The MySQL SYS Schema

The MySQL SYS Schema
Mark Leith
Senior Software Development Manager
MySQL Enterprise Tools, Oracle
Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

Safe Harbor Statement
The following is intended to outline our general product direction. It is intended
for information purposes only, and may not be incorporated into any contract. It
is not a commitment to deliver any material, code, or functionality, and should
not be relied upon in making purchasing decisions. The development, release,
and timing of any features or functionality described for Oracle’s products
remains at the sole discretion of Oracle.

Program Agenda
Introduction to the MySQL sys schema
Installation
Summary Views
Procedures and Functions
1
2
3
4

Introduction to the MySQL sys schema
• Originally called “ps_helper”
• A collection of views, procedures and functions, designed to help
DBA, Developer, and Ops teams
• Implements many of the common day to day DBA and Developer
debugging and tuning use cases

Why the sys schema?
• Performance Schema exposes a huge amount of data, that can be
sliced and diced in many ways
• Many of its tables can implement many different use cases when
looking at the raw data
• The sys schema layers on top the (sometimes complex) queries in
to a packaged set of easy to use views
• The sys schema also layers on a number of functions and
procedures that help format, and record the raw data

Installation from the command line
• $ git clone https://github.com/MarkLeith/mysql-sys.git /tmp/sys
• $ cd /tmp/sys
• $ mysql -u user -p < sys_<version>.sql
!
!
<version> can be 56 or 57, for 5.6 and 5.7 respectively

Installation from MySQL Workbench 6.1+

!
!
select * from sys.version;!
+-------------+---------------+!
| sys_version | mysql_version |!
+-------------+---------------+!
| 1.1.0 | 5.6.17 |!
+-------------+---------------+
11
Checking sys is loaded
select *!
from sys.schema_object_overview!
where db = 'sys';!
+-----+-------------+-------+!
| db | object_type | count |!
+-----+-------------+-------+!
| sys | VIEW | 78 |!
| sys | PROCEDURE | 22 |!
| sys | FUNCTION | 11 |!
+-----+-------------+-------+

MySQL sys views
• Reference set of views solving various administrator use cases
• Simple views, create/copy your own, sys is not “locked down”
• Build upon both performance_schema and INFORMATION_SCHEMA
• Both formatted and raw views are available
• All raw views are prefixed with x$
• Raw views are there for tools to poll
• Formatted views are for humans and the command line

!
• High level user/host overviews
• Breakdowns by:
• IO usage
• Stages
• Statement details
!
• Following show users only
14
User / Host Summary Views
user_summary
user_summary_by_file_io
user_summary_by_file_io_type
user_summary_by_stages
user_summary_by_statement_latency
user_summary_by_statement_type
host_summary
host_summary_by_file_io
host_summary_by_file_io_type
host_summary_by_stages
host_summary_by_statement_latency
host_summary_by_statement_type

user_summary view
mysql> select * from user_summaryG!
*************************** 1. row ***************************!
user: mark!
statements: 3072!
statement_latency: 1.77 s!
statement_avg_latency: 575.29 us!
table_scans: 7!
file_ios: 20043!
file_io_latency: 346.79 ms!
current_connections: 1!
total_connections: 1!
unique_hosts: 1!
current_memory: 515.81 KiB!
total_memory_allocated: 30.69 MiB
MySQL 5.7.4+

user_summary_by_file_io_type view
mysql> select * from user_summary_by_file_io_type;!
+------+--------------------------------------+---------+-------------+-------------+!
| user | event_name | total | latency | max_latency |!
+------+--------------------------------------+---------+-------------+-------------+!
| mark | wait/io/file/myisam/dfile | 19540 | 215.20 ms | 120.79 ms |!
| mark | wait/io/file/myisam/kfile | 501 | 131.58 ms | 57.74 ms |!
| mark | wait/io/file/sql/dbopt | 2 | 17.29 us | 9.17 us |!
| root | wait/io/file/innodb/innodb_log_file | 2079432 | 00:28:27.62 | 1.30 s |!
| root | wait/io/file/myisam/kfile | 5195927 | 00:17:07.33 | 1.17 s |!
| root | wait/io/file/myisam/dfile | 1533813 | 00:07:27.59 | 1.18 s |!
| root | wait/io/file/sql/binlog | 3517008 | 00:03:07.34 | 1.42 s |!
| root | wait/io/file/innodb/innodb_data_file | 20720 | 00:02:37.81 | 492.23 ms |!
| root | wait/io/file/sql/FRM | 41412 | 3.17 s | 80.43 ms |!
| root | wait/io/file/sql/dbopt | 110993 | 1.23 s | 63.27 ms |!
!

