Monday, April 8, 2013

Duplicate table structure and indexes for switch partition

When you want to perform a SWITCH PARTITION statement, you need to duplicate the table structure you are switching. See this article for more details about partitioning.
As far as I know, there is no such a native capability in SQL Server. You may try
SELECT * INTO <your_switch_table> FROM <your_original_table>

But this will only copy the list of columns, not the indexes that are needed for partition switch. What is more, the table will be created in default filegroup, where you would prefer the partitioned filegroup.

So I wrote a stored procedure that creates a copy of the table structure, indexes (clustered an non-clustered), and allows some options for the storage filegroup.


/*
This stored procedure generates a SQL script that creates a copy of SQL
table and indexes. Some options allow to fine-tune the generated script,
like include indexes or not, change the filegroup of table, etc.
*/
CREATE PROCEDURE SCRIPT_CREATE_TABLE
 @OriginalSchemaName SYSNAME,
 @OriginalTableName SYSNAME,
 @TargetSchemaName SYSNAME,
 @TargetTableName SYSNAME,
 @OutputQuery VARCHAR(MAX) OUTPUT,
 @FilegroupToUse SYSNAME = NULL,
 @ScriptIndexes BIT = 1
AS
BEGIN

/*
 References
 http://stackoverflow.com/questions/21547/in-sql-server-how-do-i-generate-a-create-table-statement-for-a-given-table
 http://www.sqlteam.com/forums/topic.asp?TOPIC_ID=125819
 http://ranjithk.com/2010/01/31/how-to-determine-the-file-group-of-a-table-or-a-index/
 http://stackoverflow.com/questions/1121522/generate-create-scripts-for-a-list-of-indexes
*/

BEGIN TRY


/* ******************************** */
/* FIND THE OBJECT_ID CORRESPONDING */
/* TO THE ORIGINAL TABLE            */
/* ******************************** */
SET @OutputQuery = ''
DECLARE @Msg VARCHAR(MAX)
DECLARE @TableId INT = NULL

SELECT @TableId = t.object_id
FROM sys.tables t
INNER JOIN sys.schemas s ON s.schema_id = t.schema_id
INNER JOIN sys.columns c ON c.object_id = t.object_id
WHERE s.name = @OriginalSchemaName
AND t.name = @OriginalTableName

IF @TableId IS NULL
 BEGIN
 SET @Msg = 'Cannot find table [' + @OriginalSchemaName + '].[' + @OriginalTableName + ']'
 RAISERROR(@Msg, 16, 1)
 END




/* ************************************* */
/* FIND THE FILEGROUP / PARTITION SCHEME */
/* TO BE USED IN TARGET TABLE            */
/* ************************************* */

DECLARE @TargetFilegroup VARCHAR(MAX) = NULL
IF @FilegroupToUse IS NULL OR @FilegroupToUse = ''
 /* No filegroup specified, find the original one */
 BEGIN
 
 DECLARE @OriginalFilegroup VARCHAR(MAX) = NULL
 
 /* First, try to find a partition scheme used by the table */
 SELECT @OriginalFilegroup = '[' + ps.name + ']([' + c.name + '])'
 FROM sys.tables t
 INNER JOIN sys.schemas s ON s.schema_id = t.schema_id
 INNER JOIN sys.indexes i ON i.object_id = t.object_id
 INNER JOIN sys.partition_schemes ps ON ps.data_space_id = i.data_space_id
 INNER JOIN sys.partition_functions pf ON pf.function_id = ps.function_id
 INNER JOIN sys.index_columns ic ON ic.partition_ordinal > 0 AND ic.index_id = i.index_id AND ic.object_id = t.object_id
 INNER JOIN sys.columns c ON c.object_id = ic.object_id AND c.column_id = ic.column_id
 WHERE i.[type] IN (0, 1) /* Index of type HEAP or CLUSTERED */
 AND s.name = @OriginalSchemaName
 AND t.name = @OriginalTableName
 
 /* If no partition shceme found, try to find a regular filegroup */
 IF @OriginalFilegroup IS NULL
  BEGIN
  SELECT @OriginalFilegroup = '[' + d.name + ']'
  FROM sys.filegroups d
  INNER JOIN sys.indexes i ON i.data_space_id = d.data_space_id
  INNER JOIN sys.tables t ON t.object_id = i.object_id
  WHERE i.index_id < 2
  AND t.name = @OriginalTableName
  AND t.schema_id = schema_id(@OriginalSchemaName)
  END

 /* No regular filegroup neither partition shceme found, there is a problem */
 IF @OriginalFilegroup IS NULL
  BEGIN
  SET @Msg = 'Could not find filegroup neither partition scheme for table [' + @OriginalSchemaName + '].[' + @OriginalTableName + ']'
  RAISERROR(@Msg, 16, 1)
  END
  
 SET @TargetFilegroup = @OriginalFilegroup
 
 END
ELSE
 /* A filegroup has been specified, just use this one */
 BEGIN
 SET @TargetFilegroup = @FilegroupToUse
 END




