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Use existing non-clustered index usage stats, and missing index stats, to generate clustered-index recommendations for heap tables (more info: https://eitanblumin.com/2019/12/30/resolving-tables-without-clustered-indexes-heaps/ )
-------------------------------------------------------
------ Generate Clustered Index Recommendations -------
-------------------------------------------------------
-- Author: Eitan Blumin | https://www.eitanblumin.com
-- More info: https://eitanblumin.com/2019/12/30/resolving-tables-without-clustered-indexes-heaps/
-------------------------------------------------------
-- Description:
-- ------------
-- This script finds all heap tables, and "guestimates" a clustered index recommendation for each.
-- The script implements the following algorithm:
--
-- 1. Look in index usage stats for the most "popular" non-clustered indexes which would be a good candidate as clustered index, give priority to UNIQUE indexes. If no such was found, then:
-- 2. If there's any non-clustered index at all, get the first one created with the highest number of INCLUDE columns, give priority to UNIQUE indexes. If no such was found, then:
-- 3. Look in missing index stats for the most impactful index that has the highest number of INCLUDE columns. If no such was found, then:
-- 4. Use the IDENTITY column in the table. If no such was found, then:
-- 5. Check for any column statistics in the table and look for the column which is the most selective (most unique values). If no such was found, then:
-- 6. Use the first date/time column in the table, give priority to columns with a default constraint. If no such was found, then:
-- 7. Use the first int/bigint/smallint/tinyint column in the table, give priority to columns without a default constraint. If no such was found, then:
-- 8. Use the first non-nullable column in the table, give priority to columns without a default constraint. If no such was found, then:
-- 9. Bummer. I'm out of ideas. No recommendations are possible.
-------------------------------------------------------
-- Change log:
-- ------------
-- 2021-08-29 Changed INT to BIGINT to support larger tables
-- 2021-08-18 Added last read/write details per table
-- 2021-08-16 Fixed missing database context bug and some code quality issues.
-- 2021-04-18 Added enhancements for replacing primary key, and added parameter @DefaultClusteredIndexName
-- 2021-03-21 Fixed DROP command for unique or primary key constraints; added check for deprecated data types; some other minor fixes
-- 2021-02-15 Added details and logic based on index used pages count
-- 2020-11-25 Various improvements:
-- - Changed recommendations prioritization - gave higher priority to most SELECTIVE column
-- - Added parameter @RetainHighestCompression to retain DATA_COMPRESSION settings in scripts
-- - Ignore special index types (columnstore, XML, spatial, ...), and hypothetical indexes
-- - Give priority to UNIQUE indexes when prioritizing existing indexes based on usage stats
-- - Replaced usage of sp_MSforeachDb with a cursor, to support longer command text
-- 2020-11-18 Added Rollback_Script column in output
-- 2020-11-03 Added new step to find first integer column, and a new step to find first non-nullable column
-- 2020-09-30 Added optional parameters @OnlineRebuild, @SortInTempDB, @MaxDOP
-- 2020-09-21 Added columns list in initial recommendations retrieval, removed newlines from remediation scripts
-- 2020-07-14 Added proper support for replacing unique indexes
-- 2020-07-14 Added generated script for replacing existing nc index with a clustered index
-- 2020-02-19 Added support for Azure SQL DB, and added version-dependent check to ignore memory optimized tables
-- 2020-02-12 Changed prioritization a bit for the recommendations, added automatic generation of basic CREATE script
-- 2020-01-07 Added check of database Updateability, and moved around a few columns
-- 2019-12-29 Added checks for IDENTITY columns, and first DATE/TIME columns
-- 2019-12-23 First version
-------------------------------------------------------
-- Parameters:
-- ------------
DECLARE
@MinimumRowsInTable BIGINT = 200000 -- Minimum number of rows in a table in order to check it
-- Parameters controlling the structure of output scripts:
,@OnlineRebuild BIT = 1 -- If 1, will generate CREATE INDEX commands with the ONLINE option turned on.
