[Tuning] Filtered indexes...and filtered statistics.

So, SQL Server (starting with 2008) now has Filtered Indexes. Which are great - since an index is basically just a copy of the data, why copy particular fields for the entire table when you only query particular subsets of data? Add a WHERE clause to your index, and now you're querying subsets of data.


However, while reading up on it I came across this:
http://msdn.microsoft.com/en-us/library/ms190397.aspx
which introduces filtered statistics(!).

Instead of

CREATE STATISTICS BikeWeights
    ON Production.Product (Weight)

which would give you stats for the entire range, do this:

CREATE STATISTICS BikeWeights
    ON Production.Product (Weight)
WHERE ProductSubcategoryID IN (1,2,3)

which will only compute statistics for that subset of data.

DDL Triggers

We're slowly starting to roll this out, based on the below code. A very well written article; our concern is on performance.

http://www.sql-server-performance.com/articles/audit/ddl_triggers_p1.aspx


--------------------
UPDATE:
Below is the code we originally rolled out, then rolled back due to XML errors with replication (see other posts with tag DDL Triggers)

With my luck it was something stupid in my code, but I haven't gone back and looked - I'm using Event Notifications now.



--1.1 version MDB 20091119.  Removed the XML field as that's a lot of data being held for no reason.
/*
use dba_repo
If Object_ID('dba_repo.dbo.DDL_Event_Log') IS NOT NULL
DROP TABLE dbo.DDL_Event_Log
CREATE TABLE dbo.DDL_Event_Log(

ID int IDENTITY(1,1) NOT NULL,
EventTime datetime NULL,
EventType varchar(15) NULL,
LoginName VARCHAR(50),
ServerName varchar(25) NULL,
DatabaseName varchar(25) NULL,
ObjectType varchar(25) NULL,
ObjectName varchar(60) NULL,
UserName varchar(15) NULL,
CommandText varchar(max) NULL
--,Entire_Event_Data XML
)
go
*/
CREATE TRIGGER [ddltrg_Audit_Log] ON DATABASE -- Create Database DDL Trigger
FOR CREATE_TABLE, DROP_TABLE, ALTER_TABLE,
CREATE_INDEX, DROP_INDEX, ALTER_INDEX,
CREATE_VIEW, ALTER_VIEW, DROP_VIEW,
CREATE_SCHEMA, ALTER_SCHEMA, DROP_SCHEMA,
CREATE_FUNCTION, ALTER_FUNCTION, DROP_FUNCTION,
CREATE_PROCEDURE, ALTER_PROCEDURE, DROP_PROCEDURE,
CREATE_TRIGGER, ALTER_TRIGGER, DROP_TRIGGER,
CREATE_USER, ALTER_USER, DROP_USER
/*
CREATE TRIGGER ddltrg_Server_Audit_Log ON ALL SERVER -- Create Database DDL Trigger
FOR
CREATE_DATABASE, ALTER_DATABASE, DROP_DATABASE
*/
AS
--http://www.sql-server-performance.com/articles/audit/ddl_triggers_p1.aspx
--http://searchsqlserver.techtarget.com/tip/0,289483,sid87_gci1346274,00.html for event types
--See http://msdn.microsoft.com/en-us/library/ms189871%28SQL.90%29.aspx for event types
SET NOCOUNT ON
If Object_ID('dba_repo.dbo.DDL_Event_Log') IS NOT NULL
BEGIN
DECLARE @xmlEventData XML
-- Capture the event data that is created
SET @xmlEventData = eventdata()
-- Insert information to a Event_Log table
INSERT INTO dba_repo.dbo.DDL_Event_Log
(
EventTime,
EventType,
LoginName,
ServerName,
DatabaseName,
ObjectType,
ObjectName,
UserName,
CommandText
-- , Entire_Event_Data
)

SELECT REPLACE(CONVERT(VARCHAR(50), @xmlEventData.query('data(/EVENT_INSTANCE/PostTime)')),'T', ' '),
CONVERT(VARCHAR(15), @xmlEventData.query('data(/EVENT_INSTANCE/EventType)')),
CONVERT(VARCHAR(50), @xmlEventData.query('data(/EVENT_INSTANCE/LoginName)')),
CONVERT(VARCHAR(25), @xmlEventData.query('data(/EVENT_INSTANCE/ServerName)')),
CONVERT(VARCHAR(25), @xmlEventData.query('data(/EVENT_INSTANCE/DatabaseName)')),
CONVERT(VARCHAR(25), @xmlEventData.query('data(/EVENT_INSTANCE/ObjectType)')),
CONVERT(VARCHAR(60), @xmlEventData.query('data(/EVENT_INSTANCE/ObjectName)')),
CONVERT(VARCHAR(15), @xmlEventData.query('data(/EVENT_INSTANCE/UserName)')),
CONVERT(VARCHAR(MAX), @xmlEventData.query('data(/EVENT_INSTANCE/TSQLCommand/CommandText)'))
-- , @xmlEventData
END

[Cruft] New DMV in 2008 - SP details

One of the things I've been hoping/waiting/praying for, in SQL 2008, is the ability to see when an SP was last run. In 2000 and 2005 you can do it, so long as it's still in the cache. Which means that things only run sporadically won't occur.

Imagine my happiness:

SELECT * FROM sys.dm_exec_procedure_stats

Extra credit: join to sys.procedures (also new) to get the object.

So, now you can see, since the server was started, what runs. And since your server stays up for several months at a time, you have a good "hit list" of procs that can be scripted out and removed.

I'll update this post when we get a good working version.
(Thanks to Hammer for his help)