May 18, 2014 at 8:39 am
Hi,
does any one have a good script to find if there are missing indexes for the must running queries first and then all other queries with run times count?
THX
May 19, 2014 at 1:36 am
hi,
I've already done that...
beside of the missing indexes how can i see the query that runs that needs this index?
May 19, 2014 at 6:50 am
I find that if I have a profiler trace representative of normal activity the queries are fairly obvious if you search on the table name, the more so the higher the effect af adding the index is calculated at. If you feed the profiler trace into the DTA one of the reports identifies the queries that benefit from the suggested indexes. You can also run one of the queries in SSMS (2008 and above) requesting the actual execution plan and info on missing indexes will be returned, enabling you to confirm you have the right query.
--This code tells you which queries are using an index
SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED
DECLARE @IndexName AS NVARCHAR(128);
set @IndexName = 'your index name';
-- Make sure the name passed is appropriately quoted
IF (LEFT(@IndexName, 1) <> '[' AND RIGHT(@IndexName, 1) <> ']') SET @IndexName = QUOTENAME(@IndexName);
--Handle the case where the left or right was quoted manually but not the opposite side
IF LEFT(@IndexName, 1) <> '[' SET @IndexName = '['+@IndexName;
IF RIGHT(@IndexName, 1) <> ']' SET @IndexName = @IndexName + ']';
-- Dig into the plan cache and find all plans using this index
;WITH XMLNAMESPACES
(DEFAULT 'http://schemas.microsoft.com/sqlserver/2004/07/showplan')
SELECT
stmt.value('(@StatementText)[1]', 'varchar(max)') AS SQL_Text,
obj.value('(@Database)[1]', 'varchar(128)') AS DatabaseName,
obj.value('(@Schema)[1]', 'varchar(128)') AS SchemaName,
obj.value('(@Table)[1]', 'varchar(128)') AS TableName,
obj.value('(@Index)[1]', 'varchar(128)') AS IndexName,
obj.value('(@IndexKind)[1]', 'varchar(128)') AS IndexKind,
cp.plan_handle,
query_plan
FROM sys.dm_exec_cached_plans AS cp
CROSS APPLY sys.dm_exec_query_plan(plan_handle) AS qp
CROSS APPLY query_plan.nodes('/ShowPlanXML/BatchSequence/Batch/Statements/StmtSimple') AS batch(stmt)
CROSS APPLY stmt.nodes('.//IndexScan/Object[@Index=sql:variable("@IndexName")]') AS idx(obj)
OPTION(MAXDOP 1, RECOMPILE);
---------------------------------------------------------------------
May 19, 2014 at 7:00 am
I have a query that uses the execution plans in cache to identify potential missing indexes[/url]. Just remember though, these are just potential candidates. You should thoroughly evaluate the recommendations.
----------------------------------------------------The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood... Theodore RooseveltThe Scary DBAAuthor of: SQL Server 2017 Query Performance Tuning, 5th Edition and SQL Server Execution Plans, 3rd EditionProduct Evangelist for Red Gate Software
May 19, 2014 at 11:03 am
At a minimum, you need to look at missing index stats and usage stats. (Beyond min, you would include sys.dm_db_index_operational_stats.)
Below are queries that will list what you need. Before running, change the bolded lines to match your requirements.
Warning: you need someone knowledgeable about indexes to interpret these results. SQL will almost always suggest many more indexes than should actually be built.
Edit: Since the missing index query can take quite a while to run, it can be cancelled by setting "@list_missing_indexes" to 0.
--!! chg to your db name
USE [<your_db_name>]
SET DEADLOCK_PRIORITY LOW --probably irrelevent, but just in case
DECLARE @list_missing_indexes bit
DECLARE @table_name_pattern sysname
SET @list_missing_indexes = 1 --1=list missing index(es); 0=don't.
--!! put your table name/name pattern here
SET @table_name_pattern = '%' --%=all tables;.
PRINT 'Started @ ' + CONVERT(varchar(30), GETDATE(), 120)
--SELECT create_date FROM sys.databases WITH (NOLOCK) WHERE name = N'tempdb'
IF @list_missing_indexes = 1
BEGIN
SELECT
GETDATE() AS capture_date,
DB_NAME(mid.database_id) AS Db_Name,
OBJECT_NAME(mid.object_id /*, mid.database_id*/) AS Table_Name,
mid.equality_columns, mid.inequality_columns, mid.included_columns,
ca1.sql_up_days AS days_in_use,
migs.*,
mid.statement, mid.object_id, mid.index_handle
FROM sys.dm_db_missing_index_details mid WITH (NOLOCK)
CROSS APPLY (
SELECT DATEDIFF(DAY, create_date, GETDATE()) AS sql_up_days FROM sys.databases WHERE name = 'tempdb'
) AS ca1
LEFT OUTER JOIN sys.dm_db_missing_index_groups mig WITH (NOLOCK) ON
mig.index_handle = mid.index_handle
LEFT OUTER JOIN sys.dm_db_missing_index_group_stats migs WITH (NOLOCK) ON
migs.group_handle = mig.index_group_handle
--order by
--DB_NAME, Table_Name, equality_columns
WHERE
1 = 1
AND mid.database_id = DB_ID()
AND OBJECT_NAME(mid.object_id) LIKE @table_name_pattern
ORDER BY
--avg_total_user_cost * (user_seeks + user_scans) DESC,
Db_Name, Table_Name, equality_columns, inequality_columns
END --IF
-- list index usage stats (seeks, scans, etc.)