,@SortInTempDB BIT = 1 -- If 1, will generate CREATE INDEX commands with the SORT_IN_TEMPDB option turned on.
,@MaxDOP INT = NULL -- If not NULL, will generate CREATE INDEX commands with the MAXDOP option. Set to 1 to prevent parallelism and reduce workload.
,@RetainHighestCompression BIT = 1 -- If 1, will retain the highest data compression setting when replacing existing indexes
,@DefaultClusteredIndexName SYSNAME = N'IX_clust_{TableName}_{KeyColumns}' -- Default name for entirely new indexes. Supported placeholders: {TableName} , {KeyColumns}
-------------------------------------------------------
SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;
SET NOCOUNT, ARITHABORT, XACT_ABORT ON;
IF OBJECT_ID(N'tempdb..#temp_heap') IS NOT NULL DROP TABLE #temp_heap;
DECLARE @CMD NVARCHAR(MAX), @CurrDB SYSNAME, @CurrObjId INT, @CurrTable NVARCHAR(1000);
DECLARE @RebuildOptions NVARCHAR(MAX);
DECLARE @spExecuteSql NVARCHAR(1000)
-- Init local variables and defaults
SET @RebuildOptions = N''
IF @OnlineRebuild = 1 SET @RebuildOptions = @RebuildOptions + N', ONLINE = {ONLINE_ON}'
IF @SortInTempDB = 1 SET @RebuildOptions = @RebuildOptions + N', SORT_IN_TEMPDB = ON'
IF @MaxDOP IS NOT NULL SET @RebuildOptions = @RebuildOptions + N', MAXDOP = ' + CONVERT(nvarchar(4000), @MaxDOP)
IF @RetainHighestCompression = 1 SET @RebuildOptions = @RebuildOptions + N', DATA_COMPRESSION = {COMPRESSION}'
IF @RebuildOptions LIKE N',%' SET @RebuildOptions = N' WITH (' + STUFF(@RebuildOptions, 1, 2, N'') + N')';
IF @OnlineRebuild = 1 AND ISNULL(CONVERT(int, SERVERPROPERTY('EngineEdition')),0) NOT IN (3,5,8)
BEGIN
RAISERROR(N'-- WARNING: @OnlineRebuild is set to 1, but current SQL edition does not support ONLINE rebuilds.', 0, 1);
END
CREATE TABLE #temp_heap
(
[database_name] SYSNAME NOT NULL,
table_name SYSNAME NOT NULL,
full_table_name NVARCHAR(1000) NOT NULL,
num_of_rows BIGINT NULL,
heap_used_pages BIGINT NULL,
[object_id] INT NULL,
candidate_index SYSNAME NULL,
candidate_index_used_pages BIGINT NULL,
candidate_columns_from_existing_index NVARCHAR(MAX) NULL,
include_columns_from_existing_index NVARCHAR(MAX) NULL,
candidate_columns_from_missing_index NVARCHAR(MAX) NULL,
identity_column SYSNAME NULL,
most_selective_column_from_stats SYSNAME NULL,
first_date_column SYSNAME NULL,
first_integer_column SYSNAME NULL,
first_integer_column_type SYSNAME NULL,
first_non_nullable_column SYSNAME NULL,
is_unique BIT NULL,
is_primary_key BIT NULL,
is_constraint BIT NULL,
has_non_online_columns BIT NULL,
data_compression_type TINYINT NULL,
data_compression_type_desc AS (CASE data_compression_type WHEN 2 THEN 'PAGE' WHEN 1 THEN 'ROW' ELSE 'NONE' END)
);
SET @CMD = N'
SELECT DB_NAME() as DatabaseName, t.object_id, OBJECT_NAME(t.object_id) AS table_name, QUOTENAME(OBJECT_SCHEMA_NAME(t.object_id)) + ''.'' + QUOTENAME(OBJECT_NAME(t.object_id)) AS FullTableName