user_summary_by_statement_latency view
mysql> select * from user_summary_by_statement_latencyG!
*************************** 1. row ***************************!
user: mark!
total: 176!
total_latency: 1.26 s!
max_latency: 583.33 ms!
lock_latency: 216.95 ms!
rows_sent: 311!
rows_examined: 307!
rows_affected: 0!
full_scans: 7!

user_summary_by_statement_type view
mysql> select * from user_summary_by_statement_typeG!
*************************** 1. row ***************************!
user: mark!
statement: commit!
total: 2463190!
total_latency: 13.33h!
max_latency: 12.18 s!
lock_latency: 0 ps!
rows_sent: 0!
rows_examined: 0!
rows_affected: 0!
full_scans: 0!

!
• IO by current threads
• Global summaries by file and
class, aggregating by bytes or
latency
• Stream of last file IO events in
raw form
19
IO Summary Views
!
io_by_thread_by_latency
io_global_by_file_by_bytes
io_global_by_file_by_latency
io_global_by_wait_by_bytes
io_global_by_wait_by_latency

io_by_thread_by_latency view
mysql> select * from io_by_thread_by_latencyG!
*************************** 1. row ***************************!
user: main!
total: 1193!
total_latency: 136.45 ms!
min_latency: 731.38 ns!
avg_latency: 269.99 us!
thread_id: 1!
processlist_id: NULL!
*************************** 2. row ***************************!
user: root@localhost!
total: 533!
total_latency: 53.81 ms!
min_latency: 780.39 ns!
avg_latency: 8.41 ms!
thread_id: 23!
processlist_id: 4

io_global_by_file_by_latency view
mysql> select * from io_global_by_file_by_latency limit 1G!
*************************** 1. row ***************************!
file: @@datadir/ibdata1!
total: 1395714!
total_latency: 00:28:53.06!
count_read: 1006!
read_latency: 4.51 s!
count_write: 1326529!
write_latency: 33.39 s!
count_misc: 68179!
misc_latency: 00:28:15.16

!
• Object overview
• Table usage statistics
• Index usage statistics
• Following show users only
23
Schema Analysis Views
schema_index_statistics
schema_object_overview
schema_table_statistics
schema_table_statistics_with_buffer
schema_tables_with_full_table_scans
schema_unused_indexes

schema_table_statistics view
mysql> select * from schema_table_statistics limit 1G!
*************************** 1. row ***************************!
table_schema: mem__quan!
table_name: normalized_statements_by_server_by_schema_data!
rows_fetched: 239685!
fetch_latency: 17.10 s!
rows_inserted: 1102895!
insert_latency: 00:52:18.10!
rows_updated: 55910!
update_latency: 00:02:28.62!
rows_deleted: 17899!
delete_latency: 3.98 s
io_read_requests: 20639!
io_read: 324.94 MiB!
io_read_latency: 00:03:04.10!
io_write_requests: 1965973!
io_write: 40.36 GiB!
io_write_latency: 25.46 s!
io_misc_requests: 18217!
io_misc_latency: 00:14:06.02

schema_index_statistics view
mysql> select * from schema_index_statistics limit 1G!
*************************** 1. row ***************************!
table_schema: mem__inventory!
table_name: mysqlconnectionconfiguration!
index_name: PRIMARY!
rows_selected: 131399!
select_latency: 00:07:05.03!
rows_inserted: 0!
insert_latency: 0 ps!
rows_updated: 41608!
update_latency: 21.96 s!
rows_deleted: 0!
delete_latency: 0 ps

