public void RunSynchronously()
        {
            if (!store.Configuration.RunDocumentMigrationsOnStartup)
                return;

            var migrator = new DocumentMigrator(store.Configuration);

            foreach (var table in configuration.Tables.Values.OfType<DocumentTable>())
            {
                var baseDesign = configuration.DocumentDesigns.First(x => x.Table.Name == table.Name);

                while (true)
                {
                    QueryStats stats;
                    var rows = store
                        .Query(table, out stats,
                            @where: "AwaitsReprojection = @AwaitsReprojection or Version < @version",
                            @select: "Id, AwaitsReprojection, Version, Discriminator, Etag",
                            take: 100,
                            @orderby: "newid()",
                            parameters: new {AwaitsReprojection = true, version = configuration.ConfiguredVersion})
                        .ToList();

                    if (stats.TotalResults == 0) break;

                    logger.Information("Found {0} document that must be migrated.", stats.TotalResults);

                    foreach (var row in rows)
                    {
                        var discriminator = ((string)row[table.DiscriminatorColumn]).Trim();

                        DocumentDesign concreteDesign;
                        if (!baseDesign.DecendentsAndSelf.TryGetValue(discriminator, out concreteDesign))
                        {
                            throw new InvalidOperationException(
                                string.Format("Discriminator '{0}' was not found in configuration.", discriminator));
                        }

                        var id = (string)row[table.IdColumn];
                        var currentDocumentVersion = (int)row[table.VersionColumn];

                        var shouldUpdate = false;

                        if ((bool)row[table.AwaitsReprojectionColumn])
                        {
                            shouldUpdate = true;
                            logger.Information("Reprojection document {0}/{1}.",
                                concreteDesign.DocumentType.FullName, id, currentDocumentVersion, configuration.ConfiguredVersion);
                        }

                        if (migrator.ApplicableCommands(concreteDesign, currentDocumentVersion).Any())
                        {
                            shouldUpdate = true;
                        }

                        if (shouldUpdate)
                        {
                            try
                            {
                                var rowWithDocument = store.Get(table, id);

                                var document = (byte[]) rowWithDocument[table.DocumentColumn];
                                var etag = (Guid)rowWithDocument[table.EtagColumn];

                                var entity = migrator.DeserializeAndMigrate(concreteDesign, id, document, currentDocumentVersion);
                                var projections = concreteDesign.Projections.ToDictionary(x => x.Key, x => x.Value.Projector(entity));

                                store.Execute(new BackupCommand(
                                    new UpdateCommand(table, id, etag, projections, false),
                                    store.Configuration.BackupWriter, concreteDesign, id, currentDocumentVersion, document));
                            }
                            catch (ConcurrencyException) {}
                            catch (Exception exception)
                            {
                                logger.Error(exception, "Error while migrating document of type {0} with id {1}.", concreteDesign.DocumentType.FullName, id);
                                Thread.Sleep(100);
                            }
                        }
                        else
                        {
                            logger.Information("Document did not change.");

                            var projection = new Dictionary<string, object>
                            {
                                {table.VersionColumn, configuration.ConfiguredVersion}
                            };

                            store.Update(table, id, (Guid)row[table.EtagColumn], projection);
                        }
                    }
                }
            }
        }
        public Task Run(IDocumentStore store)
        {
            var logger = store.Configuration.Logger;
            var configuration = store.Configuration;

            if (!configuration.RunDocumentMigrationsOnStartup)
                return Task.FromResult(0);

            return Task.Factory.StartNew(() =>
            {
                var migrator = new DocumentMigrator(configuration);

                foreach (var table in configuration.Tables.Values.OfType<DocumentTable>())
                {
                    var baseDesign = configuration.TryGetDesignByTablename(table.Name);
                    if (baseDesign == null)
                    {
                        throw new InvalidOperationException($"Design not found for table '{table.Name}'");
                    }

                    while (true)
                    {
                        QueryStats stats;

                        var rows = store
                            .Query(table, out stats,
                                @where: "AwaitsReprojection = @AwaitsReprojection or Version < @version",
                                @select: "Id, AwaitsReprojection, Version, Discriminator, Etag",
                                take: 100,
                                @orderby: "newid()",
                                parameters: new { AwaitsReprojection = true, version = configuration.ConfiguredVersion })
                            .ToList();

                        if (stats.TotalResults == 0) break;

                        logger.Information("Found {0} document that must be migrated.", stats.TotalResults);

