Collect Index Usage Statistics.sql

-----------------------------------------------------------
-- Name: CollectIndexUsageStats.sql
--
-- Description: Collects index usage statistics over time.
-- Schedule a job to run dbo.CollectIndexUsageStats once a
-- day after midnight to collect daily Index Usage Stats
-- The job named A DBA Collect Index Daily Usage Statistics
-- does what it needs
-----------------------------------------------------------


USE [AdminTools];
GO

-- stores cumulative data from sys.dm_db_index_usage_stats DMV
CREATE TABLE [dbo].[IndexUsageStats_LastCumulative] (
	[ServerNameID] [int] NOT NULL,
	[DatabaseID] [smallint] NOT NULL,
	[ObjectID] [int] NOT NULL,
	[IndexID] [int] NOT NULL,
	[LoadTime] [datetime2](0) NOT NULL,
	[User_Seeks] [bigint] NOT NULL,
	[User_Scans] [bigint] NOT NULL,
	[User_Lookups] [bigint] NOT NULL,
	[User_Updates] [bigint] NOT NULL,
	[System_Seeks] [bigint] NOT NULL,
	[System_Scans] [bigint] NOT NULL,
	[System_Lookups] [bigint] NOT NULL,
	[System_Updates] [bigint] NOT NULL,
	CONSTRAINT [PK_IUS_C] PRIMARY KEY CLUSTERED ([ServerNameID],[DatabaseID],[ObjectID],[IndexID])
);
GO

-- used for Server/DB/Schema/Table/Index name mapping
CREATE TABLE [dbo].[Names] (
	[ID] [int] IDENTITY(1,1) NOT NULL,
	[Value] [nvarchar](260) NOT NULL,
	CONSTRAINT [PK_Names] PRIMARY KEY CLUSTERED ([ID])
);
GO

-- stores historical usage statistics
CREATE TABLE [dbo].[IndexUsageStats] (
	[StatsDate] [datetime2](0) NOT NULL,
	[ServerNameID] [int] NOT NULL,
	[DatabaseID] [smallint] NOT NULL,
	[ObjectID] [int] NOT NULL,
	[IndexID] [int] NOT NULL,
	[DatabaseNameID] [int] NOT NULL,
	[SchemaNameID] [int] NOT NULL,
	[TableNameID] [int] NOT NULL,
	[IndexNameID] [int] NULL,
	[User_Seeks] [bigint] NOT NULL,
	[User_Scans] [bigint] NOT NULL,
	[User_Lookups] [bigint] NOT NULL,
	[User_Updates] [bigint] NOT NULL,
	[System_Seeks] [bigint] NOT NULL,
	[System_Scans] [bigint] NOT NULL,
	[System_Lookups] [bigint] NOT NULL,
	[System_Updates] [bigint] NOT NULL,
	CONSTRAINT [PK_IUS] PRIMARY KEY CLUSTERED ([StatsDate],[ServerNameID],[DatabaseID],[ObjectID],[IndexID]),
	CONSTRAINT [FK_IUS_Names_DB] FOREIGN KEY([DatabaseNameID]) REFERENCES [dbo].[Names] ([ID]),
	CONSTRAINT [FK_IUS_Names_Index] FOREIGN KEY([IndexNameID]) REFERENCES [dbo].[Names] ([ID]),
	CONSTRAINT [FK_IUS_Names_Schema] FOREIGN KEY([SchemaNameID]) REFERENCES [dbo].[Names] ([ID]),
	CONSTRAINT [FK_IUS_Names_Table] FOREIGN KEY([TableNameID]) REFERENCES [dbo].[Names] ([ID]),
	CONSTRAINT [CK_IUS_PositiveValues] CHECK ([User_Seeks]>=(0) AND [User_Scans]>=(0) AND [user_Lookups]>=(0)
		AND [user_updates]>=(0) AND [system_seeks]>=(0) AND [system_scans]>=(0) AND [system_lookups]>=(0)
		AND [system_updates]>=(0))
);
GO