schema_tables_with_full_table_scans view
mysql> select * from schema_tables_with_full_table_scans limit 10;!
+--------------------+--------------------------------+-------------------+-----------+!
| object_schema | object_name | rows_full_scanned | latency |!
+--------------------+--------------------------------+-------------------+-----------+!
| mem30__instruments | fsstatistics | 10207042 | 13.10 s |!
| mem30__instruments | preparedstatementapidata | 436428 | 973.27 ms |!
| mem30__instruments | mysqlprocessactivity | 411702 | 282.07 ms |!
| mem30__instruments | querycachequeriesincachedata | 374011 | 767.15 ms |!
| mem30__instruments | rowaccessesdata | 322321 | 1.55 s |!
| mem30__instruments | connectionsmaxdata | 301242 | 857.63 ms |!
| mem30__instruments | innodbdatadictionarymemorydata | 292564 | 495.38 ms |!
| mem30__instruments | innodbbufferpooldata | 277112 | 1.95 s |!
| mem30__instruments | avgrowaccessesdata | 269236 | 1.25 s |!
| mem30__instruments | innodbrowdetailsdata | 248208 | 653.25 ms |!
+--------------------+--------------------------------+-------------------+-----------+

!
• Wait summaries by class
• Wait details per:
• User
• Host
• Globally
28
Wait Analysis Views
wait_classes_global_by_avg_latency
wait_classes_global_by_latency
waits_by_host_by_latency
waits_by_user_by_latency
waits_global_by_latency
!

waits_global_by_latency view
mysql> select * from waits_global_by_latency limit 10;!
+--------------------------------------+----------+---------------+-------------+-------------+!
| events | total | total_latency | avg_latency | max_latency |!
+--------------------------------------+----------+---------------+-------------+-------------+!
| wait/io/table/sql/handler | 24196659 | 1.75h | 259.72 us | 2.29 s |!
| wait/io/file/innodb/innodb_data_file | 5964255 | 1.36h | 822.01 us | 1.49 s |!
| wait/io/file/innodb/innodb_log_file | 2272647 | 00:36:41.37 | 968.64 us | 1.30 s |!
| wait/io/file/myisam/kfile | 5463587 | 00:18:14.16 | 200.26 us | 1.17 s |!
| wait/io/file/myisam/dfile | 1715187 | 00:08:00.18 | 279.96 us | 1.18 s |!
| wait/io/file/sql/binlog | 3722079 | 00:03:23.71 | 54.73 us | 1.42 s |!
| wait/lock/table/sql/handler | 10074274 | 00:01:56.63 | 11.58 us | 186.90 ms |!
| wait/io/socket/sql/client_connection | 3879827 | 25.36 s | 6.54 us | 219.25 ms |!
| wait/io/file/sql/FRM | 43994 | 3.27 s | 74.35 us | 80.43 ms |!
| wait/io/file/sql/dbopt | 116765 | 1.29 s | 11.03 us | 63.27 ms |!
+--------------------------------------+----------+---------------+-------------+-------------+
InnoDB only instance, this MyISAM IO is all temporary tables, focus tuning there!

waits_by_user_by_latency view
mysql> select * from waits_by_user_by_latency;!
+------+--------------------------------------+----------+---------------+-------------+-------------+!
| user | event | total | total_latency | avg_latency | max_latency |!
+------+--------------------------------------+----------+---------------+-------------+-------------+!
| mark | wait/io/file/myisam/dfile | 19540 | 215.20 ms | 11.01 us | 120.79 ms |!
| mark | wait/io/file/myisam/kfile | 501 | 131.58 ms | 262.63 us | 57.74 ms |!
| mark | wait/io/file/sql/dbopt | 2 | 17.29 us | 8.64 us | 9.17 us |!
| root | wait/io/table/sql/handler | 24189319 | 1.74h | 258.77 us | 2.29 s |!
| root | wait/io/file/innodb/innodb_log_file | 2162650 | 00:30:52.87 | 856.76 us | 1.30 s |!
| root | wait/io/file/myisam/kfile | 5460992 | 00:18:12.83 | 200.11 us | 1.17 s |!
| root | wait/io/file/myisam/dfile | 1694624 | 00:07:59.50 | 282.95 us | 1.18 s |!
| root | wait/io/file/sql/binlog | 3711637 | 00:03:23.16 | 54.74 us | 1.42 s |!
| root | wait/io/file/innodb/innodb_data_file | 22577 | 00:03:05.73 | 8.23 ms | 492.23 ms |!
| root | wait/lock/table/sql/handler | 10069000 | 00:01:56.59 | 11.58 us | 186.90 ms |!
……
root is doing the most temporary table IO

