" + countString, "Namespace" + countString, "Id" + countString, "Parent" + countString, "Username" + countString, "Subject" + countString, "DateTime" + countString, "Body" + countString });

                parameters.Add(new Parameter(ParameterType.String, "Page" + countString, name));
                parameters.Add(new Parameter(ParameterType.String, "Namespace" + countString, nspace));
                parameters.Add(new Parameter(ParameterType.Int16, "Id" + countString, (short)msg.ID));
                if(parent != -1) parameters.Add(new Parameter(ParameterType.Int16, "Parent" + countString, parent));
                else parameters.Add(new Parameter(ParameterType.Int16, "Parent" + countString, DBNull.Value));
                parameters.Add(new Parameter(ParameterType.String, "Username" + countString, msg.Username));
                parameters.Add(new Parameter(ParameterType.String, "Subject" + countString, msg.Subject));
                parameters.Add(new Parameter(ParameterType.DateTime, "DateTime" + countString, msg.DateTime));
                parameters.Add(new Parameter(ParameterType.String, "Body" + countString, msg.Body));

                finalQuery = queryBuilder.AppendForBatch(finalQuery, query);

                count++;

                if(count == MaxStatementsInBatch) {
                    command = builder.GetCommand(transaction, finalQuery, parameters);

                    rowsDone += ExecuteNonQuery(command, false);

                    finalQuery = "";
                    count = 1;
                    parameters.Clear();
                }
            }

            if(finalQuery.Length > 0) {
                command = builder.GetCommand(transaction, finalQuery, parameters);

                rowsDone += ExecuteNonQuery(command, false);
            }

            if(rowsDone == allMessages.Count) {
                foreach(Message msg in messages) {
                    IndexMessageTree(page, msg, transaction);
                }
                CommitTransaction(transaction);
                return true;
            }
            else {
                RollbackTransaction(transaction);
                return false;
            }
        }
        /// <summary>
        /// Sets a meta-data items' content.
        /// </summary>
        /// <param name="item">The item.</param>
        /// <param name="tag">The tag that specifies the context (usually the namespace).</param>
        /// <param name="content">The content.</param>
        /// <returns><c>true</c> if the content is set, <c>false</c> otherwise.</returns>
        public bool SetMetaDataItem(MetaDataItem item, string tag, string content)
        {
            if(tag == null) tag = "";
            if(content == null) content = "";

            // 1. Delete old value, if any
            // 2. Store new value

            ICommandBuilder builder = GetCommandBuilder();
            DbConnection connection = builder.GetConnection(connString);
            DbTransaction transaction = BeginTransaction(connection);

            QueryBuilder queryBuilder = new QueryBuilder(builder);

            string query = queryBuilder.DeleteFrom("MetaDataItem");
            query = queryBuilder.Where(query, "Name", WhereOperator.Equals, "Name");
            query = queryBuilder.AndWhere(query, "Tag", WhereOperator.Equals, "Tag");

            List<Parameter> parameters = new List<Parameter>(2);
            parameters.Add(new Parameter(ParameterType.String, "Name", item.ToString()));
            parameters.Add(new Parameter(ParameterType.String, "Tag", tag));

            DbCommand command = builder.GetCommand(transaction, query, parameters);

            int rows = ExecuteNonQuery(command, false);

            if(rows == -1) {
                RollbackTransaction(transaction);
                return false;
            }

            query = queryBuilder.InsertInto("MetaDataItem", new string[] { "Name", "Tag", "Data" }, new string[] { "Name", "Tag", "Content" });

            parameters = new List<Parameter>(3);
            parameters.Add(new Parameter(ParameterType.String, "Name", item.ToString()));
            parameters.Add(new Parameter(ParameterType.String, "Tag", tag));
            parameters.Add(new Parameter(ParameterType.String, "Content", content));

            command = builder.GetCommand(transaction, query, parameters);

            rows = ExecuteNonQuery(command, false);

            if(rows == 1) CommitTransaction(transaction);
            else RollbackTransaction(transaction);

            return rows == 1;
        }
        /// <summary>
        /// Removes a Category.
        /// </summary>
        /// <param name="transaction">A database transaction.</param>
        /// <param name="category">The Category to remove.</param>
        /// <returns>True if the Category has been removed successfully.</returns>
        private bool RemoveCategory(DbTransaction transaction, CategoryInfo category)
        {
            string nspace = null;
            string name = null;
            NameTools.ExpandFullName(category.FullName, out nspace, out name);
            if(nspace == null) nspace = "";