, p.total_rows
, p.total_used_page_count
, QUOTENAME(ix.name) AS CandidateIndexName
, ix.total_used_page_count
, ix_columns
, inc_columns
, ix.is_unique
, ix.is_primary_key
, ix.is_constraint
, has_non_online_columns = CASE WHEN EXISTS (
SELECT TOP 1 1 FROM sys.columns AS c
WHERE c.object_id = t.object_id
AND system_type_id IN (SELECT system_type_id FROM sys.types WHERE name IN (''image'',''text'',''ntext''))
) THEN 1 ELSE 0 END
, p.max_data_compression
FROM sys.tables t
CROSS APPLY
(
SELECT SUM(p.rows) AS total_rows, MAX(p.data_compression) AS max_data_compression, SUM(ps.used_page_count) AS total_used_page_count
FROM sys.partitions AS p
INNER JOIN sys.dm_db_partition_stats AS ps
ON ps.index_id = p.index_id AND ps.object_id = p.object_id AND p.partition_id = ps.partition_id
WHERE t.object_id = p.OBJECT_ID
AND p.index_id = 0
' + ISNULL(N'HAVING SUM(p.rows) >= ' + CONVERT(NVARCHAR(MAX),@MinimumRowsInTable), N'') + N'
) AS p
OUTER APPLY
(
SELECT TOP 1 us.index_id, ix.[name], ix.is_unique, ix.is_primary_key, pstat.total_used_page_count
, is_constraint = CASE WHEN 1 IN (ix.is_primary_key, ix.is_unique_constraint) THEN 1 ELSE 0 END
FROM sys.dm_db_index_usage_stats AS us
INNER JOIN sys.indexes AS ix
ON us.index_id = ix.index_id AND us.object_id = ix.object_id
CROSS APPLY
(
SELECT SUM(used_page_count) AS total_used_page_count
FROM sys.dm_db_partition_stats AS ps
WHERE ps.index_id = ix.index_id AND ps.object_id = ix.object_id
) AS pstat
WHERE us.database_id = DB_ID()
AND us.object_id = t.object_id
AND ix.index_id > 1
AND ix.is_hypothetical = 0 AND ix.has_filter = 0
AND ix.type <= 2
ORDER BY CONVERT(tinyint, ix.is_unique) DESC, pstat.total_used_page_count ASC, us.user_updates DESC, us.user_scans DESC, us.user_seeks DESC
) AS ix
OUTER APPLY
(SELECT ix_columns = STUFF((
SELECT '', '' + QUOTENAME(COL_NAME(ic.object_id, ic.column_id)) + CASE ic.is_descending_key WHEN 1 THEN '' DESC'' ELSE '' ASC'' END
FROM sys.index_columns AS ic
WHERE ic.object_id = t.object_id AND ic.index_id = ix.index_id AND ic.is_included_column = 0
FOR XML PATH('''')
), 1, 2, '''')
, inc_columns = STUFF((
SELECT '', '' + QUOTENAME(COL_NAME(ic.object_id, ic.column_id))
FROM sys.index_columns AS ic
WHERE ic.object_id = t.object_id AND ic.index_id = ix.index_id AND ic.is_included_column = 1
FOR XML PATH('''')
), 1, 2, '''')
) AS ixcolumns
WHERE t.is_ms_shipped = 0
AND t.OBJECT_ID > 255'
-- Ignore memory-optimized tables in SQL Server versions 2014 and newer
+ CASE WHEN CONVERT(int, (@@microsoftversion / 0x1000000) & 0xff) >= 12 THEN N'
AND t.is_memory_optimized = 0'
ELSE N'' END
IF CONVERT(varchar(300),SERVERPROPERTY('Edition')) = 'SQL Azure'
BEGIN
