This topic describes the limits of Scheduled SQL.
Special tasks
Features in Simple Log Service (SLS), such as Trace and Cloud Lens for SLB, depend on Scheduled SQL. To ensure that these features run correctly, Scheduled SQL restricts changes to these tasks. These tasks cannot be updated, copied, or deleted from the Scheduled SQL task management interface. To perform these operations, you must use the interfaces of the respective features.
Query and analysis
Scheduled SQL supports only the Dedicated SQL engine.
Limit | Description |
Concurrency | A single project supports a maximum of 100 concurrent analysis operations. For example, 100 users can run analysis operations at the same time on different Logstores in the same project. |
Data volume | A single analysis can scan a maximum of 200 billion rows of data. |
Data activation process | The analysis feature works only on data that is written after you enable the statistics feature. To analyze historical data, reindex the data. For more information, see Reindex. |
Return values |
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Field value size | The default size of a single field value is 2,048 bytes (2 KB), and the maximum size is 16,384 bytes (16 KB). Values that exceed the maximum size are not included in the analysis. You can change the maximum length of a field value to a value from 64 bytes to 16,384 bytes when you configure an index. For more information, see Create an index. |
Timeout | The maximum timeout for an analysis operation is 10 minutes. |
Number of bits for Double-type field values | A Double-type field value has a precision of up to 52 bits. A loss of precision occurs if a floating-point number is encoded with more than 52 bits. |
Fuzzy query | When you run a fuzzy query, SLS finds a maximum of 100 matching terms and returns all logs that contain these terms and meet the query conditions. |
Inaccurate results | Inaccurate results do not cause an error. They are recorded in the instance status and task execution records. You must manually enable task execution records. |
Data latency | Data latency can cause data to be missed during queries. For example, if data for a specific time point arrives after the corresponding scheduled instance finishes running, the data is not processed by the next scheduled instance. For more information, see How to ensure the accuracy of SQL analysis. |
Time window | The maximum time window for a single query is 24 hours, and the minimum is 1 minute. |
Metastore association | Not supported. |
LIMIT clause | In Scheduled SQL, only the |
Data writes
Limit | Description |
Destination Logstore write threshold | If the write threshold is exceeded when data is written, the Scheduled SQL task retries for more than 10 minutes. If the task still fails after the retry time expires, an error message is returned. For more information, see Data reads and writes. |
Cross-region transfer | When you transfer data across regions within mainland China, the network is relatively stable, but high latency may occur. The latency varies based on the region. The stability of international networks is not guaranteed. |
Task execution
Limit | Description |
Timeout | The maximum timeout is 1800 seconds. If a task execution exceeds this limit, it is considered failed. Add an alerting monitoring job to promptly detect issues and retry failed instances. For more information, see Set alerts for a Scheduled SQL task and Retry a Scheduled SQL task instance. |
Number of retries | The maximum number of retries is 100. If this limit is exceeded, the task execution is considered failed. |
Delayed execution | The maximum delayed execution time is 120 seconds. For examples of delayed execution scenarios, see Scheduling and execution scenarios. |
Historical execution records | The historical execution records of a single task are saved for a maximum of 5 days. Add an alerting monitoring job to promptly detect issues and retry failed instances. For more information, see Set alerts for a Scheduled SQL task and Retry a Scheduled SQL task instance. |