SELECT
ius2.row_num, DB_NAME() AS db_name,
i.name AS index_name,
OBJECT_NAME(i.object_id/*, DB_ID()*/) AS table_name,
i.index_id, --ius.user_seeks + ius.user_scans AS total_reads,
dps.row_count,
SUBSTRING(key_cols, 3, 8000) AS key_cols, SUBSTRING(nonkey_cols, 3, 8000) AS nonkey_cols,
ius.user_seeks, ius.user_scans, ius.user_lookups, ius.user_updates,
ius.last_user_seek, ius.last_user_scan, ius.last_user_lookup, ius.last_user_update,
fk.Reference_Count AS fk_ref_count,
FILEGROUP_NAME(i.data_space_id) AS filegroup_name,
ca1.sql_up_days AS days_in_use,
ius.system_seeks, ius.system_scans, ius.system_lookups, ius.system_updates,
ius.last_system_seek, ius.last_system_scan, ius.last_system_lookup, ius.last_system_update
FROM sys.indexes i WITH (NOLOCK)
INNER JOIN sys.objects o WITH (NOLOCK) ON
o.object_id = i.object_id
CROSS APPLY (
SELECT DATEDIFF(DAY, create_date, GETDATE()) AS sql_up_days FROM sys.databases WHERE name = 'tempdb'
) AS ca1
OUTER APPLY (
SELECT
', ' + COL_NAME(object_id, ic.column_id)
FROM sys.index_columns ic
WHERE
ic.key_ordinal > 0 AND
ic.object_id = i.object_id AND
ic.index_id = i.index_id
ORDER BY
ic.key_ordinal
FOR XML PATH('')
) AS key_cols (key_cols)
OUTER APPLY (
SELECT
', ' + COL_NAME(object_id, ic.column_id)
FROM sys.index_columns ic
WHERE
ic.key_ordinal = 0 AND
ic.object_id = i.object_id AND
ic.index_id = i.index_id
ORDER BY
COL_NAME(object_id, ic.column_id)
FOR XML PATH('')
) AS nonkey_cols (nonkey_cols)
LEFT OUTER JOIN sys.dm_db_partition_stats dps WITH (NOLOCK) ON
dps.object_id = i.object_id AND
dps.index_id = i.index_id
LEFT OUTER JOIN sys.dm_db_index_usage_stats ius WITH (NOLOCK) ON
ius.database_id = DB_ID() AND
ius.object_id = i.object_id AND
ius.index_id = i.index_id
LEFT OUTER JOIN (
SELECT
database_id, object_id, MAX(user_scans) AS user_scans,
ROW_NUMBER() OVER (ORDER BY MAX(user_scans) DESC) AS row_num --user_scans|user_seeks+user_scans
FROM sys.dm_db_index_usage_stats WITH (NOLOCK)
WHERE
database_id = DB_ID()
--AND index_id > 0
GROUP BY
database_id, object_id
) AS ius2 ON
ius2.database_id = DB_ID() AND
ius2.object_id = i.object_id
LEFT OUTER JOIN (
SELECT
referenced_object_id, COUNT(*) AS Reference_Count
FROM sys.foreign_keys WITH (NOLOCK)
WHERE
is_disabled = 0
GROUP BY
referenced_object_id
) AS fk ON
fk.referenced_object_id = i.object_id
WHERE
i.object_id > 100 AND
i.is_hypothetical = 0 AND
i.type IN (0, 1, 2) AND
o.type NOT IN ( 'IF', 'IT', 'TF', 'TT' ) AND
(
o.name LIKE @table_name_pattern AND
o.name NOT LIKE 'dtprop%' AND
o.name NOT LIKE 'filestream[_]' AND
o.name NOT LIKE 'MSpeer%' AND
o.name NOT LIKE 'MSpub%' AND
--o.name NOT LIKE 'queue[_]%' AND
o.name NOT LIKE 'sys%'
)
--AND OBJECT_NAME(i.object_id, DB_ID()) IN ('tbl1', 'tbl2', 'tbl3')
ORDER BY
--row_count DESC,
--ius.user_scans DESC,
--ius2.row_num, --user_scans+user_seeks
-- list clustered index first, if any, then other index(es)
db_name, table_name, CASE WHEN i.index_id IN (0, 1) THEN 1 ELSE 2 END, index_name
PRINT 'Ended @ ' + CONVERT(varchar(30), GETDATE(), 120)
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