Prioritize Missing Index Recommendations 2 (2005)
This is an enhanced version of my previous script: Prioritize Missing Index Recommendations (2005).
To aid in evaluation of whether the recommended index is reasonable, I have added :
1. counts for key columns and the total columns of the recommended index
2. the length/bytes for both key and all columns Note this is 'per row', not what the space used would be once actually created
I have also removed the threshold/min row construct, so all recommended indexes will appear.
-- ---------------------------------------------------------------------------------------------------
-- Author: Michael Smith, Minneapolis, MN
-- Date: 2007-08-17
--
-- Purpose: To report indexes proposed by the database engine that have highest probable user impact.
--
-- Gives counts of columns, plus the bytes of columns (key columns and total) to assist in determining
-- if recommended index is a reasonable index to implement.
-- ---------------------------------------------------------------------------------------------------
SET ANSI_NULLS ON;
SET ANSI_PADDING ON;
SET ANSI_WARNINGS ON;
SET ARITHABORT ON;
SET CONCAT_NULL_YIELDS_NULL ON;
SET NUMERIC_ROUNDABORT OFF;
SET QUOTED_IDENTIFIER ON;
SET NOCOUNT ON;
GO
WITH missing_index_impact AS (
SELECT
dm_db_missing_index_groups.index_handle,
SUM(
(dm_db_missing_index_group_stats.avg_total_user_cost * dm_db_missing_index_group_stats.avg_user_impact *
(dm_db_missing_index_group_stats.user_seeks + dm_db_missing_index_group_stats.user_scans))
) AS "total_impact",
(100.00 *
SUM(dm_db_missing_index_group_stats.avg_total_user_cost * dm_db_missing_index_group_stats.avg_user_impact *
(dm_db_missing_index_group_stats.user_seeks + dm_db_missing_index_group_stats.user_scans)) /
SUM(SUM(dm_db_missing_index_group_stats.avg_total_user_cost *
dm_db_missing_index_group_stats.avg_user_impact *
(dm_db_missing_index_group_stats.user_seeks + dm_db_missing_index_group_stats.user_scans))) OVER()
) AS "percent_impact",
ROW_NUMBER() OVER(ORDER BY SUM(avg_total_user_cost * avg_user_impact * (user_seeks + user_scans)) DESC ) AS rn
FROM sys.dm_db_missing_index_groups AS dm_db_missing_index_groups
JOIN sys.dm_db_missing_index_group_stats AS dm_db_missing_index_group_stats
ON dm_db_missing_index_groups.index_group_handle = dm_db_missing_index_group_stats.group_handle
GROUP
BY dm_db_missing_index_groups.index_handle),
agg_missing_index_impact AS (
SELECT missing_index_impact_1.index_handle,
missing_index_impact_1.total_impact,
SUM(missing_index_impact_2.total_impact) AS running_total_impact,
missing_index_impact_1.percent_impact,
SUM(missing_index_impact_2.percent_impact) AS running_total_percent,
missing_index_impact_1.rn
FROM missing_index_impact AS missing_index_impact_1
JOIN missing_index_impact AS missing_index_impact_2
ON missing_index_impact_1.rn <= missing_index_impact_2.rn
GROUP
BY missing_index_impact_1.index_handle, missing_index_impact_1.total_impact,
missing_index_impact_1.percent_impact, missing_index_impact_1.rn
),
missing_index_details AS (
SELECT dm_db_missing_index_details."object_id",
dm_db_missing_index_details.index_handle,
dm_db_missing_index_details."statement",
dm_db_missing_index_details.equality_columns,
dm_db_missing_index_details.inequality_columns,
dm_db_missing_index_details.included_columns
FROM sys.dm_db_missing_index_details AS dm_db_missing_index_details
)
SELECT agg_missing_index_impact.rn,
missing_index_details."statement",
agg_missing_index_impact.running_total_impact,
agg_missing_index_impact.total_impact,
agg_missing_index_impact.running_total_percent,
agg_missing_index_impact.percent_impact,
missing_index_details.equality_columns,
missing_index_details.inequality_columns,
missing_index_details.included_columns,
"key".index_key_column_count,
"key".index_key_column_bytes,
"all".index_all_column_count,
"all".index_all_column_bytes
FROM agg_missing_index_impact AS agg_missing_index_impact
JOIN missing_index_details AS missing_index_details
ON agg_missing_index_impact.index_handle = missing_index_details.index_handle
JOIN (
SELECT missing_index_details1.index_handle,
COUNT(*) AS index_key_column_count,
SUM(COL_LENGTH(missing_index_details1."statement", dm_db_missing_index_columns1.column_name )) AS index_key_column_bytes
FROM missing_index_details AS missing_index_details1
CROSS
APPLY sys.dm_db_missing_index_columns (missing_index_details1.index_handle) AS dm_db_missing_index_columns1
WHERE dm_db_missing_index_columns1.column_usage = 'EQUALITY'
OR dm_db_missing_index_columns1.column_usage = 'INEQUALITY'
GROUP
BY missing_index_details1.index_handle
) AS "key"
ON missing_index_details.index_handle = "key".index_handle
JOIN (
SELECT missing_index_details2.index_handle,
COUNT(*) AS index_all_column_count,
SUM(COL_LENGTH(missing_index_details2."statement", dm_db_missing_index_columns2.column_name )) AS index_all_column_bytes
FROM missing_index_details AS missing_index_details2
CROSS
APPLY sys.dm_db_missing_index_columns (missing_index_details2.index_handle) AS dm_db_missing_index_columns2
GROUP
BY missing_index_details2.index_handle
) AS "all"
ON missing_index_details.index_handle = "all".index_handle
ORDER
BY agg_missing_index_impact.rn ASC;
