Viewing and Downloading Slow Query Logs

Scenarios

Slow query logs record statements that exceed the long_query_time value (1 second by default). You can view log details and statistics to identify statements that are executing slowly and optimize the statements. You can also download slow query logs for service analysis.

Slow query logs generated within the last month can be viewed.

Parameter Description

Table 1 Parameters related to slow queries

Parameter	Description
long_query_time	Specifies how many microseconds a SQL query has to take to be defined as a slow query log. The default value is 1s. When the execution time of an SQL statement exceeds the value of this parameter, the SQL statement is recorded in slow query logs. The recommended value is 1s. Note: The lock wait time is not calculated into the query time. Modifying long_query_time takes effect globally. After the modification, the new value is applied to new connections. The existing connections still use the old value.
log_queries_not_using_indexes	Specifies whether to record the slow query without indexes. The default value is OFF.
log_throttle_queries_not_using_indexes	Limits the number of SQL statements without indexes per minute that can be written to the slow query log. The default value is 0.

Showing Original Logs

NOTE:

Original logs will be automatically deleted 30 days later. If the instance is deleted, its logs are also deleted.

1. Click in the upper left corner and select a region.
2. Click in the upper left corner of the page and choose Databases > Relational Database Service.
3. On the Instances page, click the DB instance name.
4. In the navigation pane on the left, choose Logs. On the Slow Query Logs page, click Log Details and then click on the right of Show Original Logs.
   Figure 1 Enabling Show Original Logs
   

5. In the displayed dialog box, click Yes to enable the display of original slow query logs.

Viewing Log Details

1. Click in the upper left corner and select a region.
2. Click in the upper left corner of the page and choose Databases > Relational Database Service.
3. On the Instances page, click the DB instance name.
4. In the navigation pane on the left, choose Logs. On the Slow Query Logs page, click Log Details to view details about slow query logs.
   Figure 2 Slow query log details
   
   NOTE:

   • You can view the slow query log records of a specified execution statement type or a specific time period.
   • Only SELECT statements return the number of result rows. The number of result rows for the INSERT, UPDATE, DELETE, and CREATE statements is 0 by default.
   • You can view slow query logs of a specified database name (which cannot contain any special characters). The database name supports only exact search.
   • Slow query logs only record executed statements whose execution duration exceeds the threshold.
   • The long_query_time parameter determines when a slow query log is recorded. However, changes to this parameter do not affect already recorded logs. If long_query_time is changed from 1s to 0.1s, RDS starts recording statements that meet the new threshold and still displays the previously recorded logs that do not meet the new threshold. For example, a 1.5s SQL statement that was recorded when the threshold was 1s will not be deleted now that the new threshold is 2s.
   • A maximum of 2,000 slow log records can be displayed. To view more slow log records, contact customer service.
   • If the length of a single line of an SQL statement exceeds 10 KB or the total number of lines exceeds 200, the SQL statement will be truncated. When you view slow query log details, the SQL statement may be incomplete after special processing and is for reference only.

Viewing Statistics

1. Click in the upper left corner and select a region.
2. Click in the upper left corner of the page and choose Databases > Relational Database Service.
3. On the Instances page, click the DB instance name.
4. In the navigation pane on the left, choose Logs. On the Slow Query Logs page, click Statistics to view details.
   Figure 3 Statistics
   
   NOTE:

   • On the Statistics page, only one of the SQL statements of the same type is displayed as an example. For example, if two select sleep(N) statements, select sleep(1) and select sleep(2), are executed in sequence, only select sleep(1) will be displayed.
   • However, if Show Original Logs is enabled, all of the slow SQL statements are displayed. For example, if select sleep(1) and select sleep(2) are executed in sequence, both of them will be displayed.
   • No. and Ratio of SQL Executions indicates the ratio of the slow executions to the total executions of the SQL statement.
   • On the Statistics page, only the latest 5,000 slow SQL statements within a specified period are analyzed.
   • You can filter slow log statistics by database name (which cannot contain any special characters), statement type, or time period. The database name supports only exact search.
   • If any database name in the slow log statistics contains special characters such as < > ', the special characters will be escaped.

Downloading a Slow Query Log

You can download a log file that is not larger than 40 MB directly from the console. The time range is calculated from the time you download the file back to the time when the accumulated file size reaches 40 MB.

To download a log file larger than 40 MB, use OBS Browser+.

Enabling Slow Log Reporting to LTS

1. Click in the upper left corner and select a region.
2. Click in the upper left corner of the page and choose Databases > Relational Database Service.
3. On the Instances page, click the DB instance name.
4. In the navigation pane, click Logs. On the Slow Query Logs page, click Log Details.
5. Click next to Report Slow Logs to LTS.
6. Select an LTS log group and log stream and click OK.
   Figure 10 Enabling slow log reporting to LTS