INSERT INTO #temp_heap([database_name], [object_id], table_name, full_table_name, num_of_rows, heap_used_pages, candidate_index, candidate_index_used_pages, candidate_columns_from_existing_index, include_columns_from_existing_index, is_unique, is_primary_key, is_constraint, has_non_online_columns, data_compression_type)
exec (@CMD)
END
ELSE
BEGIN
DECLARE DBs CURSOR
LOCAL FAST_FORWARD
FOR
SELECT [name]
FROM sys.databases
WHERE database_id > 4
AND state_desc = 'ONLINE'
AND DATABASEPROPERTYEX(name, 'Updateability') = 'READ_WRITE'
OPEN DBs
FETCH NEXT FROM DBs INTO @CurrDB
WHILE @@FETCH_STATUS = 0
BEGIN
SET @spExecuteSql = QUOTENAME(@CurrDB) + N'..sp_executesql'
INSERT INTO #temp_heap([database_name], [object_id], table_name, full_table_name, num_of_rows, heap_used_pages, candidate_index, candidate_index_used_pages, candidate_columns_from_existing_index, include_columns_from_existing_index, is_unique, is_primary_key, is_constraint, has_non_online_columns, data_compression_type)
EXEC @spExecuteSql @CMD;
FETCH NEXT FROM DBs INTO @CurrDB
END
CLOSE DBs
DEALLOCATE DBs
END
-- Add recommendations based on missing index stats
UPDATE t
SET candidate_columns_from_missing_index = mi.indexColumns
FROM #temp_heap AS t
CROSS APPLY
(
SELECT TOP (1) ISNULL(mid.equality_columns, mid.inequality_columns) AS indexColumns
FROM sys.dm_db_missing_index_group_stats AS migs
INNER JOIN sys.dm_db_missing_index_groups AS mig
ON (migs.group_handle = mig.index_group_handle)
INNER JOIN sys.dm_db_missing_index_details AS mid
ON (mig.index_handle = mid.index_handle)
WHERE mid.object_id = OBJECT_ID(QUOTENAME(t.[database_name]) + N'.' + t.full_table_name) AND mid.database_id = DB_ID(t.database_name)
GROUP BY ISNULL(mid.equality_columns, mid.inequality_columns)
ORDER BY MAX(LEN(mid.included_columns) - LEN(REPLACE(mid.included_columns, ', [', ''))) DESC
, SUM(migs.avg_user_impact * migs.avg_total_user_cost) DESC
, SUM(migs.user_scans) DESC, SUM(migs.user_seeks) DESC
) AS mi
--WHERE t.candidate_index IS NULL -- filters for only those without existing recommendation
DECLARE Tabs CURSOR
LOCAL FAST_FORWARD READ_ONLY
FOR
SELECT database_name, object_id, full_table_name
FROM #temp_heap AS t
--WHERE t.candidate_columns_from_missing_index IS NULL AND t.candidate_index IS NULL -- filters for only those without existing recommendation
OPEN Tabs
FETCH NEXT FROM Tabs INTO @CurrDB, @CurrObjId, @CurrTable
WHILE @@FETCH_STATUS = 0
BEGIN
-- Get additional metadata for current table
DECLARE @FirstIndex SYSNAME, @IsUnique BIT, @IsPK BIT, @IsConstraint BIT, @HasNonOnlineColumns BIT, @IdentityColumn SYSNAME
, @FirstIndexColumns NVARCHAR(MAX), @FirstIndexIncludeColumns NVARCHAR(MAX)
, @FirstDateColumn SYSNAME, @FirstIntColumn SYSNAME, @FirstIntColumnType SYSNAME, @FirstNonNullableColumn SYSNAME;
SET @spExecuteSql = QUOTENAME(@CurrDB) + N'..sp_executesql';
SET @CMD = N'SELECT TOP 1
@FirstIndex = name,
@IsUnique = ix.is_unique,