-- collects usage statistics
-- I run this once daily (can be run more often if you like)
CREATE PROCEDURE [dbo].[CollectIndexUsageStats]
AS
BEGIN
	BEGIN TRY
		SET NOCOUNT ON;

		-- get current stats for all online databases

		SELECT database_id, name
		INTO #dblist
		FROM sys.databases
		WHERE [state] = 0
			AND database_id != 2; -- skip TempDB

		CREATE TABLE #t (
			StatsDate DATETIME2(0),
			ServerName SYSNAME,
			DatabaseID SMALLINT,
			ObjectID INT,
			IndexID INT,
			DatabaseName SYSNAME,
			SchemaName SYSNAME,
			TableName SYSNAME,
			IndexName SYSNAME NULL,
			User_Seeks BIGINT,
			User_Scans BIGINT,
			User_Lookups BIGINT,
			User_Updates BIGINT,
			System_Seeks BIGINT,
			System_Scans BIGINT,
			System_Lookups BIGINT,
			System_Updates BIGINT
		);

		DECLARE @DBID INT;
		DECLARE @DBNAME SYSNAME;
		DECLARE @Qry NVARCHAR(2000);

		-- iterate through each DB, generate & run query
		WHILE (SELECT COUNT(*) FROM #dblist) > 0
		BEGIN
			SELECT TOP (1) @DBID=database_id, @DBNAME=[name]
			FROM #dblist ORDER BY database_id;

			SET @Qry = '
				INSERT INTO #t
				SELECT
					SYSDATETIME() AS StatsDate,
					@@SERVERNAME AS ServerName,
					s.database_id AS DatabaseID,
					s.object_id AS ObjectID,
					s.index_id AS IndexID,
					''' + @DBNAME + ''' AS DatabaseName,
					c.name AS SchemaName,
					o.name AS TableName,
					i.name AS IndexName,
					s.user_seeks,
					s.user_scans,
					s.user_lookups,
					s.user_updates,
					s.system_seeks,
					s.system_scans,
					s.system_lookups,
					s.system_updates
				FROM sys.dm_db_index_usage_stats s
				INNER JOIN ' + @DBNAME + '.sys.objects o ON s.object_id = o.object_id
				INNER JOIN ' + @DBNAME + '.sys.schemas c ON o.schema_id = c.schema_id
				INNER JOIN ' + @DBNAME + '.sys.indexes i ON s.object_id = i.object_id and s.index_id = i.index_id
				WHERE s.database_id = ' + CONVERT(NVARCHAR,@DBID) + ';
				';

			EXEC sp_executesql @Qry;

			DELETE FROM #dblist WHERE database_id = @DBID;
		END -- db while loop

		DROP TABLE #DBList;

		BEGIN TRAN;

		-- create ids for Server Name by inserting new ones into dbo.Names
		INSERT INTO AdminTools.dbo.Names (Value)
		SELECT DISTINCT RTRIM(LTRIM(t.ServerName)) AS ServerName
		FROM #t t
		LEFT JOIN AdminTools.dbo.Names n ON t.ServerName = n.Value
		WHERE n.ID IS NULL AND t.ServerName IS NOT NULL
		ORDER BY RTRIM(LTRIM(t.ServerName));

		-- same as above for DatabaseName
		INSERT INTO AdminTools.dbo.Names (Value)
		SELECT DISTINCT RTRIM(LTRIM(t.DatabaseName)) AS DatabaseName
		FROM #t t
		LEFT JOIN AdminTools.dbo.Names n ON t.DatabaseName = n.Value
		WHERE n.ID IS NULL AND t.DatabaseName IS NOT NULL
		ORDER BY RTRIM(LTRIM(t.DatabaseName));

		-- SchemaName
		INSERT INTO AdminTools.dbo.Names (Value)
		SELECT DISTINCT RTRIM(LTRIM(t.SchemaName)) AS SchemaName
		FROM #t t
		LEFT JOIN AdminTools.dbo.Names n ON t.SchemaName = n.Value
		WHERE n.ID IS NULL AND t.SchemaName IS NOT NULL
		ORDER BY RTRIM(LTRIM(t.SchemaName));

