MariaDB - Utf8mb4 Collation Specifier In Select Query Results In Long Query Time

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Introduction

MariaDB is a popular open-source relational database management system. It is widely used in various applications, including ownCloud, a popular cloud storage solution. However, in some cases, MariaDB can experience long query times, especially when using the utf8mb4 collation specifier in select queries. In this article, we will explore the issue of long query times in MariaDB when using the utf8mb4 collation specifier and provide possible solutions.

Background

ownCloud is a cloud storage solution that uses MariaDB as its database management system. The database is configured to use the utf8mb4 charset and utf8mb4_bin collation. However, when running the occ system:cron command, the query time can be very long, sometimes taking up to 40 seconds. This can cause significant performance issues and impact the overall user experience.

Steps to Reproduce

To reproduce the issue, follow these steps:

  1. Use an ownCloud server that has been updated from time to time and uses file versions and trashbin.
  2. Upgrade to using the utf8mb4 charset and utf8mb4_bin collation.
  3. Observe the long run and heavy CPU load during the occ system:cron command.

Expected Behavior

The expected behavior is that the occ system:cron command should run lightning-fast.

Actual Behavior

The actual behavior is that the occ system:cron command takes a very long time to run, sometimes up to 40 seconds, and causes heavy CPU load.

Analysis

To analyze the issue, we need to understand how MariaDB handles collations and how it affects query performance. In MariaDB, collations are used to determine the sorting and comparison rules for character data. The utf8mb4 collation specifier is used to specify the character set and collation for a query.

When using the utf8mb4 collation specifier in a select query, MariaDB may experience long query times due to the following reasons:

  • Collation mismatch: If the collation specified in the query does not match the collation of the column, MariaDB may need to perform additional operations to convert the data, leading to slower query performance.
  • Index usage: If the index is not used due to collation mismatch, MariaDB may need to perform a full table scan, leading to slower query performance.

Experimentation

To experiment with the issue, we can try the following:

  • Add index on the name column: Adding an index on the name column can improve query performance by allowing MariaDB to use the index instead of performing a full table scan.
  • Specify collation in the query: Specifying the collation in the query can help MariaDB determine the correct collation to use, leading to faster query performance.
  • Use the utf8mb4_bin collation: Using the utf8mb4_bin collation can help MariaDB determine the correct collation to use, leading to faster query performance.

Results

The results of the experimentation are as follows:

  • Adding index on the name column: Adding an index on the name column can improve query performance by allowing MariaDB to use the index instead of performing a full table scan.
  • Specifying collation in the query: Specifying the collation in the query can help MariaDB determine the correct collation to use, leading to faster query performance.
  • Using the utf8mb4_bin collation: Using the utf8mb4_bin collation can help MariaDB determine the correct collation to use, leading to faster query performance.

Conclusion

In conclusion, the issue of long query times in MariaDB when using the utf8mb4 collation specifier can be caused by collation mismatch, index usage, and other factors. By adding an index on the name column, specifying the collation in the query, and using the utf8mb4_bin collation, we can improve query performance and reduce the time it takes to run the occ system:cron command.

Recommendations

Based on the analysis and experimentation, we recommend the following:

  • Add index on the name column: Adding an index on the name column can improve query performance by allowing MariaDB to use the index instead of performing a full table scan.
  • Specify collation in the query: Specifying the collation in the query can help MariaDB determine the correct collation to use, leading to faster query performance.
  • Use the utf8mb4_bin collation: Using the utf8mb4_bin collation can help MariaDB determine the correct collation to use, leading to faster query performance.

Server Configuration

The server configuration is as follows:

  • Operating system: Linux
  • Web server: Apache (docker image, 10.13.4)
  • Database: MariaDB (10.3.10-MariaDB-log)
  • PHP version: 7.4.3 (docker image, 10.13.4)
  • ownCloud version: 10.13.4 (docker image, 10.13.4)

Conclusion

Q&A

Q: What is the issue with MariaDB and the utf8mb4 collation specifier? A: The issue is that MariaDB can experience long query times when using the utf8mb4 collation specifier in select queries.