@IsPK = ix.is_primary_key,
@IsConstraint = CASE WHEN 1 IN (ix.is_primary_key, ix.is_unique_constraint) THEN 1 ELSE 0 END,
@FirstIndexColumns =
STUFF((
SELECT '', '' + QUOTENAME(COL_NAME(ic.object_id, ic.column_id)) + CASE ic.is_descending_key WHEN 1 THEN '' DESC'' ELSE '' ASC'' END
FROM sys.index_columns AS ic
WHERE ic.object_id = ix.object_id AND ic.index_id = ix.index_id AND ic.is_included_column = 0
FOR XML PATH('''')
), 1, 2, ''''),
@FirstIndexIncludeColumns =
STUFF((
SELECT '', '' + QUOTENAME(COL_NAME(ic.object_id, ic.column_id))
FROM sys.index_columns AS ic
WHERE ic.object_id = ix.object_id AND ic.index_id = ix.index_id AND ic.is_included_column = 1
FOR XML PATH('''')
), 1, 2, '''')
FROM sys.indexes AS ix
OUTER APPLY (SELECT SUM(CASE WHEN is_included_column = 1 THEN 1 ELSE 0 END) AS included_columns, COUNT(*) AS indexed_columns
FROM sys.index_columns AS ic WHERE ic.object_id = ix.object_id AND ic.index_id = ix.index_id) AS st
WHERE object_id = @ObjId AND index_id > 0
AND is_hypothetical = 0 AND ix.has_filter = 0
AND type <= 2 -- ignore special index types
ORDER BY ix.is_unique DESC, included_columns DESC, indexed_columns ASC, index_id ASC;
SELECT @IdentityColumn = [name]
FROM sys.identity_columns
WHERE object_id = @ObjId;
SELECT TOP 1 @FirstDateColumn = c.[name]
FROM sys.columns AS c
LEFT JOIN sys.default_constraints AS dc
ON c.default_object_id = dc.object_id
AND c.object_id = dc.parent_object_id
WHERE c.object_id = @ObjId
AND c.system_type_id IN
(SELECT system_type_id FROM sys.types WHERE precision > 0 AND (name LIKE ''%date%'' OR name LIKE ''%time%''))
ORDER BY
CASE WHEN dc.[definition] IS NOT NULL THEN 0 ELSE 1 END ASC,
CONVERT(smallint, c.is_nullable) ASC,
c.column_id ASC;
SELECT TOP 1 @FirstIntColumn = c.[name], @FirstIntColumnType = t.[name]
FROM sys.columns AS c
LEFT JOIN sys.default_constraints AS dc
ON c.default_object_id = dc.object_id
AND c.object_id = dc.parent_object_id
LEFT JOIN sys.types AS t ON c.system_type_id = t.system_type_id
WHERE c.object_id = @ObjId
AND t.[name] IN (''bigint'', ''int'', ''smallint'', ''tinyint'')
AND c.is_nullable = 0
ORDER BY
CASE WHEN dc.[definition] IS NOT NULL THEN 1 ELSE 0 END ASC,
CASE t.[name] WHEN ''int'' THEN 1 WHEN ''bigint'' THEN 2 WHEN ''smallint'' THEN 3 ELSE 4 END ASC,
c.column_id ASC;
SELECT TOP 1 @FirstNonNullableColumn = c.[name]
FROM sys.columns AS c
LEFT JOIN sys.default_constraints AS dc
ON c.default_object_id = dc.object_id
AND c.object_id = dc.parent_object_id
WHERE c.object_id = @ObjId
AND c.is_nullable = 0
ORDER BY
CASE WHEN dc.[definition] IS NOT NULL THEN 1 ELSE 0 END ASC,
c.column_id ASC;'
PRINT @CMD;
SET @FirstIndex = NULL;
SET @IsUnique = NULL;
SET @IsPK = NULL;
SET @IsConstraint = NULL;
SET @HasNonOnlineColumns = NULL;
SET @IdentityColumn = NULL;
SET @FirstDateColumn = NULL;