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

            string query = queryBuilder.DeleteFrom("Category");
            query = queryBuilder.Where(query, "Name", WhereOperator.Equals, "Name");
            query = queryBuilder.AndWhere(query, "Namespace", WhereOperator.Equals, "Namespace");

            List<Parameter> parameters = new List<Parameter>(2);
            parameters.Add(new Parameter(ParameterType.String, "Name", name));
            parameters.Add(new Parameter(ParameterType.String, "Namespace", nspace));

            DbCommand command = builder.GetCommand(transaction, query, parameters);

            int rows = ExecuteNonQuery(command, false);

            return rows > 0;
        }
        /// <summary>
        /// Stores the value of a Setting.
        /// </summary>
        /// <param name="name">The name of the Setting.</param>
        /// <param name="value">The value of the Setting. Value cannot contain CR and LF characters, which will be removed.</param>
        /// <returns>True if the Setting is stored, false otherwise.</returns>
        /// <remarks>This method stores the Value immediately.</remarks>
        public bool SetSetting(string name, string value)
        {
            if(name == null) throw new ArgumentNullException("name");
            if(name.Length == 0) throw new ArgumentException("Name cannot be empty", "name");

            // 1. Delete old value, if any
            // 2. Store new value

            // Nulls are converted to empty strings
            if(value == null) value = "";

            ICommandBuilder builder = GetCommandBuilder();
            DbConnection connection = builder.GetConnection(connString);
            DbTransaction transaction = BeginTransaction(connection);

            QueryBuilder queryBuilder = new QueryBuilder(builder);

            string query = queryBuilder.DeleteFrom("Setting");
            query = queryBuilder.Where(query, "Name", WhereOperator.Equals, "Name");

            List<Parameter> parameters = new List<Parameter>(1);
            parameters.Add(new Parameter(ParameterType.String, "Name", name));

            DbCommand command = builder.GetCommand(transaction, query, parameters);

            int rows = ExecuteNonQuery(command, false);

            if(rows == -1) {
                RollbackTransaction(transaction);
                return false; // Deletion command failed (0-1 are OK)
            }

            query = queryBuilder.InsertInto("Setting",
                new string[] { "Name", "Value" }, new string[] { "Name", "Value" });
            parameters = new List<Parameter>(2);
            parameters.Add(new Parameter(ParameterType.String, "Name", name));
            parameters.Add(new Parameter(ParameterType.String, "Value", value));

            command = builder.GetCommand(transaction, query, parameters);

            rows = ExecuteNonQuery(command, false);

            if(rows == 1) CommitTransaction(transaction);
            else RollbackTransaction(transaction);

            return rows == 1;
        }
        /// <summary>
        /// Removes a Navigation Path.
        /// </summary>
        /// <param name="connection">A database connection.</param>
        /// <param name="path">The navigation path to remove.</param>
        /// <returns><c>true</c> if the path is removed, <c>false</c> otherwise.</returns>
        private bool RemoveNavigationPath(DbConnection connection, NavigationPath path)
        {
            string nspace, name;
            NameTools.ExpandFullName(path.FullName, out nspace, out name);
            if(nspace == null) nspace = "";

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

            string query = queryBuilder.DeleteFrom("NavigationPath");
            query = queryBuilder.Where(query, "Name", WhereOperator.Equals, "Name");
            query = queryBuilder.AndWhere(query, "Namespace", WhereOperator.Equals, "Namespace");

            List<Parameter> parameters = new List<Parameter>(2);
            parameters.Add(new Parameter(ParameterType.String, "Name", name));
            parameters.Add(new Parameter(ParameterType.String, "Namespace", nspace));

