SQL Server Team-based Development - Red Gate Software

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Chapter 11: SQL Refactoring
Before we even consider refactoring your SQL code, it's worth performing a sanity
check on the existing indexing strategy. Maybe all we need to do is add or remove a
few indexes and not really touch any code. There are two DMOs, sys.dm_db_index_
operational_stats and sys.dm_db_index_usage_stats that can be used to
investigate usage of current indexes, and a set of four sys.dm_db_missing_index_*
DMOs that will report on indexes that that the query optimizer might find useful, but are
missing. Microsoft Books Online is a good reference source for the DMOs, as is the book,
Performance Tuning with SQL Server Dynamic Management Views by Louis Davidson and
Tim Ford (http://tinyurl.com/3x5cc9c).
At the start of any refactoring effort, one of the things I do is run the script shown in
Listing 11-2. It queries a system view and INFORMATION_SCHEMA view, looking for some
of the most common "signs of trouble," including objects with long definitions (over 5,000
chars), cursors, functions on column names and use of SELECT *. We'll examine each of
these "anti-patterns" in more detail a little later.
WITH cteObjectText
AS (
– – get text of objects that have it
– – in the list we're checking the text of
– – CHECK_CONSTRAINT, DEFAULT_CONSTRAINT,
– – SQL_SCALAR_FUNCTION, SQL_STORED_PROCEDURE,
– – SQL_TABLE_VALUED_FUNCTION, SQL_TRIGGER, VIEW
SELECT OBJECT_DEFINITION(object_id) object_text ,
name ,
object_id
FROM sys.objects
WHERE type IN ( 'C', 'D', 'FN', 'P', 'TF', 'TR',
'V' )
),
cteColumnNames
AS (
– – get all distinct column names in the database
SELECT DISTINCT
'(' + COLUMN_NAME AS LeftParen ,
COLUMN_NAME + ')' AS RightParen
FROM INFORMATION_SCHEMA.COLUMNS