MySQL Bugs: #37132: Logging to slow_log table fails with very slow queries

Bug #37132	Logging to slow_log table fails with very slow queries
Submitted:	2 Jun 2008 3:48	Modified:	19 Jun 2019 1:23
Reporter:	Omer Barnir (OCA)	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Logging	Severity:	S3 (Non-critical)
Version:	5.1.25	OS:	Any
Assigned to:	Assigned Account	CPU Architecture:	Any

Description:
While running the 'large_test' observed that the two slowest queries were not logged to the slow log table and the following errors were recorded in the master.err file:
  080601  5:45:55 [ERROR] Failed to write to mysql.slow_log:
  080601  6:19:32 [ERROR] Failed to write to mysql.slow_log:
The queries were logged correctly to the slow log file:
# Time: 080601  5:45:55
# User@Host: root[root] @ localhost []
# Query_time: 901.996373  Lock_time: 0.000085 Rows_sent: 0  
  Rows_examined: 2147483648
SET timestamp=1212288355;
insert into t1 select * from t1;
# Time: 080601  6:19:32
# User@Host: root[root] @ localhost []
# Query_time: 2017.081880  Lock_time: 0.000102 Rows_sent: 0  
  Rows_examined: 4294967294
SET timestamp=1212290372;
insert into t1 select * from t1 limit 2147483647;

How to repeat:
Run:
mysql-test-run.pl --suite=large_tests --big-test --suite-timeout=6360 --testcase-timeout=795
Note: the test runs for around 5 hours and requires around 60GB of disk before the problems shows

Suggested fix:
Log the entries in the slow-log table

You may fail to write into the log table due to many reasons: out of memory, out of disk space, etc.
We should change the code to print the error message into the error log, then re-run the test.
Medium effort since the test case is so big.

We see the same issue in MySQL 5.6.  Will this bug get fixed?

Posted by developer:
 
Fixed in 8.0.17.

Logging to the mysql.slow_log system table could fail when values
were to large for table columns. Now logging proceeds on a
best-effort basis, writing what information can be provided.
Otherwise, the row is discarded and a message is written to the error
log.