            DbCommand command = builder.GetCommand(connection, query, parameters);

            int rows = ExecuteNonQuery(command, false);

            return rows > 0;
        }
        /// <summary>
        /// Stores the outgoing links of a page, overwriting existing data.
        /// </summary>
        /// <param name="page">The full name of the page.</param>
        /// <param name="outgoingLinks">The full names of the pages that <b>page</b> links to.</param>
        /// <returns><c>true</c> if the outgoing links are stored, <c>false</c> otherwise.</returns>
        /// <exception cref="ArgumentNullException">If <b>page</b> or <b>outgoingLinks</b> are <c>null</c>.</exception>
        /// <exception cref="ArgumentException">If <b>page</b> or <b>outgoingLinks</b> are empty.</exception>
        public bool StoreOutgoingLinks(string page, string[] outgoingLinks)
        {
            if(page == null) throw new ArgumentNullException("page");
            if(page.Length == 0) throw new ArgumentException("Page cannot be empty", "page");
            if(outgoingLinks == null) throw new ArgumentNullException("outgoingLinks");

            foreach(string link in outgoingLinks) {
                if(link == null) throw new ArgumentNullException("outgoingLinks");
                if(link.Length == 0) throw new ArgumentException("Link cannot be empty", "outgoingLinks");
            }

            // 1. Delete old values, if any
            // 2. Store new values

            ICommandBuilder builder = GetCommandBuilder();
            DbConnection connection = builder.GetConnection(connString);
            DbTransaction transaction = BeginTransaction(connection);

            QueryBuilder queryBuilder = new QueryBuilder(builder);

            string query = queryBuilder.DeleteFrom("OutgoingLink");
            query = queryBuilder.Where(query, "Source", WhereOperator.Equals, "Source");

            List<Parameter> parameters = new List<Parameter>(1);
            parameters.Add(new Parameter(ParameterType.String, "Source", page));

            DbCommand command = builder.GetCommand(transaction, query, parameters);

            if(ExecuteNonQuery(command, false) < 0) {
                RollbackTransaction(transaction);
                return false;
            }

            foreach(string link in outgoingLinks) {
                query = queryBuilder.InsertInto("OutgoingLink", new string[] { "Source", "Destination" }, new string[] { "Source", "Destination" });

                parameters = new List<Parameter>(2);
                parameters.Add(new Parameter(ParameterType.String, "Source", page));
                parameters.Add(new Parameter(ParameterType.String, "Destination", link));

                command = builder.GetCommand(transaction, query, parameters);

                int rows = ExecuteNonQuery(command, false);

                if(rows != 1) {
                    RollbackTransaction(transaction);
                    return false;
                }
            }

            CommitTransaction(transaction);
            return true;
        }
        /// <summary>
        /// Deletes the Backups of a Page, up to a specified revision.
        /// </summary>
        /// <param name="page">The Page to delete the backups of.</param>
        /// <param name="revision">The newest revision to delete (newer revision are kept) o -1 to delete all the Backups.</param>
        /// <returns><c>true</c> if the deletion succeeded, <c>false</c> otherwise.</returns>
        /// <exception cref="ArgumentNullException">If <paramref name="page"/> is <c>null</c>.</exception>
        /// <exception cref="ArgumentOutOfRangeException">If <paramref name="revision"/> is less than -1.</exception>
        public bool DeleteBackups(PageInfo page, int revision)
        {
            if(page == null) throw new ArgumentNullException("page");
            if(revision < -1) throw new ArgumentOutOfRangeException("revision", "Invalid Revision");

            // 1. Retrieve target content (revision-1 = first kept revision)
            // 2. Replace the current content (delete, store)
            // 3. Delete all older revisions up to the specified on (included) "N-m...N"
            // 4. Re-number remaining revisions starting from FirstRevision (zero) to revision-1 (don't re-number revs -1, -100)