!
• Statement overview
• Find statements by:
• Those with errors
• Those with full table scans
• Those creating temp tables
• Those that cause sorting
• With latency in 95th %ile
31
Statement Analysis Views
statement_analysis
statements_with_errors_or_warnings
statements_with_full_table_scans
statements_with_runtimes_in_95th_p
ercentile
statements_with_sorting
statements_with_temp_tables

statement_analysis view
mysql> select * from statement_analysis limit 2G!
*************************** 1. row ***************************!
query: INSERT INTO `mem30__quan` . `n ... nDuration` = IF ( VALUES ( ...!
db: mem!
full_scan:!
exec_count: 4657!
err_count: 0!
warn_count: 0!
max_latency: 10.54 s!
avg_latency: 50.98 ms!
lock_latency: 00:03:00.93!
rows_sent: 0!
rows_sent_avg: 0!
rows_examined: 0!
rows_examined_avg: 0!
rows_affected: 4794!
rows_affected_avg: 1
tmp_tables: 0!
tmp_disk_tables: 0!
rows_sorted: 0!
sort_merge_passes: 0!
digest: b98bfe333642e8e4e72c73515810d865!
first_seen: 2014-09-24 11:27:01!
last_seen: 2014-09-24 11:53:00

statements_with_errors_or_warnings view
mysql> select * from statements_with_errors_or_warnings limit 1G!
*************************** 1. row ***************************!
query: CREATE TEMPORARY TABLE IF NOT ... _logs` ( `id` INT8 NOT NULL )!
db: mem!
exec_count: 1725!
errors: 1725!
error_pct: 100.0000!
warnings: 0!
warning_pct: 0.0000!
first_seen: 2014-05-20 10:42:32!
last_seen: 2014-05-21 18:39:22!
digest: 51fb979dbc3910a6294c7cdabd7839c3

statements_with_temp_tables view
mysql> select * from statements_with_temp_tables limit 1G!
*************************** 1. row ***************************!
query: SELECT * FROM ( SELECT `digest ... ` ,
`sum_no_index_used` AS ...!
db: mysql!
exec_count: 68!
total_latency: 2.31 s!
memory_tmp_tables: 476!
disk_tmp_tables: 204!
avg_tmp_tables_per_query: 7!
tmp_tables_to_disk_pct: 43!
first_seen: 2014-09-24 11:26:18!
last_seen: 2014-09-24 12:33:00!
digest: 50761c6a1818824328745d8a136b9ed6

statements_with_full_table_scans view
mysql> select * from statements_with_full_table_scans limit 1G!
*************************** 1. row ***************************!
query: SELECT `pojotimese0_` . `id` A ...
ty_timeseries` `pojotimese0_`!
db: mem!
exec_count: 1!
total_latency: 940.89 us!
no_index_used_count: 1!
no_good_index_used_count: 0!
no_index_used_pct: 100!
rows_sent: 116!
rows_examined: 116!
rows_sent_avg: 116!
rows_examined_avg: 116!
first_seen: 2014-09-24 11:25:03!
last_seen: 2014-09-24 11:25:03!
digest: f81b5ce10baee9be754cf35fd245a516

!
• Better SHOW PROCESSLIST
• No mutex contention
• Live statistics for query
36
Miscellaneous Views
processlist
!

processlist view
mysql> select * from processlistG!
*************************** 1. row ***************************!
thd_id: 7890!
conn_id: 7870!
user: root@localhost!
db: mem!
command: Query!
state: update!
time: 0!
current_statement: /* mem dbpool.default */ inser ...<truncated>!
lock_latency: 0 ps!
rows_examined: 0!
rows_sent: 0!
rows_affected: 0!
tmp_tables: 0!
!
!
tmp_disk_tables: 0!
full_scan: NO!
last_statement: NULL!
last_statement_latency: NULL!
last_wait: wait/io/table/sql/handler!
last_wait_latency: Still Waiting!
source: handler.cc:7274

!
• Make output human readable
• Format time appropriately
• Format bytes appropriately
• Truncate output for large
width values for CLI
• Extract object names
• Dump a thread stack
• Check instrumented actors
39
Functions
format_time
format_bytes
format_path
format_statement
extract_table_from_file_name
extract_schema_from_file_name
ps_thread_stack
ps_is_account_enabled
!