/* ******************************* */
/* GENERATE CREATE TABLE STATEMENT */
/* ******************************* */

DECLARE @SqlQuery_CreateTable VARCHAR(MAX)
SELECT  @SqlQuery_CreateTable = 'CREATE TABLE [' + @TargetSchemaName + '].[' + @TargetTableName + ']
(
' + o.list +
') ON ' + @TargetFilegroup + '
WITH ( DATA_COMPRESSION = ' + CompressionMode + ')
' + CASE WHEN tc.Constraint_Name IS NULL THEN '' ELSE 'ALTER TABLE [' + @TargetSchemaName + '].[' + @TargetTableName + '] ADD CONSTRAINT ' + tc.Constraint_Name  + ' PRIMARY KEY (' + LEFT(j.List, Len(j.List)-1) + ')' END
FROM sysobjects so
INNER JOIN
(
 SELECT p.object_id, MIN(data_compression_desc) AS CompressionMode
 FROM sys.partitions p
 WHERE p.object_id = @TableId
 AND p.index_id < 2
 GROUP BY p.object_id
) p ON p.object_id = so.id
CROSS APPLY
(
 SELECT '  [' + column_name + '] ' + data_type + 
  CASE data_type
            WHEN 'sql_variant' THEN ''
            WHEN 'text' THEN ''
            WHEN 'decimal' THEN '(' + cast(numeric_precision_radix AS VARCHAR) + ', ' + CAST(numeric_scale AS VARCHAR) + ')'
            ELSE COALESCE('('+ CASE WHEN character_maximum_length = -1 THEN 'MAX' ELSE CAST(character_maximum_length AS VARCHAR) END +')', '')
   END + ' ' +
        CASE
   WHEN EXISTS
    ( 
     SELECT id FROM syscolumns
     WHERE object_name(id) = so.name
     AND name = column_name
     AND columnproperty(id,name, 'IsIdentity') = 1 
    )
    THEN 'IDENTITY(' + CAST(IDENT_SEED(so.name) AS VARCHAR) + ', ' + CAST(IDENT_INCR(so.name) AS VARCHAR) + ') '
   ELSE ''
   END +
         (CASE WHEN IS_NULLABLE = 'No' THEN 'NOT ' ELSE '' END ) + 'NULL' + 
          CASE WHEN information_schema.columns.COLUMN_DEFAULT IS NOT NULL THEN ' DEFAULT '+ information_schema.columns.COLUMN_DEFAULT ELSE '' END + ',' + CHAR(10)
     FROM information_schema.columns
     WHERE table_name = so.name
     ORDER BY ordinal_position
     FOR XML PATH('')
) o (list)
LEFT JOIN information_schema.table_constraints tc
 ON tc.Table_name = so.Name AND tc.Constraint_Type = 'PRIMARY KEY'
CROSS APPLY
(
 SELECT '[' + Column_Name + '], '
 FROM information_schema.key_column_usage kcu
 WHERE kcu.Constraint_Name = tc.Constraint_Name
 ORDER BY ORDINAL_POSITION
 FOR XML PATH('')
) j (list)
WHERE so.xtype = 'U'
AND so.name NOT IN ('dtproperties')
AND so.id = @TableId