            ICommandBuilder builder = GetCommandBuilder();
            DbConnection connection = builder.GetConnection(connString);
            DbTransaction transaction = BeginTransaction(connection);

            if(GetPage(transaction, page.FullName) == null) {
                RollbackTransaction(transaction);
                return false;
            }

            int[] baks = GetBackups(transaction, page);
            if(baks.Length > 0 && revision > baks[baks.Length - 1]) {
                RollbackTransaction(transaction);
                return true;
            }

            string nspace, name;
            NameTools.ExpandFullName(page.FullName, out nspace, out name);
            if(nspace == null) nspace = "";

            QueryBuilder queryBuilder = new QueryBuilder(builder);

            string query = queryBuilder.DeleteFrom("PageContent");
            query = queryBuilder.Where(query, "Page", WhereOperator.Equals, "Page");
            query = queryBuilder.AndWhere(query, "Namespace", WhereOperator.Equals, "Namespace");
            if(revision != -1) query = queryBuilder.AndWhere(query, "Revision", WhereOperator.LessThanOrEqualTo, "Revision");
            query = queryBuilder.AndWhere(query, "Revision", WhereOperator.GreaterThanOrEqualTo, "FirstRevision");

            List<Parameter> parameters = new List<Parameter>(4);
            parameters.Add(new Parameter(ParameterType.String, "Page", name));
            parameters.Add(new Parameter(ParameterType.String, "Namespace", nspace));
            if(revision != -1) parameters.Add(new Parameter(ParameterType.Int16, "Revision", revision));
            parameters.Add(new Parameter(ParameterType.Int16, "FirstRevision", FirstRevision));

            DbCommand command = builder.GetCommand(transaction, query, parameters);

            int rows = ExecuteNonQuery(command, false);

            if(rows == -1) {
                RollbackTransaction(transaction);
                return false;
            }

            if(revision != -1) {
                int revisionDelta = revision + 1;

                query = queryBuilder.UpdateIncrement("PageContent", "Revision", -revisionDelta);
                query = queryBuilder.Where(query, "Page", WhereOperator.Equals, "Page");
                query = queryBuilder.AndWhere(query, "Namespace", WhereOperator.Equals, "Namespace");
                query = queryBuilder.AndWhere(query, "Revision", WhereOperator.GreaterThanOrEqualTo, "FirstRevision");

                parameters = new List<Parameter>(3);
                parameters.Add(new Parameter(ParameterType.String, "Page", name));
                parameters.Add(new Parameter(ParameterType.String, "Namespace", nspace));
                parameters.Add(new Parameter(ParameterType.Int16, "FirstRevision", FirstRevision));

                command = builder.GetCommand(transaction, query, parameters);

                rows = ExecuteNonQuery(command, false);

                if(rows > 0) CommitTransaction(transaction);
                else RollbackTransaction(transaction);

                return rows >= 0;
            }
            else {
                CommitTransaction(transaction);
                return true;
            }
        }
        /// <summary>
        /// Merges two Categories.
        /// </summary>
        /// <param name="source">The source Category.</param>
        /// <param name="destination">The destination Category.</param>
        /// <returns>The correct <see cref="T:CategoryInfo" /> object.</returns>
        /// <remarks>The destination Category remains, while the source Category is deleted, and all its Pages re-bound 
        /// in the destination Category.</remarks>
        /// <exception cref="ArgumentNullException">If <paramref name="source"/> or <paramref name="destination"/> are <c>null</c>.</exception>
        public CategoryInfo MergeCategories(CategoryInfo source, CategoryInfo destination)
        {
            if(source == null) throw new ArgumentNullException("source");
            if(destination == null) throw new ArgumentNullException("destination");

            // 1. Check for same namespace
            // 2. Load all pages in source
            // 3. Load all pages in destination
            // 4. Merge lists in memory
            // 5. Delete all destination bindings
            // 6. Delete source cat
            // 7. Insert new bindings stored in memory

            string sourceNs = NameTools.GetNamespace(source.FullName);
            string destinationNs = NameTools.GetNamespace(destination.FullName);