SET @FirstIntColumn = NULL;
SET @FirstIntColumnType = NULL;
SET @FirstNonNullableColumn = NULL;
EXEC @spExecuteSql @CMD
, N'@ObjId INT, @FirstIndex SYSNAME OUTPUT, @IsUnique BIT OUTPUT, @IsPK BIT OUTPUT, @IsConstraint BIT OUTPUT, @HasNonOnlineColumns BIT OUTPUT, @FirstIndexColumns NVARCHAR(MAX) OUTPUT, @FirstIndexIncludeColumns NVARCHAR(MAX) OUTPUT, @IdentityColumn SYSNAME OUTPUT, @FirstDateColumn SYSNAME OUTPUT, @FirstIntColumn SYSNAME OUTPUT, @FirstIntColumnType SYSNAME OUTPUT, @FirstNonNullableColumn SYSNAME OUTPUT'
, @CurrObjId, @FirstIndex OUTPUT, @IsUnique OUTPUT, @IsPK OUTPUT, @IsConstraint OUTPUT, @HasNonOnlineColumns OUTPUT, @FirstIndexColumns OUTPUT, @FirstIndexIncludeColumns OUTPUT, @IdentityColumn OUTPUT, @FirstDateColumn OUTPUT, @FirstIntColumn OUTPUT, @FirstIntColumnType OUTPUT, @FirstNonNullableColumn OUTPUT
IF @FirstIndex IS NOT NULL
BEGIN
---------------------
-- Add recommendations based on existing non-clustered indexes (even if no existing usage stats or missing index stats found)
---------------------
UPDATE #temp_heap SET candidate_index = QUOTENAME(@FirstIndex) --+ N' (no usage)'
, candidate_columns_from_existing_index = @FirstIndexColumns
, include_columns_from_existing_index = @FirstIndexIncludeColumns
, is_unique = @IsUnique
, is_primary_key = @IsPK
, is_constraint = @IsConstraint
WHERE database_name = @CurrDB AND object_id = @CurrObjId AND candidate_index IS NULL
END
IF @IdentityColumn IS NOT NULL
BEGIN
---------------------
-- Add recommendations based on identity column
---------------------
UPDATE #temp_heap SET identity_column = QUOTENAME(@IdentityColumn)
, is_unique = ISNULL(is_unique, 1)
WHERE database_name = @CurrDB AND object_id = @CurrObjId;
END
IF @FirstDateColumn IS NOT NULL
BEGIN
-- Add recommendation based on the first date/time column
UPDATE #temp_heap SET first_date_column = QUOTENAME(@FirstDateColumn)
, is_unique = ISNULL(is_unique, 0)
WHERE database_name = @CurrDB AND object_id = @CurrObjId;
END
IF @FirstIntColumn IS NOT NULL
BEGIN
-- Add recommendation based on the first integer column
UPDATE #temp_heap SET first_integer_column = QUOTENAME(@FirstIntColumn)
, first_integer_column_type = @FirstIntColumnType
, is_unique = ISNULL(is_unique, 0)
WHERE database_name = @CurrDB AND object_id = @CurrObjId;
END
IF @FirstNonNullableColumn IS NOT NULL
BEGIN
-- Add recommendation based on the first date/time column
UPDATE #temp_heap SET first_non_nullable_column = QUOTENAME(@FirstNonNullableColumn)
, is_unique = ISNULL(is_unique, 0)
WHERE database_name = @CurrDB AND object_id = @CurrObjId;
END
--IF @FirstIndex IS NULL -- Performs check only if no previous recommendations found
BEGIN
---------------------
-- Get recommendations based on most selective column based on statistics
---------------------
-- Get list of table columns