SET @OutputQuery = @OutputQuery + @SqlQuery_CreateTable



/* ******************************** */
/* GENERATE CREATE INDEX STATEMENTS */
/* ******************************** */
IF @ScriptIndexes = 1
 BEGIN
 DECLARE @SqlQuery_CreateIndex VARCHAR(MAX)
 ;
 WITH IndexCTE AS
 (
  SELECT DISTINCT
   i.index_id,
   i.name,
   i.object_id,
   p.[data_compression_desc] COLLATE SQL_Latin1_General_CP1_CI_AS AS CompressionMode,
   ifg.IndexFilegroup,
   i.is_unique
  FROM sys.indexes i
  INNER JOIN sys.tables t ON t.object_id = i.object_id
  INNER JOIN sys.schemas s ON t.schema_id = s.schema_id
  INNER JOIN sys.index_columns ic ON i.index_id = ic.index_id AND i.object_id = ic.object_id
  INNER JOIN
  (
   SELECT p.object_id, p.index_id, MIN(p.[data_compression_desc]) AS [data_compression_desc]
   FROM sys.partitions p
   GROUP BY p.object_id, p.index_id
  ) p ON p.index_id = i.index_id AND p.object_id = t.object_id
  INNER JOIN /* Find the filegroup or partition scheme on which the index relies */
  (
   SELECT i.index_id, i.name, '[' + ps.name + ']([' + c.name + '])' AS IndexFilegroup
   FROM sys.tables t
   INNER JOIN sys.schemas s ON s.schema_id = t.schema_id
   INNER JOIN sys.indexes i ON i.object_id = t.object_id
   INNER JOIN sys.partition_schemes ps ON ps.data_space_id = i.data_space_id
   INNER JOIN sys.partition_functions pf ON pf.function_id = ps.function_id
   INNER JOIN sys.index_columns ic ON ic.partition_ordinal > 0 AND ic.index_id = i.index_id AND ic.object_id = t.object_id
   INNER JOIN sys.columns c ON c.object_id = ic.object_id AND c.column_id = ic.column_id
   WHERE 1 = 1
   AND s.name = @OriginalSchemaName
   AND t.name = @OriginalTableName
  UNION ALL
   SELECT i.index_id, i.name, '[' + d.name + ']' AS IndexFilegroup
   FROM sys.filegroups d
   INNER JOIN sys.indexes i ON i.data_space_id = d.data_space_id
   INNER JOIN sys.tables t ON t.object_id = i.object_id
   WHERE 1 = 1
   AND t.name = @OriginalTableName
   AND t.schema_id = schema_id(@OriginalSchemaName)
  ) ifg ON ifg.index_id = p.index_id
  WHERE EXISTS
  (
   SELECT *
   FROM sys.columns c
   WHERE c.column_id = ic.column_id
   AND c.object_id = ic.object_id
  )
  AND t.name = @OriginalTableName
  AND s.name = @OriginalSchemaName
 ), 
 IndexCTE2 AS
 (
  SELECT 
   IndexCTE.name AS IndexName,
   CASE IndexCTE.is_unique WHEN 1 THEN 'UNIQUE ' ELSE '' END AS IndexUnicity,
   CASE IndexCTE.index_id WHEN 1 THEN 'CLUSTERED' ELSE 'NONCLUSTERED' END AS IndexType,
   (
    SELECT CHAR(10) + '  ' + c.name + CASE ic.is_descending_key WHEN 0 THEN ' ASC' ELSE ' DESC' END + ','
    FROM sys.columns c
    INNER JOIN sys.index_columns ic
     ON c.object_id = ic.object_id
     AND ic.column_id = c.column_id
     AND ic.Is_Included_Column = 0
    WHERE IndexCTE.OBJECT_ID = ic.object_id
    AND IndexCTE.index_id = ic.index_id
    AND ic.key_ordinal > 0
    ORDER BY key_ordinal
    FOR XML PATH('')
   ) ixcols,
   ISNULL(
   (
    SELECT DISTINCT CHAR(10) + '  ' + c.name + ','
    FROM sys.columns c
    INNER JOIN sys.index_columns ic
     ON c.object_id = ic.object_id
     AND ic.column_id = c.column_id
     AND ic.Is_Included_Column = 1
    WHERE IndexCTE.OBJECT_ID = ic.object_id 
    AND IndexCTE.index_id = ic.index_id 
    FOR XML PATH('')
   ), '') includedcols,
   IndexCTE.index_id,
   IndexCTE.CompressionMode,
   IndexCTE.IndexFilegroup
  FROM indexCTE
 ),
 CreateSingleIndexQuery AS
 ( 
 SELECT 
  'CREATE ' + IndexUnicity + IndexType + ' INDEX [' + IndexName + '] ON [' + @TargetSchemaName + '].[' + @TargetTableName + ']' + CHAR(10) +
  '(' + SUBSTRING(ixcols, 1, LEN(ixcols) - 1) + CHAR(10) +
  CASE LEN(includedcols)
   WHEN 0 THEN ')'
   ELSE ')' + CHAR(10) + 'INCLUDE' + CHAR(10) + '(' + SUBSTRING(includedcols, 1, LEN(includedcols) - 1) + CHAR(10) + ')'
  END + CHAR(10) +
  'WITH ( DATA_COMPRESSION = ' + CompressionMode + ' )' + CHAR(10) +
  'ON ' + IndexFilegroup AS Query,
  index_id
 FROM IndexCTE2
 )
 SELECT @SqlQuery_CreateIndex = o.list
 FROM CreateSingleIndexQuery
 CROSS APPLY
 (
  SELECT CHAR(10) + Query + CHAR(10)
  FROM CreateSingleIndexQuery
  ORDER BY index_id
  FOR XML PATH('')
 ) o (list)


 SET @OutputQuery = @OutputQuery + @SqlQuery_CreateIndex
 END


END TRY

BEGIN CATCH
  -- Raise an error with the details of the exception
  DECLARE @ErrMsg nvarchar(4000), @ErrSeverity int
  SELECT @ErrMsg = ERROR_MESSAGE(),
         @ErrSeverity = ERROR_SEVERITY()

  RAISERROR(@ErrMsg, @ErrSeverity, 1)
END CATCH

END

Easy to use:
DECLARE @SqlQuery VARCHAR(4000) = ''
EXEC SPR_SCRIPT_CREATE_TABLE
  'dbo', 'existing_table',
  'dbo', 'switch_table',
  @SqlQuery OUTPUT

EXEC(@SqlQuery)

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