            // If one is null and the other not null, fail
            if(sourceNs == null && destinationNs != null || sourceNs != null && destinationNs == null) return null;
            else {
                // Both non-null or both null
                if(sourceNs != null) {
                    // Both non-null, check names
                    NamespaceInfo tempSource = new NamespaceInfo(sourceNs, this, null);
                    NamespaceInfo tempDest = new NamespaceInfo(destinationNs, this, null);
                    // Different names, fail
                    if(new NamespaceComparer().Compare(tempSource, tempDest) != 0) return null;
                }
                // else both null, OK
            }

            string nspace = sourceNs != null ? sourceNs : "";

            ICommandBuilder builder = GetCommandBuilder();
            DbConnection connection = builder.GetConnection(connString);
            DbTransaction transaction = BeginTransaction(connection);

            CategoryInfo actualSource = GetCategory(transaction, source.FullName);
            CategoryInfo actualDestination = GetCategory(transaction, destination.FullName);

            if(actualSource == null) {
                RollbackTransaction(transaction);
                return null;
            }
            if(actualDestination == null) {
                RollbackTransaction(transaction);
                return null;
            }

            string destinationName = NameTools.GetLocalName(actualDestination.FullName);

            string[] mergedPages = MergeArrays(actualSource.Pages, actualDestination.Pages);

            QueryBuilder queryBuilder = new QueryBuilder(builder);

            string query = queryBuilder.DeleteFrom("CategoryBinding");
            query = queryBuilder.Where(query, "Namespace", WhereOperator.Equals, "Namespace");
            query = queryBuilder.AndWhere(query, "Category", WhereOperator.Equals, "Category");

            List<Parameter> parameters = new List<Parameter>(2);
            parameters.Add(new Parameter(ParameterType.String, "Namespace", nspace));
            parameters.Add(new Parameter(ParameterType.String, "Category", destinationName));

            DbCommand command = builder.GetCommand(transaction, query, parameters);

            int rows = ExecuteNonQuery(command, false);

            if(rows == -1) {
                RollbackTransaction(transaction);
                return null;
            }

            if(!RemoveCategory(transaction, source)) {
                RollbackTransaction(transaction);
                return null;
            }

            string finalQuery = "";
            parameters = new List<Parameter>(MaxStatementsInBatch * 3);
            rows = 0;
            int count = 1;
            string countString;

            foreach(string page in mergedPages) {
                // This batch is executed in small chunks (MaxStatementsInBatch) to avoid exceeding DB's max batch length/size

                countString = count.ToString();

                query = queryBuilder.InsertInto("CategoryBinding", new string[] { "Namespace", "Category", "Page" },
                    new string[] { "Namespace" + countString, "Category" + countString, "Page" + countString });
                finalQuery = queryBuilder.AppendForBatch(finalQuery, query);

                parameters.Add(new Parameter(ParameterType.String, "Namespace" + countString, nspace));
                parameters.Add(new Parameter(ParameterType.String, "Category" + countString, destinationName));
                parameters.Add(new Parameter(ParameterType.String, "Page" + countString, NameTools.GetLocalName(page)));

                count++;

                if(count == MaxStatementsInBatch) {
                    // Batch is complete -> execute
                    command = builder.GetCommand(transaction, finalQuery, parameters);
                    rows += ExecuteNonQuery(command, false);

                    count = 1;
                    finalQuery = "";
                    parameters.Clear();
                }
            }

            if(finalQuery.Length > 0) {
                // Execute remaining queries, if any
                command = builder.GetCommand(transaction, finalQuery, parameters);
                rows += ExecuteNonQuery(command, false);
            }

            if(rows == mergedPages.Length) {
                CommitTransaction(transaction);
                CategoryInfo result = new CategoryInfo(actualDestination.FullName, this);
                result.Pages = mergedPages;
                return result;
            }
            else {
                RollbackTransaction(transaction);
                return null;
            }
        }
        /// <summary>
        /// Deletes a directory and all its contents.
        /// </summary>
        /// <param name="transaction">The current transaction to use.</param>
        /// <param name="fullPath">The full path of the directory.</param>
        /// <returns><c>true</c> if the directory is deleted, <c>false</c> otherwise.</returns>
        private bool DeleteDirectory(DbTransaction transaction, string fullPath)
        {
            string[] dirs = ListDirectories(transaction, fullPath);
            foreach(string dir in dirs) {
                if(!DeleteDirectory(transaction, dir)) {
                    return false;
                }
            }