                        foreach (var row in rows)
                        {
                            var key = (string)row[table.IdColumn];
                            var currentDocumentVersion = (int)row[table.VersionColumn];
                            var discriminator = ((string)row[table.DiscriminatorColumn]).Trim();
                            var concreteDesign = store.Configuration.GetOrCreateDesignByDiscriminator(baseDesign, discriminator);

                            var shouldUpdate = false;

                            if ((bool)row[table.AwaitsReprojectionColumn])
                            {
                                shouldUpdate = true;
                                logger.Information("Reprojection document {0}/{1}.",
                                    concreteDesign.DocumentType.FullName, key, currentDocumentVersion, configuration.ConfiguredVersion);
                            }

                            if (migrator.ApplicableCommands(concreteDesign, currentDocumentVersion).Any())
                            {
                                shouldUpdate = true;
                            }

                            if (shouldUpdate)
                            {
                                try
                                {
                                    using (var session = new DocumentSession(store))
                                    {
                                        session.Load(concreteDesign.DocumentType, key);
                                        session.SaveChanges(lastWriteWins: false, forceWriteUnchangedDocument: true);
                                    }
                                }
                                catch (ConcurrencyException) { }
                                catch (Exception exception)
                                {
                                    logger.Error(exception, "Error while migrating document of type {0} with id {1}.", concreteDesign.DocumentType.FullName, key);
                                    Thread.Sleep(100);
                                }
                            }
                            else
                            {
                                logger.Information("Document did not change.");

                                var projection = new Dictionary<string, object>
                                {
                                    {table.VersionColumn, configuration.ConfiguredVersion}
                                };

                                store.Update(table, key, (Guid)row[table.EtagColumn], projection);
                            }
                        }
                    }
                }

            }, TaskCreationOptions.LongRunning);
        }
        public Task Run(IDocumentStore store)
        {
            var logger        = store.Configuration.Logger;
            var configuration = store.Configuration;

            if (!configuration.RunDocumentMigrationsOnStartup)
            {
                return(Task.FromResult(0));
            }

            return(Task.Factory.StartNew(() =>
            {
                var migrator = new DocumentMigrator(configuration);

                foreach (var table in configuration.Tables.Values.OfType <DocumentTable>())
                {
                    var baseDesign = configuration.DocumentDesigns.First(x => x.Table.Name == table.Name);

                    while (true)
                    {
                        QueryStats stats;

                        var rows = store
                                   .Query(table, out stats,
                                          @where: "AwaitsReprojection = @AwaitsReprojection or Version < @version",
                                          @select: "Id, AwaitsReprojection, Version, Discriminator, Etag",
                                          take: 100,
                                          @orderby: "newid()",
                                          parameters: new { AwaitsReprojection = true, version = configuration.ConfiguredVersion })
                                   .ToList();

                        if (stats.TotalResults == 0)
                        {
                            break;
                        }

                        logger.Information("Found {0} document that must be migrated.", stats.TotalResults);

                        foreach (var row in rows)
                        {
                            var key = (string)row[table.IdColumn];
                            var currentDocumentVersion = (int)row[table.VersionColumn];
                            var discriminator = ((string)row[table.DiscriminatorColumn]).Trim();
                            var concreteDesign = store.Configuration.GetOrCreateConcreteDesign(baseDesign, discriminator, key);

                            var shouldUpdate = false;

                            if ((bool)row[table.AwaitsReprojectionColumn])
                            {
                                shouldUpdate = true;
                                logger.Information("Reprojection document {0}/{1}.",
                                                   concreteDesign.DocumentType.FullName, key, currentDocumentVersion, configuration.ConfiguredVersion);
                            }

                            if (migrator.ApplicableCommands(concreteDesign, currentDocumentVersion).Any())
                            {
                                shouldUpdate = true;
                            }

                            if (shouldUpdate)
                            {
                                try
                                {
                                    using (var session = new DocumentSession(store))
                                    {
                                        session.Load(concreteDesign, key);
                                        session.SaveChanges(lastWriteWins: false, forceWriteUnchangedDocument: true);
                                    }
                                }
                                catch (ConcurrencyException) { }
                                catch (Exception exception)
                                {
                                    logger.Error(exception, "Error while migrating document of type {0} with id {1}.", concreteDesign.DocumentType.FullName, key);
                                    Thread.Sleep(100);
                                }
                            }
                            else
                            {
                                logger.Information("Document did not change.");

                                var projection = new Dictionary <string, object>
                                {
                                    { table.VersionColumn, configuration.ConfiguredVersion }
                                };

                                store.Update(table, key, (Guid)row[table.EtagColumn], projection);
                            }
                        }
                    }
                }
            }, TaskCreationOptions.LongRunning));
        }