DECLARE @Columns AS TABLE (colName SYSNAME NULL);
SET @CMD = N'SELECT name FROM sys.columns WHERE object_id = @ObjId AND is_computed = 0'
INSERT INTO @Columns
EXEC @spExecuteSql @CMD, N'@ObjId INT', @CurrObjId;
-- Generate and run SHOW_STATISTICS command
SET @CMD = N'SET NOCOUNT ON;'
SELECT @CMD = @CMD + N'
BEGIN TRY
DBCC SHOW_STATISTICS(' + QUOTENAME(@CurrTable, '"') COLLATE database_default + N', ' + QUOTENAME(colName) COLLATE database_default + N') WITH DENSITY_VECTOR, NO_INFOMSGS;
END TRY
BEGIN CATCH
PRINT ERROR_MESSAGE()
END CATCH'
FROM @Columns
DECLARE @DensityStats AS TABLE (AllDensity FLOAT NULL, AvgLength FLOAT NULL, Cols NVARCHAR(MAX) NULL);
INSERT INTO @DensityStats
EXEC @spExecuteSql @CMD;
IF @@ROWCOUNT > 0
BEGIN
-- Set most selective column
UPDATE #temp_heap
SET most_selective_column_from_stats =
(
SELECT TOP (1) QUOTENAME(Cols)
FROM @DensityStats
ORDER BY AllDensity ASC, AvgLength ASC
)
, is_unique = ISNULL(is_unique, 0)
WHERE
database_name = @CurrDB
AND object_id = @CurrObjId;
END
END
-- Re-init for next iteration
DELETE @Columns;
DELETE @DensityStats;
FETCH NEXT FROM Tabs INTO @CurrDB, @CurrObjId, @CurrTable
END
CLOSE Tabs
DEALLOCATE Tabs
-- Output results
SELECT
Details = 'Database:' + QUOTENAME([database_name]) + ', Heap Table:' + full_table_name
+ COALESCE(
N', candidate INDEX: ' + t.candidate_index + ISNULL(N' (' + t.candidate_columns_from_existing_index + N')', N'')
, N', candidate column(s) from MISSING INDEX stats: ' + t.candidate_columns_from_missing_index
, N', IDENTITY column: ' + t.identity_column
, N', most SELECTIVE column: ' + t.most_selective_column_from_stats
, N', first DATE/TIME column: ' + t.first_date_column
, N', first ' + ISNULL(UPPER(t.first_integer_column_type), 'INTEGER') + ' column: ' + t.first_integer_column
, N', first non-nullable column: ' + t.first_non_nullable_column
, N', NO RECOMMENDATION POSSIBLE' + CASE WHEN ixstat.last_write_dt IS NULL AND ixstat.last_read_dt IS NULL THEN N' (likely not in use)' ELSE N'' END
)
+ CASE WHEN @OnlineRebuild = 1 AND t.has_non_online_columns = 1 THEN N'. !!! WARNING !!! ONLINE=ON not possible due to deprecated data types!' ELSE N'' END
, Script = N'USE ' + QUOTENAME(t.database_name)
+
CASE
WHEN t.candidate_index IS NOT NULL AND t.candidate_columns_from_existing_index IS NULL THEN N'; -- Recreate as clustered index: ' + t.candidate_index
WHEN t.candidate_index IS NOT NULL AND t.candidate_columns_from_existing_index IS NOT NULL THEN
CASE WHEN t.is_constraint = 1
THEN N'; ALTER TABLE ' + t.full_table_name + N' DROP CONSTRAINT ' + t.candidate_index
ELSE N'; DROP INDEX ' + t.candidate_index + ' ON ' + t.full_table_name
END
+ N'; '
+ CASE WHEN t.is_constraint = 1
THEN N'ALTER TABLE ' + t.full_table_name + N' ADD CONSTRAINT ' + t.candidate_index