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

            string query = queryBuilder.DeleteFrom("Directory");
            query = queryBuilder.Where(query, "FullPath", WhereOperator.Equals, "FullPath");

            List<Parameter> parameters = new List<Parameter>(2);
            parameters.Add(new Parameter(ParameterType.String, "FullPath", fullPath));

            DbCommand command = builder.GetCommand(transaction, query, parameters);

            int rows = ExecuteNonQuery(command, false);

            return rows > 0;
        }
        /// <summary>
        /// Removes a namespace.
        /// </summary>
        /// <param name="nspace">The namespace to remove.</param>
        /// <returns><c>true</c> if the namespace is removed, <c>false</c> otherwise.</returns>
        /// <exception cref="ArgumentNullException">If <paramref name="nspace"/> is <c>null</c>.</exception>
        public bool RemoveNamespace(NamespaceInfo nspace)
        {
            if(nspace == null) throw new ArgumentNullException("nspace");

            ICommandBuilder builder = GetCommandBuilder();
            DbConnection connection = builder.GetConnection(connString);
            DbTransaction transaction = BeginTransaction(connection);

            foreach(PageInfo page in GetPages(transaction, nspace)) {
                PageContent content = GetContent(transaction, page, CurrentRevision);
                UnindexPage(content, transaction);
                foreach(Message msg in GetMessages(transaction, page)) {
                    UnindexMessageTree(page, msg, transaction);
                }
            }

            QueryBuilder queryBuilder = new QueryBuilder(builder);

            string query = queryBuilder.DeleteFrom("Namespace");
            query = queryBuilder.Where(query, "Name", WhereOperator.Equals, "Name");

            List<Parameter> parameters = new List<Parameter>(1);
            parameters.Add(new Parameter(ParameterType.String, "Name", nspace.Name));

            DbCommand command = builder.GetCommand(transaction, query, parameters);

            int rows = ExecuteNonQuery(command, false);
            if(rows > 0) CommitTransaction(transaction);
            else RollbackTransaction(transaction);

            return rows > 0;
        }
        /// <summary>
        /// Deletes a Page Attachment.
        /// </summary>
        /// <param name="pageInfo">The Page Info that owns the Attachment.</param>
        /// <param name="name">The name of the Attachment, for example "myfile.jpg".</param>
        /// <returns><c>true</c> if the Attachment is deleted, <c>false</c> otherwise.</returns>
        /// <exception cref="ArgumentNullException">If <paramref name="pageInfo"/> or <paramref name="name"/> are <c>null</c>.</exception>
        /// <exception cref="ArgumentException">If <paramref name="name"/> is empty or if the page or attachment do not exist.</exception>
        public bool DeletePageAttachment(PageInfo pageInfo, string name)
        {
            if(pageInfo == null) throw new ArgumentNullException("pageInfo");
            if(name == null) throw new ArgumentNullException("name");
            if(name.Length == 0) throw new ArgumentException("Name cannot be empty");

            ICommandBuilder builder = GetCommandBuilder();
            DbConnection connection = builder.GetConnection(connString);
            DbTransaction transaction = BeginTransaction(connection);

            if(!AttachmentExists(transaction, pageInfo, name)) {
                RollbackTransaction(transaction);
                throw new ArgumentException("Attachment does not exist", "name");
            }

            QueryBuilder queryBuilder = new QueryBuilder(builder);

            string query = queryBuilder.DeleteFrom("Attachment");
            query = queryBuilder.Where(query, "Name", WhereOperator.Equals, "Name");
            query = queryBuilder.AndWhere(query, "Page", WhereOperator.Equals, "Page");

            List<Parameter> parameters = new List<Parameter>(2);
            parameters.Add(new Parameter(ParameterType.String, "Name", name));
            parameters.Add(new Parameter(ParameterType.String, "Page", pageInfo.FullName));