format_time() function
mysql> select format_time(23849723429) as time!
-> union select format_time(8327423749233)!
-> union select format_time(83274237492335);!
+-------------+!
| time |!
+-------------+!
| 23.85 ms |!
| 8.33 s |!
| 00:01:23.27 |!
+-------------+!
!
!

format_bytes() function
mysql> select format_bytes(23423) as bytes!
-> union select format_bytes(23432423)!
-> union select format_bytes(42839479283)!
-> union select format_bytes(2293848203489);!
+-----------+!
| bytes |!
+-----------+!
| 22.87 KiB |!
| 22.35 MiB |!
| 39.90 GiB |!
| 2.09 TiB |!
+-----------+!

Performance Schema Config Helper Procedures
• ps_setup_show_disabled() / ps_setup_show_enabled()
• ps_setup_disable_thread() / ps_setup_enable_thread()
• ps_setup_disable_background_threads() /
ps_setup_enable_background_threads()
• ps_setup_disable_instrument() / ps_setup_enable_instrument()
• ps_setup_disable_consumer() / ps_setup_enable_consumer()
• ps_setup_save() / ps_setup_reload_saved()
• ps_setup_reset_to_default() / ps_truncate_all_tables()

!
• Dump all P_S data to a dot
graph file to trace a thread
• Look in the statement history
table to capture more info on
a statement digest
43
Statement Tracing Procedures
ps_trace_thread
ps_trace_statement_digest
ps_statement_avg_latency_histogram
!

ps_trace_statement_digest procedure
• ps_trace_statement_digest() analyses live traffic looking for
certain statement digest for a period of time
• Captures statistics on each matching statement it finds
• Returns a report of the captured stats
• An overall summary
• A break down for the longest running example
• An EXPLAIN (if the statement is not truncated)

• ps_trace_statement_digest() parameters
• in_digest The statement digest to analyse
• in_runtime How long to run analysis for
• in_interval How often to snapshot data
• in_start_fresh Whether to truncate P_S tables first
• in_auto_enable Whether to auto enable required config

ps_trace_statement_digest procedure example
!!!
mysql> call analyze_statement_digest('6134e9d6f25eb8e6cddf11f6938f202a', 60, 1, true, true);
+--------------------+
| SUMMARY STATISTICS |
+--------------------+
| SUMMARY STATISTICS |
+--------------------+
1 row in set (59.93 sec)
!
+------------+-----------+-----------+-----------+---------------+------------+------------+
| executions | exec_time | lock_time | rows_sent | rows_examined | tmp_tables | full_scans |
+------------+-----------+-----------+-----------+---------------+------------+------------+
| 360 | 1.41 s | 138.39 ms | 720 | 0 | 0 | 0 |
+------------+-----------+-----------+-----------+---------------+------------+------------+
1 row in set (59.93 sec)
!
+--------------------------------+-------+-----------+
| event_name | count | latency |
+--------------------------------+-------+-----------+
| stage/sql/Sending data | 14 | 1.10 s |
| stage/sql/update | 198 | 667.34 ms |
| stage/sql/removing tmp table | 9 | 240.48 ms |
... Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

!!!
+---------------------------+
| LONGEST RUNNING STATEMENT |
+---------------------------+
| LONGEST RUNNING STATEMENT |
+---------------------------+
!
1 row in set (59.95 sec) +-----------+-----------+-----------+-----------+---------------+------------+-----------+
| thread_id | exec_time | lock_time | rows_sent | rows_examined | tmp_tables | full_scan |
+-----------+-----------+-----------+-----------+---------------+------------+-----------+
| 23277 | 77.64 ms | 97.00 us | 2 | 0 | 0 | 0 |
+-----------+-----------+-----------+-----------+---------------+------------+-----------+
!
1 row in set (59.95 sec) +-------------------------------------------------------------------------------------------+
| sql_text |
+-------------------------------------------------------------------------------------------+
| /* mem dbpool.default */ insert into `mem__quan`.`normalized_statements_by_server_by_schema`
(firstSeen, lastSeen, normalized_statement_id, `schema`, server, id) values (1378983745000,
1378998600000, x'808ACEB88FC4B45BC47C4FE9D86C7F26', 'mem', '753c939e-1b99-11e3-b6d4-bc761a1f4f2f',
x'7CFE81F98B1E3FE0895D1AA2C39B326D') ON DUPLICATE KEY UPDATE ...
+-------------------------------------------------------------------------------------------+
... Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

ps_trace_thread procedure
• ps_trace_thread() monitors a specific thread for a period
• Captures as much information on the thread activity as possible
• Returns a “dot” formatted file, that can graph the event hierarchy
• http://en.wikipedia.org/wiki/DOT_(graph_description_language)

