Dropped FileGroup/Files still show up in Sys.Master_Files and MSDB.dbo.backupfile

Question

 Hello all,
I am wondering why is that when a filegroup/file is removed from the DB, it still shows up in sys.master_files and msdb.dbo.backupfile.
To reproduce, just create a database and add a filegroup or file to an existing file and delete that filegroup\file.
Now,Query Sys.master_files and you can still see the deleted Filegroup/file for the database. Of course the State_desc shows as 'Offline' but I am wondering why it is not removed completely.
Also, if you take a backup and query the msdb.dbo.backupfile, it will show up there as well. Again, State_desc = 'Dropped' but why is it not removed completely.
Thank you and have a wonderful day.
Hope it Helps!!

Answer 1

Hi Andrew--Msdb.dbo.backupfile showing online is correct because the backup was taken when file group was active. However, I do not see what you are seeing, ie, when I drop the filegroup/file, i still see it in the sys.master_files. and in msdb.dbo.backupfile.
I tested this is on both sql2008R2 build 10.50.4000 and sql 2012 sp1.
below is the script..
CREATE DATABASE [TestFileGroup] ON PRIMARY
( NAME = N'TestFileGroup', FILENAME = N'F:\Backup\TestFileGroup.mdf' , SIZE = 4072KB , FILEGROWTH = 1024KB ),
FILEGROUP [TestFG]
( NAME = N'TestFile', FILENAME = N'F:\Backup\TestFile.ndf' , SIZE = 4072KB , FILEGROWTH= 1024KB )
LOG ON
( NAME = N'TestFileGroup_log', FILENAME = N'F:\Backup\TestFileGroup_log.ldf' , SIZE = 1024KB , FILEGROWTH = 10%)
GO
USE [TestFileGroup]
GO
IF NOT EXISTS (SELECT name FROM sys.filegroups WHERE is_default=1 AND name = N'PRIMARY')
ALTER DATABASE [TestFileGroup] MODIFY FILEGROUP [PRIMARY] DEFAULT
GO
select state_desc,Name,getdate() from sys.master_files where database_id= db_ID('TestFileGroup')
BACKUP DATABASE testFileGroup TO DISK = N'F:\Backup\TestFG.bak' with init,Format
USE [TestFileGroup]
GO
ALTER DATABASE [TestFileGroup] REMOVE FILE [TestFile]
GO
ALTER DATABASE [TestFileGroup] REMOVE FILEGROUP [TestFG]
GO
select State_desc,Name,getdate() from sys.master_files where database_id= db_ID('TestFileGroup')
BACKUP DATABASE testFileGroup TO DISK = N'F:\Backup\TestFG.bak' with init,Format
select A.Backup_set_id,A.State_desc,logical_name,Database_Name,getdate() from msdb.dbo.backupfile A Inner join msdb.dbo.backupset B on B.backup_set_id=A.backup_set_id
where database_Name = 'TestFileGroup' and A.backup_set_id = (Select max(backup_set_id) from msdb.dbo.backupset where database_Name = 'TestFileGroup' )
The above queried also returned 'DROPPED' filegroup. (I could upload the screen shot but it errors saying i could upload only 2 images)
I tired querying the sys.master_files and took a backup and queried msdb.dbo.backupfile after restarting the instance and I still see the same thing...
Hope it Helps!!