            DbCommand command = builder.GetCommand(transaction, query, parameters);

            int rows = ExecuteNonQuery(command, false);
            if(rows == 1) CommitTransaction(transaction);
            else RollbackTransaction(transaction);

            return rows == 1;
        }
        /// <summary>
        /// Removes a Page.
        /// </summary>
        /// <param name="page">The Page to remove.</param>
        /// <returns>True if the Page is removed successfully.</returns>
        /// <exception cref="ArgumentNullException">If <paramref name="page"/> is <c>null</c>.</exception>
        public bool RemovePage(PageInfo page)
        {
            if(page == null) throw new ArgumentNullException("page");

            ICommandBuilder builder = GetCommandBuilder();
            DbConnection connection = builder.GetConnection(connString);
            DbTransaction transaction = BeginTransaction(connection);

            if(IsDefaultPage(transaction, page)) {
                RollbackTransaction(transaction);
                return false;
            }

            PageContent currentContent = GetContent(transaction, page, CurrentRevision);
            if(currentContent != null) {
                UnindexPage(currentContent, transaction);
                foreach(Message msg in GetMessages(transaction, page)) {
                    UnindexMessageTree(page, msg, transaction);
                }
            }

            RebindPage(transaction, page, new string[0]);

            string nspace, name;
            NameTools.ExpandFullName(page.FullName, out nspace, out name);
            if(nspace == null) nspace = "";

            QueryBuilder queryBuilder = new QueryBuilder(builder);

            string query = queryBuilder.DeleteFrom("Page");
            query = queryBuilder.Where(query, "Name", WhereOperator.Equals, "Name");
            query = queryBuilder.AndWhere(query, "Namespace", WhereOperator.Equals, "Namespace");

            List<Parameter> parameters = new List<Parameter>(2);
            parameters.Add(new Parameter(ParameterType.String, "Name", name));
            parameters.Add(new Parameter(ParameterType.String, "Namespace", nspace));

            DbCommand command = builder.GetCommand(transaction, query, parameters);

            int rows = ExecuteNonQuery(command, false);

            if(rows > 0) CommitTransaction(transaction);
            else RollbackTransaction(transaction);

            return rows > 0;
        }
        /// <summary>
        /// Clears the index.
        /// </summary>
        /// <param name="state">A state object passed from the index.</param>
        private void ClearIndex(object state)
        {
            // state can be null, depending on when the method is called

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

            string query = queryBuilder.DeleteFrom("IndexWordMapping");
            query = queryBuilder.AppendForBatch(query, queryBuilder.DeleteFrom("IndexWord"));
            query = queryBuilder.AppendForBatch(query, queryBuilder.DeleteFrom("IndexDocument"));

            DbCommand command = null;
            if(state == null) command = builder.GetCommand(connString, query, new List<Parameter>());
            else command = builder.GetCommand((DbTransaction)state, query, new List<Parameter>());

            ExecuteNonQuery(command, state == null);
        }
        /// <summary>
        /// Removes a user data element.
        /// </summary>
        /// <param name="transaction">A database transaction.</param>
        /// <param name="username">The username.</param>
        /// <param name="key">The key.</param>
        /// <returns><c>true</c> if the data element is removed, <c>false</c> otherwise.</returns>
        private bool RemoveUserData(DbTransaction transaction, string username, string key)
        {
            ICommandBuilder builder = GetCommandBuilder();
            QueryBuilder queryBuilder = new QueryBuilder(builder);

            string query = queryBuilder.DeleteFrom("UserData");
            query = queryBuilder.Where(query, "User", WhereOperator.Equals, "Username");
            query = queryBuilder.AndWhere(query, "Key", WhereOperator.Equals, "Key");

            List<Parameter> parameters = new List<Parameter>(2);
            parameters.Add(new Parameter(ParameterType.String, "Username", username));
            parameters.Add(new Parameter(ParameterType.String, "Key", key));

            DbCommand command = builder.GetCommand(transaction, query, parameters);

            int rows = ExecuteNonQuery(command, false);

            return rows != -1; // Success also if no elements are removed
        }