RuntimeStats for cluster_slow_query

[dveeden]

In #20200 stats were added for the information_schema.slow_query table. However there is nothing for the similar information_schema.cluster_slow_query table.

Example:

mysql-8.0.11-TiDB-v8.4.0-alpha-364-gd5796776c1-dirty> EXPLAIN ANALYZE SELECT * FROM information_schema.slow_query LIMIT 1;
+-----------------------+----------+---------+------+------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------+-------------------------------------------------+---------+------+
| id                    | estRows  | actRows | task | access object    | execution info                                                                                                                                          | operator info                                   | memory  | disk |
+-----------------------+----------+---------+------+------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------+-------------------------------------------------+---------+------+
| Limit_7               | 1.00     | 1       | root |                  | time:1.94ms, loops:2, RU:0.000000                                                                                                                       | offset:0, count:1                               | N/A     | N/A  |
| └─MemTableScan_10     | 10000.00 | 64      | root | table:SLOW_QUERY | time:1.93ms, loops:1, initialize: 25.8µs, read_file: 912µs, parse_log: {time:1.78ms, concurrency:15}, total_file: 1, read_file: 1, read_size: 4.05 MB   | only search in the current 'tidb-slow.log' file | 1.25 MB | N/A  |
+-----------------------+----------+---------+------+------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------+-------------------------------------------------+---------+------+
2 rows in set (0.00 sec)

mysql-8.0.11-TiDB-v8.4.0-alpha-364-gd5796776c1-dirty> EXPLAIN ANALYZE SELECT * FROM information_schema.cluster_slow_query LIMIT 1;
+---------------------------+---------+---------+-----------+--------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------------+---------+------+
| id                        | estRows | actRows | task      | access object            | execution info                                                                                                                                                            | operator info     | memory  | disk |
+---------------------------+---------+---------+-----------+--------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------------+---------+------+
| Limit_7                   | 1.00    | 1       | root      |                          | time:2.89ms, loops:2, RU:0.515024                                                                                                                                         | offset:0, count:1 | N/A     | N/A  |
| └─TableReader_12          | 1.00    | 1       | root      |                          | time:2.89ms, loops:1, cop_task: {num: 1, max: 2.8ms, proc_keys: 0, copr_cache_hit_ratio: 0.00, max_distsql_concurrency: 1}, rpc_info:{Cop:{num_rpc:1, total_time:2.75ms}} | data:Limit_11     | 2.70 KB | N/A  |
|   └─Limit_11              | 1.00    | 0       | cop[tidb] |                          |                                                                                                                                                                           | offset:0, count:1 | N/A     | N/A  |
|     └─MemTableScan_10     | 1.00    | 0       | cop[tidb] | table:CLUSTER_SLOW_QUERY |                                                                                                                                                                           |                   | N/A     | N/A  |
+---------------------------+---------+---------+-----------+--------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------------+---------+------+
4 rows in set (0.00 sec)

Note the initialize: 25.8µs, read_file: 912µs, parse_log: {time:1.78ms, concurrency:15}, total_file: 1, read_file: 1, read_size: 4.05 MB

This is generated here:

tidb/pkg/executor/slow_query.go

Line 1115 in 2e51209

return fmt.Sprintf("initialize: %s, read_file: %s, parse_log: {time:%s, concurrency:%v}, total_file: %v, read_file: %v, read_size: %s",

For the cluster_slow_query table you can see that there are no stats:

tidb/pkg/executor/memtable_reader.go

Lines 592 to 594 in 2e51209

	func (*clusterLogRetriever) getRuntimeStats() execdetails.RuntimeStats {
	return nil
	}

What the stats could show:

• Number of files read
• Number of nodes involved
• CPU usage
• Time
• Memory usage
• Read bytes
• Read number of entries
• Concurrency

Most of these could be per-node, in total or both.

[dveeden]

This could help with cases like this: #54522