		-- TableName
		INSERT INTO AdminTools.dbo.Names (Value)
		SELECT DISTINCT RTRIM(LTRIM(t.TableName)) AS TableName
		FROM #t t
		LEFT JOIN AdminTools.dbo.Names n ON t.TableName = n.Value
		WHERE n.ID IS NULL AND t.TableName IS NOT NULL
		ORDER BY RTRIM(LTRIM(t.TableName));

		-- IndexName
		INSERT INTO AdminTools.dbo.Names (Value)
		SELECT DISTINCT RTRIM(LTRIM(t.IndexName)) AS IndexName
		FROM #t t
		LEFT JOIN AdminTools.dbo.Names n ON t.IndexName = n.Value
		WHERE n.ID IS NULL AND t.IndexName IS NOT NULL
		ORDER BY RTRIM(LTRIM(t.IndexName));

		-- Calculate Deltas
		INSERT INTO AdminTools.dbo.IndexUsageStats (StatsDate, ServerNameID, DatabaseID, ObjectID,
			IndexID, DatabaseNameID, SchemaNameID, TableNameID, IndexNameID, User_Seeks, User_Scans,
			User_Lookups, User_Updates, System_Seeks, System_Scans, System_Lookups, System_Updates)
		SELECT
			t.StatsDate,
			s.ID AS ServerNameID,
			t.DatabaseID,
			t.ObjectID,
			t.IndexID,
			d.ID AS DatabaseNameID,
			c.ID AS SchemaNameID,
			b.ID AS TableNameID,
			i.ID AS IndexNameID,
			CASE
				-- if the previous cumulative value is greater than the current one, the server has been reset
				-- just use the current value
				WHEN t.User_Seeks - ISNULL(lc.User_Seeks,0) < 0 THEN t.User_Seeks
				-- if the prev value is less than the current one, then subtract to get the delta
				ELSE t.User_Seeks - ISNULL(lc.User_Seeks,0)
			END AS User_Seeks,
			CASE
				WHEN t.User_Scans - ISNULL(lc.User_Scans,0) < 0 THEN t.User_Scans
				ELSE t.User_Scans - ISNULL(lc.User_Scans,0)
			END AS User_Scans,
			CASE
				WHEN t.User_Lookups - ISNULL(lc.User_Lookups,0) < 0 THEN t.User_Lookups
				ELSE t.User_Lookups - ISNULL(lc.User_Lookups,0)
			END AS User_Lookups,
			CASE
				WHEN t.User_Updates - ISNULL(lc.User_Updates,0) < 0 THEN t.User_Updates
				ELSE t.User_Updates - ISNULL(lc.User_Updates,0)
			END AS User_Updates,
			CASE
				WHEN t.System_Seeks - ISNULL(lc.System_Seeks,0) < 0 THEN t.System_Seeks
				ELSE t.System_Seeks - ISNULL(lc.System_Seeks,0)
			END AS System_Seeks,
			CASE
				WHEN t.System_Scans - ISNULL(lc.System_Scans,0) < 0 THEN t.System_Scans
				ELSE t.System_Scans - ISNULL(lc.System_Scans,0)
			END AS System_Scans,
			CASE
				WHEN t.System_Lookups - ISNULL(lc.System_Lookups,0) < 0 THEN t.System_Lookups
				ELSE t.System_Lookups - ISNULL(lc.System_Lookups,0)
			END AS System_Lookups,
			CASE
				WHEN t.System_Updates - ISNULL(lc.System_Updates,0) < 0 THEN t.System_Updates
				ELSE t.System_Updates - ISNULL(lc.System_Updates,0)
			END AS System_Updates
		FROM #t t
		INNER JOIN AdminTools.dbo.Names s ON t.ServerName = s.Value
		INNER JOIN AdminTools.dbo.Names d ON t.DatabaseName = d.Value
		INNER JOIN AdminTools.dbo.Names c ON t.SchemaName = c.Value
		INNER JOIN AdminTools.dbo.Names b ON t.TableName = b.Value
		LEFT JOIN AdminTools.dbo.Names i ON t.IndexName = i.Value
		LEFT JOIN AdminTools.dbo.IndexUsageStats_LastCumulative lc
			ON s.ID = lc.ServerNameID
			AND t.DatabaseID = lc.DatabaseID
			AND t.ObjectID = lc.ObjectID
			AND t.IndexID = lc.IndexID
		ORDER BY StatsDate, ServerName, DatabaseID, ObjectID, IndexID;

