Percona Server with XtraDB

THREAD_STATISTICS is always empty

Reported by Swany on 2011-03-02
10
This bug affects 2 people
Affects Status Importance Assigned to Milestone
Percona Server
Low
Unassigned
5.1
Low
Unassigned
5.5
Low
Unassigned

Bug Description

Reproducible on both 5.1 and 5.5.

mysql> select @@userstat;
+------------+
| @@userstat |
+------------+
| 1 |
+------------+
1 row in set (0.00 sec)

mysql> show thread_statistics;
Empty set (0.00 sec)

mysql> select * from information_schema.thread_statistics;
Empty set (0.01 sec)

Stewart Smith (stewart) wrote :

should be a rather simple test case at least.

Changed in percona-server:
assignee: nobody → Valentine Gostev (core-longbow)
importance: Undecided → Medium
Stewart Smith (stewart) wrote :

mysql> select * from information_schema.thread_statistics;
Empty set (0.00 sec)

mysql> use information_schema;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
mysql> select * from thread_statistics;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'thread_statistics' at line 1
mysql> select * from `thread_statistics`;
Empty set (0.00 sec)

mysql>

Changed in percona-server:
assignee: Valentine Gostev (longbow) → nobody
status: New → Triaged
importance: Medium → Low

We have a report that 5.1 fails in the same way.

Alexey Kopytov (akopytov) wrote :

There are 2 different issues:

1. THREAD_STATISTICS is a reserved word in 5.5. This is bug #997036.
2. THREAD_STATISTICS is always empty in both 5.1 and 5.5.

This report was originally about issue #1, so technically it's a duplicate of bug #997036 or the other way around. But since there's already some confusion on what this bug is about, let's keep it as a report about issue #2, and bug #997036 as a report about issue #1.

Changing summary and report accordingly.

summary: - THREAD_STATISTICS is not accessible
+ THREAD_STATISTICS is always empty
description: updated
Alexey Kopytov (akopytov) wrote :

And the reason for issue #2, i.e. thread_statistics being an empty table, is that to enable thread statistics collection, setting userstat to ON is insufficient, one also has to set the thread_statistics variable to ON (5.5 also requires quoting until bug #997036 is fixed):

mysql> select @@userstat;
+------------+
| @@userstat |
+------------+
| 1 |
+------------+
1 row in set (0.00 sec)

mysql> select * from information_schema.thread_statistics;
Empty set (0.00 sec)

mysql> set global `thread_statistics`=on;
Query OK, 0 rows affected (0.01 sec)

mysql> select * from information_schema.thread_statistics\G
*************************** 1. row ***************************
             THREAD_ID: 1
     TOTAL_CONNECTIONS: 1
CONCURRENT_CONNECTIONS: 0
        CONNECTED_TIME: 2
             BUSY_TIME: 0
              CPU_TIME: 0
        BYTES_RECEIVED: 55
            BYTES_SENT: 0
  BINLOG_BYTES_WRITTEN: 0
          ROWS_FETCHED: 1
          ROWS_UPDATED: 0
       TABLE_ROWS_READ: 0
       SELECT_COMMANDS: 1
       UPDATE_COMMANDS: 0
        OTHER_COMMANDS: 0
   COMMIT_TRANSACTIONS: 0
 ROLLBACK_TRANSACTIONS: 0
    DENIED_CONNECTIONS: 0
      LOST_CONNECTIONS: 0
         ACCESS_DENIED: 0
         EMPTY_QUERIES: 0
1 row in set (0.00 sec)

Alexey Kopytov (akopytov) wrote :

I see no reasons for having a separate system variable to control thread_statistics. I think the fix for this bug would be to keep the variable for compatibility, but make thread stats enabled when userstat is ON.

tags: added: userstat
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