Help Center/ Data Admin Service/ User Guide/ RDS for MySQL/ Intelligent O&M (New Version)/ SQL/ SQL Throttling
Updated on 2025-11-24 GMT+08:00
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SQL Throttling

To ensure stability of core services, DAS throttles SQL statements based on specified rules when they cannot be tuned in a timely manner or when resource (for example, CPU) usage reaches 100%.

Usage Notes

  • The kernel version of primary RDS for MySQL instances must be 5.6.50.3, 5.7.31.4, 8.0.25.1, or later.
  • The kernel version of RDS for MySQL read replicas must be 5.6.51.6, 5.7.37.1, 8.0.25.1, or later.
  • Separate concurrency rules can be added for read replica instances of RDS for MySQL of the kernel version 5.7.38-221000 or later (5.6 and 8.0 are not supported).
  • If a SQL statement matches multiple throttling rules, only the most recently added rule is applied.
  • Keywords in a SQL throttling rule are sorted in a specific order, and the system will match them from first to last. For example, if one rule contains the keyword a~and~b, the system only matches xxx a>1 and b>2.
  • If the replication delay is too long, adding or deleting a SQL throttling rule for a read replica instance does not take effect immediately.
  • If you replicate data from an instance to a third-party instance based on binlogs, deleting or adding SQL statement concurrency rules from or to the instance will interrupt the replication process.
  • Each SQL throttling rule can contain a maximum of 128 keywords.
  • Only SELECT, UPDATE, DELETE, and INSERT statements can be throttled.
  • Empty characters before and after each keyword will be ignored, for example, spaces, \n, \r, and \t.
  • Too many keywords or rules may affect performance. Retain only necessary rules.
  • A maximum of 100 SQL throttling rules can be retained.
  • Throttling rules are not applied to SQL statements stored in the query cache.
  • SQL throttling is invalid for:
    • System tables
    • SQL statements not used to query data, such as SELECT SLEEP(xxx)
    • User root in versions including 5.6, 5.7.41.230700 and earlier versions in 5.7, and 8.0.28.230701 and earlier versions in 8.0
    • Stored procedures, triggers, and functions

Procedure

  1. Log in to the console.
  2. Click in the upper left corner and select a region and project.
  3. Click in the upper left corner, and under Databases, click Data Admin Service.
  4. In the navigation pane, choose Intelligent O&M > Instance List.

    Alternatively, on the Overview page, click Go to Intelligent O&M.

  5. In the upper right corner of the Instance List page, search for instances by engine type, instance name, or instance IP.
  6. Locate the target instance and click Details.
  7. Click the SQL tab and then SQL Throttling.
  8. On the displayed page, toggle on Enable SQL Throttling.

    Figure 1 Enabling SQL throttling

  9. In the dialog box at the top of the page, click View Versions.

    Figure 2 Viewing versions

  10. Click Add Rule. In the displayed dialog box, specify SQL Type, Keyword, and Max. Concurrency.

    Figure 3 Add Rule
    • Keyword: You can enter keywords or copy an existing SQL statement to the text box and click Generate Keyword.
      • Keywords generated from an original SQL statement are only for reference.
      • Each SQL throttling rule can contain a maximum of 128 keywords.

      The following explains how a rule matches SQL statements based on keywords:

      For example, if you enter the keywords select~id~name~from~t3~where~age~>~27 (the keywords are separated by a tilde (~)) for a rule, the system will match them from first to last and restrict the execution of any SQL statement that contains these keywords.

    • Max. Concurrency: SQL statements that meet the specified SQL type and keywords and exceed the value of Max. Concurrency will not be executed.

      SQL statements executed before a throttling rule is added will not be counted.

      If you add a SQL throttling rule and set Max. Concurrency to 0, the following concurrent statements will be throttled:

      "select id, name from t3 where age > 27"
"select id, name, age from t3 where age > 27"
"select id, name from t3 where age > 5 and id < 27"

      But the concurrency of the following SQL statement will not be controlled:

      "select name, age from t3 where age > 27"

  11. Confirm the settings and click OK.

    If a SQL throttling rule is no longer needed, click Delete in the Operation column.

Parent topic: SQL