Why does a newly-inserted row show up in two filegroups on a partitioned table in SQL Server?

Question

I partitioned an existing table by year. After inserting a new record for a date in 2020, the new record shows as part of the 2020 partition and in the primary filegroup. I'm having a hard time finding if that's what is supposed to happen, or if I have something configured incorrectly.

This is what the partitions look like after inserting the record. Before inserting the record, this query showed 3 records in the primary filegroup, and 3 records in the 2021 group.

I was expecting a new row in the 2020 partition and for the number of rows in the primary filegroup to remain at 3, but perhaps those are wrong expectations.

Does the primary filegroup always show the total of the partitions, or should rows only show up as being in just the partition in which they belong?

I can show how I set this all up, and I'd be happy to, but this question is more about what the results should look like. I don't want the same row in multiple partitions.

Edit

I just found this link. It shows the results of inserting data where new rows only show up in the correct partition and not also in primary. So it appears I've done something incorrectly.

https://www.sqlshack.com/how-to-automate-table-partitioning-in-sql-server/

Edit 2

The reason primary has all 4 rows may be that its upper boundary is null. Since primary already existed on the table, that was never modified. Perhaps I need to modify it?

Edit 3

Interesting that this link also shows the sum of the partitions within the primary.

https://www.mssqltips.com/sqlservertip/2888/how-to-partition-an-existing-sql-server-table/

Script that SSMS generated for partitioning

USE [Sandbox]
GO
BEGIN TRANSACTION
CREATE PARTITION FUNCTION [PunchPF1](datetimeoffset(7)) AS RANGE LEFT FOR VALUES (N'2020-01-01T00:00:00-05:00', N'2021-01-01T00:00:00-05:00', N'2022-01-01T00:00:00-05:00')
 
CREATE PARTITION SCHEME [PunchPS1] AS PARTITION [PunchPF1] TO ([Pre2020_Punch], [2020_Punch], [2021_Punch], [2022_Punch])
 
ALTER TABLE [time].[Punch] DROP CONSTRAINT [PK_Punch] WITH ( ONLINE = OFF )
 
ALTER TABLE [time].[Punch] ADD  CONSTRAINT [PK_Punch] PRIMARY KEY NONCLUSTERED 
(
    [Id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
 
CREATE CLUSTERED INDEX [ClusteredIndex_on_PunchPS1_637515095430656187] ON [time].[Punch]
(
    [PunchTime]
)WITH (SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF) ON [PunchPS1]([PunchTime])
 
DROP INDEX [ClusteredIndex_on_PunchPS1_637515095430656187] ON [time].[Punch]
 
COMMIT TRANSACTION

Edit 4

Here is the same query, but with IndexName and IndexID included.

Edit 5

Things look better now after doing this:

USE [Sandbox]

--------------------------------------------------------------------------------------------------------------------
-- Drop table, scheme, and function
IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLES where TABLE_NAME = 'Punch' AND TABLE_SCHEMA = 'time')
    DROP TABLE time.Punch;

IF EXISTS (SELECT 1 FROM sys.partition_schemes WHERE name = 'PunchPS1')
    DROP PARTITION SCHEME PunchPS1

IF EXISTS (SELECT 1 FROM sys.partition_functions WHERE name = 'PunchPF1')
    DROP partition function PunchPF1

--------------------------------------------------------------------------------------------------------------------
-- Files and Filegroups
-- Add files and filegroups manually in SSMS because each SQL Server could have different file locations?
-- How to add a file and filegroup using SQL:
-- https://docs.microsoft.com/en-us/sql/t-sql/statements/alter-database-transact-sql-file-and-filegroup-options?view=sql-server-ver15
-- To see an example of creating filegroups in SQL, script the Sandbox DB AS CREATE...

--------------------------------------------------------------------------------------------------------------------
-- Partition Function
CREATE PARTITION FUNCTION [PunchPF1](datetimeoffset(7))
AS RANGE RIGHT FOR VALUES (N'2020-01-01T00:00:00-05:00', N'2021-01-01T00:00:00-05:00', N'2022-01-01T00:00:00-05:00')

-------------------------------------------------------------------------------------------------------------------- 
-- Partition Scheme
CREATE PARTITION SCHEME [PunchPS1]
AS PARTITION [PunchPF1] TO ([Pre2020_Punch], [2020_Punch], [2021_Punch], [2022_Punch])

--------------------------------------------------------------------------------------------------------------------
-- Table
CREATE TABLE [time].[Punch](
    [Id] [bigint] IDENTITY(1,1) NOT NULL,
    [EmployeeId] [bigint] NOT NULL,
    [PunchTime] [datetimeoffset](7) NOT NULL
) ON [PunchPS1] (PunchTime)

--------------------------------------------------------------------------------------------------------------------
-- Add some data
INSERT INTO [time].[Punch] ([EmployeeId],[PunchTime]) VALUES (10,'2020-12-18 16:40:20')
INSERT INTO [time].[Punch] ([EmployeeId],[PunchTime]) VALUES (10,'2020-12-20 16:40:20')
INSERT INTO [time].[Punch] ([EmployeeId],[PunchTime]) VALUES (10,'2020-12-22 16:40:20')
INSERT INTO [time].[Punch] ([EmployeeId],[PunchTime]) VALUES (10,'2021-3-18 16:40:20')

As seen here, the boundaries look good, I'm using RANGE RIGHT, and the rows seem to show in the correct partition.

The only question I have now is if it's bad to have no clustered index?

Answer 1

You have an index and a heap (the unindexed table) as shown by indexid (3 & 0 respectively) in edit4 so of course the row shows up twice. The index called PK_Punch does not seem to be partition aligned (as it is NULL in PartitionScheme) - which may or may not be a problem.