Applied SQL…

In this article we will see how we can remove partitions from a table in a database in SQL server. In my previous post i had demonstrated how we can partition a table via T-SQL. Lets now remove the partitions and merge the data in a single partition. I will start from where we left off in my previous post of partitioning a table.

1) Run the below code to create a database named PartitionDB that would include a table that has been partitioned.

USE master
GO
CREATE DATABASE PartitionDB
ON PRIMARY (NAME = N'PartitionDB'
,FILENAME = N'D:\MSSQL\Data\PartitionDB.mdf'
,SIZE = 50MB, FILEGROWTH = 150MB)
LOG ON (
NAME = N'PartitionDB_log'
,FILENAME = N'D:\MSSQL\Logs\PartitionDB_log.ldf'
,SIZE = 10MB, FILEGROWTH = 100MB);
GO

ALTER DATABASE PartitionDB ADD FILEGROUP PartitionFG1;
GO
ALTER DATABASE PartitionDB ADD FILEGROUP PartitionFG2;
GO
ALTER DATABASE PartitionDB ADD FILEGROUP PartitionFG3;
GO
ALTER DATABASE PartitionDB ADD FILEGROUP PartitionFG4;
GO

ALTER DATABASE PartitionDB
    ADD FILE
    (
        NAME = PartitionFile1,
        FILENAME = 'D:\MSSQL\Data\PartitionFile1.ndf',
        SIZE = 20MB, MAXSIZE = 50MB, FILEGROWTH = 5MB
    )
    TO FILEGROUP PartitionFG1;
GO

ALTER DATABASE PartitionDB
    ADD FILE
    (
        NAME = PartitionFile2,
        FILENAME = 'D:\MSSQL\Data\PartitionFile2.ndf',
        SIZE = 20MB, MAXSIZE = 50MB, FILEGROWTH = 5MB
    )
    TO FILEGROUP PartitionFG2;
GO

ALTER DATABASE PartitionDB
    ADD FILE
    (
        NAME = PartitionFile3,
        FILENAME = 'D:\MSSQL\Data\PartitionFile3.ndf',
        SIZE = 20MB, MAXSIZE = 50MB, FILEGROWTH = 5MB
    )
    TO FILEGROUP PartitionFG3;
GO

ALTER DATABASE PartitionDB
    ADD FILE
    (
        NAME = PartitionFile4,
        FILENAME = 'D:\MSSQL\Data\PartitionFile4.ndf',
        SIZE = 20MB, MAXSIZE = 50MB, FILEGROWTH = 5MB
    )
    TO FILEGROUP PartitionFG4;
GO

CREATE PARTITION FUNCTION PartFunc1 (int)
    AS RANGE LEFT FOR VALUES (10, 20, 30);
GO

CREATE PARTITION SCHEME PartScheme1
    AS PARTITION PartFunc1
    TO (PartitionFG1, PartitionFG2,PartitionFG3,PartitionFG4);
GO

USE [PartitionDB]
GO
CREATE TABLE PartitionTable
    (
    MyID int NOT NULL,
    MyDate datetime NULL,
    Name varchar(50) NULL
    )  ON PartScheme1(MyID)
GO
USE PartitionDB
go
CREATE UNIQUE CLUSTERED INDEX IX_PartitionTable
ON PartitionTable(MyID)
ON PartScheme1 (MyID);
GO

USE PartitionDB
go
INSERT INTO PartitionTable (MyID, MyDate,name)
VALUES (1,GETDATE(),'Rooney');
INSERT INTO PartitionTable (MyID, MyDate,name)
VALUES (11,GETDATE(),'Van persie');
INSERT INTO PartitionTable (MyID, MyDate,name)
VALUES (22,GETDATE(),'De Gea');
INSERT INTO PartitionTable (MyID, MyDate,name)
VALUES (34,GETDATE(),'Moyes');
GO

Run the below code to see the details of the partitioned table

USE PartitionDB
GO
SELECT
OBJECT_NAME(idx.object_id) AS TableName ,
psh.name AS PartitionSchemeName ,
fnc.name AS PartitionFunctionName,
part.partition_number AS PartitionNumber ,
fg.name AS [Filegroup],
rows AS 'No of Records' ,
CASE boundary_value_on_right WHEN 1 THEN 'less than'
ELSE 'less than or equal to' END AS 'Condition',
value AS 'Range' ,
part.partition_id AS [Partition Id] FROM sys.partitions part
JOIN sys.indexes idx
ON part.object_id = idx.object_id
AND part.index_id = idx.index_id JOIN sys.partition_schemes psh
ON psh.data_space_id = idx.data_space_id
JOIN
sys.partition_functions fnc
ON fnc.function_id = psh.function_id LEFT
JOIN sys.partition_range_values prv
ON fnc.function_id = prv.function_id
AND part.partition_number = prv.boundary_id
JOIN sys.destination_data_spaces dds
ON dds.partition_scheme_id = psh.data_space_id
AND dds.destination_id = part.partition_number
JOIN sys.filegroups fg
ON dds.data_space_id = fg.data_space_id
JOIN (SELECT container_id, sum(total_pages) as total_pages
FROM
sys.allocation_units GROUP BY container_id) AS au
ON au.container_id = part.partition_id JOIN sys.tables t ON
part.object_id = t.object_id WHERE idx.index_id < 2
ORDER BY TableName,part.partition_number;
GO

Now let us understand how we can remove the partitions from this table.
The easiest way to do this is to drop the Clustered index from this table and recreate it on another filegroup.

Step 1: Drop the clustered index from the table

USE [PartitionDB]
GO
DROP INDEX [IX_PartitionTable] ON
[dbo].[PartitionTable] WITH ( ONLINE = OFF )
GO

Step 2: Re-create the clustered index on another Filegroup. We will use the primary FG as example

USE [PartitionDB]
GO
CREATE UNIQUE CLUSTERED INDEX [IX_PartitionTable] ON
[dbo].[PartitionTable]
(
 [MyID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF,
SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF,
DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON,
ALLOW_PAGE_LOCKS = ON)
ON [PRIMARY]
GO

Step 3: Verify the state of the partitions by running the below code. You will find that there is only one partition with all the 4 rows in it.

USE PartitionDB
go
SELECT * FROM sys.partitions
WHERE OBJECT_NAME(OBJECT_ID)='partitiontable';
GO

You can verify the same via SSMS by performing the following steps:
Step 1: Right click on the table
Step 2: Click on properties
Step 3: Click on Storage
Step 4 : Verify that “Table is partitioned” is false.
I hope this article was helpful in understanding how we can remove Partitioning from table.