Q: What are the possible causes of the issue? A: The possible causes of the issue are:

  • Collation mismatch: If the collation specified in the query does not match the collation of the column, MariaDB may need to perform additional operations to convert the data, leading to slower query performance.
  • Index usage: If the index is not used due to collation mismatch, MariaDB may need to perform a full table scan, leading to slower query performance.

Q: How can I improve query performance in MariaDB? A: To improve query performance in MariaDB, you can try the following:

  • Add index on the name column: Adding an index on the name column can improve query performance by allowing MariaDB to use the index instead of performing a full table scan.
  • Specify collation in the query: Specifying the collation in the query can help MariaDB determine the correct collation to use, leading to faster query performance.
  • Use the utf8mb4_bin collation: Using the utf8mb4_bin collation can help MariaDB determine the correct collation to use, leading to faster query performance.

Q: What is the difference between utf8mb4 and utf8mb4_bin collations? A: The utf8mb4 collation is a case-insensitive collation, while the utf8mb4_bin collation is a case-sensitive collation. The utf8mb4_bin collation is used for binary data, such as images and videos.

Q: How can I determine the correct collation to use in my query? A: To determine the correct collation to use in your query, you can use the SHOW COLLATION statement to list all available collations in your database. You can then specify the collation in your query using the COLLATE keyword.

Q: What are the benefits of using the utf8mb4_bin collation? A: The benefits of using the utf8mb4_bin collation are:

  • Faster query performance: Using the utf8mb4_bin collation can improve query performance by allowing MariaDB to use the index instead of performing a full table scan.
  • Improved data integrity: Using the utf8mb4_bin collation can help ensure data integrity by preventing data corruption due to collation mismatch.

Q: Can I use the utf8mb4_bin collation with other collations? A: Yes, you can use the utf8mb4_bin collation with other collations. However, you should be aware that using multiple collations can lead to performance issues and data corruption.

Q: How can I troubleshoot issues with MariaDB and the utf8mb4 collation specifier? A: To troubleshoot issues with MariaDB and the utf8mb4ation specifier, you can try the following:

  • Check the query plan: Use the EXPLAIN statement to check the query plan and identify any performance issues.
  • Check the collation: Use the SHOW COLLATION statement to check the collation of the column and the query.
  • Check the index: Use the SHOW INDEX statement to check the index on the column and the query.

Q: Can I use MariaDB with other databases? A: Yes, you can use MariaDB with other databases. However, you should be aware that using multiple databases can lead to performance issues and data corruption.

Q: How can I upgrade MariaDB to the latest version? A: To upgrade MariaDB to the latest version, you can follow these steps:

  • Backup your data: Backup your data to prevent data loss.
  • Download the latest version: Download the latest version of MariaDB from the official website.
  • Install the latest version: Install the latest version of MariaDB using the installation instructions.
  • Upgrade your database: Upgrade your database to the latest version using the upgrade instructions.

Q: Can I use MariaDB with other programming languages? A: Yes, you can use MariaDB with other programming languages. However, you should be aware that using multiple programming languages can lead to performance issues and data corruption.

Q: How can I troubleshoot issues with MariaDB and other programming languages? A: To troubleshoot issues with MariaDB and other programming languages, you can try the following:

  • Check the query plan: Use the EXPLAIN statement to check the query plan and identify any performance issues.
  • Check the collation: Use the SHOW COLLATION statement to check the collation of the column and the query.
  • Check the index: Use the SHOW INDEX statement to check the index on the column and the query.

Conclusion

In conclusion, the issue of long query times in MariaDB when using the utf8mb4 collation specifier can be caused by collation mismatch, index usage, and other factors. By adding an index on the name column, specifying the collation in the query, and using the utf8mb4_bin collation, we can improve query performance and reduce the time it takes to run the occ system:cron command.