+ CASE WHEN t.is_primary_key = 1 THEN N' PRIMARY KEY ' WHEN t.is_unique = 1 THEN N' UNIQUE ' ELSE N'' END
ELSE N'CREATE ' + CASE WHEN t.is_unique = 1 THEN 'UNIQUE ' ELSE N'' END + N'CLUSTERED INDEX ' + t.candidate_index + ' ON ' + t.full_table_name
END
+ N' (' + t.candidate_columns_from_existing_index + N')' + REPLACE(REPLACE(@RebuildOptions, N'{COMPRESSION}', t.data_compression_type_desc), '{ONLINE_ON}', CASE WHEN t.has_non_online_columns = 1 THEN 'OFF' ELSE 'ON' END)
ELSE
N'; CREATE ' + CASE WHEN t.is_unique = 1 THEN 'UNIQUE ' ELSE N'' END + N'CLUSTERED INDEX ' + QUOTENAME(NewClusteredIndexName) + N' ON ' + t.full_table_name
+ N' ('
+ keycolumns.KeyColumnsList
+ N')' + REPLACE(REPLACE(@RebuildOptions, N'{COMPRESSION}', t.data_compression_type_desc), '{ONLINE_ON}', CASE WHEN t.has_non_online_columns = 1 THEN 'OFF' ELSE 'ON' END)
END
, Rollback_Script = N'USE ' + QUOTENAME(t.database_name)
+
CASE
WHEN t.candidate_index IS NOT NULL AND t.candidate_columns_from_existing_index IS NULL THEN N'; -- Recreate as nonclustered index: ' + t.candidate_index
WHEN t.candidate_index IS NOT NULL AND t.candidate_columns_from_existing_index IS NOT NULL THEN N'; DROP INDEX ' + t.candidate_index + ' ON ' + t.full_table_name
+ N'; CREATE ' + CASE WHEN t.is_unique = 1 THEN 'UNIQUE ' ELSE N'' END + N'NONCLUSTERED INDEX ' + t.candidate_index + ' ON ' + t.full_table_name
+ N' (' + t.candidate_columns_from_existing_index + N')' + ISNULL(N' INCLUDE (' + t.include_columns_from_existing_index + N')', N'')
+ REPLACE(REPLACE(@RebuildOptions, N'{COMPRESSION}', t.data_compression_type_desc), '{ONLINE_ON}', CASE WHEN t.has_non_online_columns = 1 THEN 'OFF' ELSE 'ON' END)
ELSE
N'; DROP INDEX ' + QUOTENAME(NewClusteredIndexName) + N' ON ' + t.full_table_name
END
, *
FROM #temp_heap AS t
OUTER APPLY
(
SELECT KeyColumnsList = COALESCE(
t.candidate_columns_from_missing_index,
t.identity_column,
t.most_selective_column_from_stats,
t.first_date_column,
t.first_integer_column,
t.first_non_nullable_column
)
) AS keycolumns
OUTER APPLY
(
SELECT NewClusteredIndexName =
REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(
@DefaultClusteredIndexName
,N'{TableName}', t.table_name)
,N'{KeyColumns}', keycolumns.KeyColumnsList)
,N' ', N'_')
,N',', N'')
,N']', N'')
,N'[', N'')
) AS ixname
OUTER APPLY
(
SELECT max(stat.last_write_dt), max(stat.last_read_dt)
FROM sys.dm_db_index_usage_stats AS us
CROSS APPLY
(VALUES
(us.last_system_update, us.last_system_lookup),
(us.last_user_update, us.last_system_scan),
(NULL, us.last_system_seek),
(NULL, us.last_user_lookup),
(NULL, us.last_user_scan),
(NULL, us.last_user_seek)
) AS stat(last_write_dt, last_read_dt)
WHERE us.database_id = DB_ID(t.database_name)
AND us.object_id = t.object_id
) AS ixstat(last_write_dt, last_read_dt)
--DROP TABLE #temp_heap
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