About Updating and Migrating

-- 1. Delete group subscriptions

DECLARE @rowCount BIGINT = 1
DECLARE @batchSize BIGINT = 4000
DECLARE @pivotDate DATETIME = GETUTCDATE()
WHILE (@rowCount > 0)
BEGIN
    DECLARE @subscriptionsToDeleteIds TABLE(
        [Id] UNIQUEIDENTIFIER NOT NULL
    )
    INSERT INTO @subscriptionsToDeleteIds
    SELECT TOP(@batchSize) [ns].[Id]
    FROM [dbo].[NotificationSubscriptions] [ns]
    JOIN [dbo].[Users] [u] ON [u].[Id] = [ns].[UserId]
    WHERE [u].[Type] = 3 AND -- Group
        [u].[CreationTime] <= @pivotDate AND
        [u].[IsDeleted] = 0
    DELETE FROM [dbo].[NotificationSubscriptions]
    WHERE [Id] IN (
        SELECT [Id] FROM @subscriptionsToDeleteIds
    )
    OPTION (MAXDOP 1)
    SET @rowCount = @@ROWCOUNT
    WAITFOR DELAY '00:00:00.1'
END

-- 2. Create index on UserNotifications

IF NOT EXISTS(SELECT * FROM sys.indexes WHERE OBJECT_ID = OBJECT_ID(N'[dbo].[UserNotifications]') AND NAME = N'IX_UserId_CreationTime')
   CREATE NONCLUSTERED INDEX [IX_UserId_CreationTime] ON [dbo].[UserNotifications]
   (
       [UserId] ASC,
       [CreationTime] ASC
   ) INCLUDE ([TenantNotificationId]) WITH (ONLINE = ON);-- 1. Delete group subscriptions

DECLARE @rowCount BIGINT = 1
DECLARE @batchSize BIGINT = 4000
DECLARE @pivotDate DATETIME = GETUTCDATE()
WHILE (@rowCount > 0)
BEGIN
    DECLARE @subscriptionsToDeleteIds TABLE(
        [Id] UNIQUEIDENTIFIER NOT NULL
    )
    INSERT INTO @subscriptionsToDeleteIds
    SELECT TOP(@batchSize) [ns].[Id]
    FROM [dbo].[NotificationSubscriptions] [ns]
    JOIN [dbo].[Users] [u] ON [u].[Id] = [ns].[UserId]
    WHERE [u].[Type] = 3 AND -- Group
        [u].[CreationTime] <= @pivotDate AND
        [u].[IsDeleted] = 0
    DELETE FROM [dbo].[NotificationSubscriptions]
    WHERE [Id] IN (
        SELECT [Id] FROM @subscriptionsToDeleteIds
    )
    OPTION (MAXDOP 1)
    SET @rowCount = @@ROWCOUNT
    WAITFOR DELAY '00:00:00.1'
END

-- 2. Create index on UserNotifications

IF NOT EXISTS(SELECT * FROM sys.indexes WHERE OBJECT_ID = OBJECT_ID(N'[dbo].[UserNotifications]') AND NAME = N'IX_UserId_CreationTime')
   CREATE NONCLUSTERED INDEX [IX_UserId_CreationTime] ON [dbo].[UserNotifications]
   (
       [UserId] ASC,
       [CreationTime] ASC
   ) INCLUDE ([TenantNotificationId]) WITH (ONLINE = ON);