• ps_trace_statement_digest() parameters
• in_thread_id The thread to analyse
• in_outfile The file to dump the data to (INTO OUTFILE)
• in_max_runtime How long to run analysis for
• in_interval How often to snapshot for data
• in_start_fresh Whether to truncate P_S tables first
• in_auto_setup Whether to auto enable required config
• in_debug Whether to also print debug info (source info)

ps_trace_thread procedure example
mysql> call ps_trace_thread(27768, '/tmp/stack_27768.dot', 60, 0.1, true, true, true);
+------------------------------------------------+
| Info |
+------------------------------------------------+
| Data collection starting for THREAD_ID = 27768 |
+------------------------------------------------+
1 row in set (4.82 sec) !
+---------------------------------------------+
| Info |
+---------------------------------------------+
| Stack trace written to /tmp/stack_27768.dot |
+---------------------------------------------+
+--------------------------------------------------------+
| Convert to PDF |
+--------------------------------------------------------+
| dot -Tpdf -o /tmp/stack_27768.pdf /tmp/stack_27768.dot |
+--------------------------------------------------------+
+--------------------------------------------------------+
| Convert to PNG |
+--------------------------------------------------------+
| dot -Tpng -o /tmp/stack_27768.png /tmp/stack_27768.dot |
+--------------------------------------------------------+
1 row in set (60.90 sec)+
!

cerberus:~ mark$ more Documents/statement_graphs/deletes.dot!
digraph events {!
graph [rankdir=LR, nodesep="0.10"];!
node [label="N"];!
graph [bb="0,0,1860,17476"];!
1 [label="(0.20μ) mysys/THR_LOCK_threadsn", style=filled, color=lightskyblue, pos="209,18", width="3.19", height="0.50"];!
2 [label="(0.18μ) sql/THD::LOCK_thd_datan", style=filled, color=lightskyblue, pos="209,61", width="3.06", height="0.50"];!
3 [label="(0.24μ) sql/hash_filo::lockn", style=filled, color=lightskyblue, pos="209,104", width="2.42", height=“0.50"];!
4 [label="(0.31μ) sql/LOGGER::LOCK_logger - read_lockn", style=filled, color=orchid, pos="209,147", width="4.22",
height="0.50"];!
5 [label="(0.08μ) sql/LOG::LOCK_logn", style=filled, color=lightskyblue, pos="209,190", width="2.64", height="0.50"];!
6 [label="(12.97μ) wait/io/file/sql/query_log - write 49 bytesn/Users/mark/mysql/lp-mysql-trunk/mysql-test/var/mysqld.1/
mysqld.logn", style=filled, color=red, shape=box, pos="209,235", width="5.78", height="0.56"];!
7 [label="(176.14μ) sql/selectnselect @@version_comment limit 1nerrors: 0nwarnings: 0nlock time: 0.00μnrows affected:
0nrows sent:!
209,18", width="3.19", height="0.50"];mp disk tables: 0nselect scan: 0nselect full join: :!
2 [label="(0.18μ) sql/THD::LOCK_thd_datan", style=filled, color=lightskyblue, pos="209,61", width="3.06", height="0.50"];!
3 [label="(0.24μ) sql/hash_filo::lockn", style=filled, color=lightskyblue, pos="209,104", width="2.42", height="0.50"];!
4 [label="(0.31μ) sql/LOGGER::LOCK_logger - read_lockn", style=filled, color=orchid, pos="209,147", width="4.22",
height="0.50"];!
5 [label="(0.08μ) sql/LOG::LOCK_logn", style=filled, color=lightskyblue, pos="209,190", width="2.64", height="0.50"];!
……! !

MySQL 5.7
!
Procedures
Transactions
Statements
Stages
Waits

The MySQL SYS Schema

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