How to find the percentage of row modifications since last statistics update
Introduction
Why Does It Matter?
Find the percentage of row modifications with T-SQL
T-SQL description
Recommendation
Conclusion
Introduction
In the world of databases, keeping things running smoothly is key. Imagine your data as a ship sailing through the vast ocean of information.
But just like real ships, databases need regular checks to ensure they're on the right course. One crucial aspect is understanding how much your data has
changed recently, and that's where the concept of row modifications comes in.
Why Does It Matter?
Understanding these numbers helps us steer our data ship more effectively. Let's say we find a high percentage of modifications since the last update.
That's like discovering a storm brewing ahead. If we ignore it, our queries might slow down, just like navigating through rough waters. But if we update
our statistics regularly, it's like installing better navigation tools to sail through smoothly.
Find the percentage of row modifications with T-SQL
This SQL query retrieves information from the dynamic management views, providing the percentage of row modifications since last statistics update for a given database.
use dbdocs; -- Replace it with your Application database
select
object_schema_name(i.id) object_schema,
tbls.name as table_name,
i.name as index_name,
i.indid,
i.rowmodctr as modified_rows,
i.rowcnt,
convert(decimal(18,8), i.rowmodctr / i.rowcnt) as modified_percent,
stats_date(i.id, i.indid) as last_stats_update
from
sysindexes i
inner join
sysobjects tbls
on i.id = tbls.id
inner join
sysusers schemas
on tbls.uid = schemas.uid
inner join
information_schema.tables tl
on tbls.name = tl.table_name
and schemas.name = tl.table_schema
and tl.table_type = 'BASE TABLE'
where
0 < i.indid
and
tl.table_schema <> 'sys'
and
i.rowmodctr <> 0
and
i.rowcnt <> 0
order by
modified_percent desc;
T-SQL description
Now, let's break down each component and understand its significance
Column | Description
----------------- | ------------------------------------------------------------------
object_schema | Object name.
table_name | Table name.
index_name | Index name.
indid | Index ID.
rows_modified | Number of rows modified.
row_count | Total number of rows.
modified_percent | Percentage of rows modified.
last_stats_update | Date of last statistics update.
Recommendation
If the percentage of modifications is significant, but the statistics haven't been updated recently, the query optimizer may not have accurate information
for generating execution plans.
Schedule regular statistics updates for tables and indexes to ensure the query optimizer has up-to-date information for efficient query execution.
Conclusion
Understanding the percentage of row modifications in your SQL Server database is essential for maintaining optimal query performance. By analyzing this
data and taking appropriate actions, such as index optimization and statistics updates, you can ensure that your database operates efficiently and delivers
the best possible performance for your applications. Stay vigilant, keep monitoring, and be proactive in managing your database to unleash its full potential.
Related content