		-- Update last cumulative values with the current ones
		MERGE INTO AdminTools.dbo.IndexUsageStats_LastCumulative lc
		USING #t t
		INNER JOIN AdminTools.dbo.Names s ON t.ServerName = s.Value
		ON s.ID = lc.ServerNameID
			AND t.DatabaseID = lc.DatabaseID
			AND t.ObjectID = lc.ObjectID
			AND t.IndexID = lc.IndexID
		WHEN MATCHED THEN
			UPDATE SET
				lc.LoadTime = t.StatsDate,
				lc.User_Seeks = t.User_Seeks,
				lc.User_Scans = t.User_Scans,
				lc.User_Lookups = t.User_Lookups,
				lc.User_Updates = t.User_Updates,
				lc.System_Seeks = t.System_Seeks,
				lc.System_Scans = t.System_Scans,
				lc.System_Lookups = t.System_Lookups,
				lc.System_Updates = t.System_Updates
		WHEN NOT MATCHED BY TARGET THEN
			INSERT (ServerNameID, DatabaseID, ObjectID, IndexID, LoadTime, User_Seeks, User_Scans,
				User_Lookups, User_Updates, System_Seeks, System_Scans,
				System_Lookups, System_Updates)
			VALUES (s.ID, t.DatabaseID, t.ObjectID, t.IndexID, t.StatsDate, t.User_Seeks, t.User_Scans,
				t.User_Lookups, t.User_Updates, t.System_Seeks, t.System_Scans,
				t.System_Lookups, t.System_Updates)
		WHEN NOT MATCHED BY SOURCE
			THEN DELETE;

		COMMIT TRAN;

	END TRY
	BEGIN CATCH

		IF @@TRANCOUNT > 0
			ROLLBACK TRAN;

		DECLARE @ErrorNumber INT;
		DECLARE @ErrorSeverity INT;
		DECLARE @ErrorState INT;
		DECLARE @ErrorProcedure NVARCHAR(126);
		DECLARE @ErrorLine INT;
		DECLARE @ErrorMessage NVARCHAR(2048);

		SELECT @ErrorNumber = ERROR_NUMBER(),
			   @ErrorSeverity = ERROR_SEVERITY(),
			   @ErrorState = ERROR_STATE(),
			   @ErrorProcedure = ERROR_PROCEDURE(),
			   @ErrorLine = ERROR_LINE(),
			   @ErrorMessage = ERROR_MESSAGE();

		RAISERROR (@ErrorMessage, @ErrorSeverity, @ErrorState);

	END CATCH
END
GO

-- displays usage statistics
CREATE VIEW [dbo].[vw_IndexUsageStats]
AS
SELECT
	s.StatsDate,
	vn.Value AS ServerName,
	dbn.Value AS DatabaseName,
	sn.Value AS SchemaName,
	tn.Value AS TableName,
	dn.Value AS IndexName,
	s.IndexID,
	s.User_Seeks,
	s.User_Scans,
	s.User_Lookups,
	s.User_Updates,
	s.System_Seeks,
	s.System_Scans,
	s.System_Lookups,
	s.System_Updates
FROM dbo.IndexUsageStats s
INNER JOIN dbo.Names vn ON s.ServerNameID = vn.ID
INNER JOIN dbo.Names dbn ON s.DatabaseNameID = dbn.ID
INNER JOIN dbo.Names sn ON s.SchemaNameID = sn.ID
INNER JOIN dbo.Names tn ON s.TableNameID = tn.ID
LEFT JOIN dbo.Names dn ON s.IndexNameID = dn.ID;
GO