Problem Queries are Killing Your Database Performance

Author: Robert Agar

Tuning database performance is a complicated task that can be a thorn in the side of the database team. There are many interconnected components and environmental aspects that come under consideration when attempting to optimize the performance of your database systems. A DBA can be hard-pressed to determine where to begin their optimization efforts.

An initial investigation may concentrate on the network and hardware on which the database is running. These inquiries may uncover issues that can be easily identified and addressed. It may be a simple matter of adding some disk space or upgrading memory on the database’s server. You might be able to move the database to a less-used network segment to improve the response time when satisfying user requests. Maybe there are conflicting applications or processes on the same server that are impacting the availability of resources to power the database.

Hopefully, some of these steps allow you to achieve the performance gains that you seek. But what if they don’t? Numerous attempts at modifying system parameters and juggling components can leave you right where you started. Your database is still underperforming and pressure is building to resolve the problem. It’s time to dig into the programming logic that provides functionality to the database’s users. Don’t be frightened, but you need to go under the hood and take a look at your SQL queries and optimize the ones that are negatively impacting the system.

Methods of Improving SQL Query Performance

Multiple factors can influence the speed at which SQL queries are executed. This also means that there are a variety of ways to address SQL queries that are causing deficient database performance. If you are responsible for MySQL databases, here are some methods that may improve the execution speed of your SQL queries.

  • Use the MySQL full-text search facility. Searching your database with wildcards can lead to significantly slower response time. Here’s some sample code that illustrates adding this feature to a query. Making this type of change can drastically speed up your queries by narrowing the query and eliminating unnecessary scanning for data.

mysql>Alter table students ADD FULLTEXT (first_name, last_name);

mysql>Select * from students where match(first_name, last_name) AGAINST (‘Ade’);

  • Fine-tune your Like statements. You should stay away from Like expressions that contain leading wildcards. A leading wildcard in a query inhibits MySQL from utilizing indexes and forces it to perform a full table scan. This is probably not the most efficient way to query your database, and eliminating the wildcard will lead to improved response time.

  • Another way to improve Like statement performance is by using the Union clause. Using a Union rather than the ‘or’ operator can help reduce the potential that the MySQL optimizer will retrieve records via a full table scan.

  • Indexing columns where it is appropriate can lead to performance gains. An index can increase the speed at which MySQL server returns query results. Adding indexes to columns that employ ‘where’ and ‘group by’ clauses can help you achieve better query performance.

  • Care must be taken when adding indexes to your database tables. Incorrect indexing can impact the overall well-being of your system and lead to degraded performance. Before haphazardly adding indexes to your database tables you should perform two checks. These steps are to verify the database’s existing structure and to confirm the size of the table. This information can help you determine if the index you intend to add is already present in some form and help you estimate the time impact of adding the index. 

Finding the Right Queries to Optimize

Having techniques that allow you to optimize a database’s SQL queries certainly presents a way to improve the system’s performance. However, you may face some difficulty in establishing which queries deserve your attention. SQL Diagnostic Manager for MySQL furnishes a DBA with a comprehensive performance monitor that can help identify the SQL queries that will provide the greatest benefits by being optimized.

SQL Diagnostic Manager for MySQL provides a host of features that will help you optimize the performance of your MySQL and MariaDB systems. It supplies real-time details of slow or locked queries and allows you to kill them if necessary. You can easily identify the top 10 queries based on execution time, which gives you a great starting point for query optimization. The tool works on databases located on-premises as well as those residing in the cloud. It’s an excellent way to find and address the problem SQL queries that may be dragging down your database performance.

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