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I have a vps server with os centos 6.7 64x, 2 cpu's and 3gb ram, and I use it exclusively for a WP MU (Memory limit: 512 MByte/Memory usage: 53.97 MByte).

I use mostly myisam and have about 30 subsites, most of them are blogs and there some e-shops. The visits in all of these sites everydays is about 100 to 250 people on each site. And sometimes, some sites might 400 to 800 visits. I have added the plugin w3tc and stil I feel that it goes slow for the guests and for the logged in users too.

How can I understand how much memory and cpu I need everytime so I won't have any problems and what else do you need so I can give you a better image of my server?

My nano /etc/my.cnf

[myisamchk]
read_buffer=16M
key_buffer=32M
write_buffer=16M
sort_buffer=32M
[mysqld_safe]
open_files_limit=8192
log-error="/var/log/mysqld.log"
pid-file="/var/run/mysqld/mysqld.pid"
[mysqld]
slow-query-log=1
slow-query-log-file="/var/log/mysql/slow.log"
long_query_time=4
log_queries_not_using_indexes=1
local-infile=0
join_buffer_size=10M
connect_timeout=10
read_buffer_size=1M
key_buffer=16M
key_buffer_size=70M
# old_passwords=1
max_allowed_packet=268435456
interactive_timeout=25
max_connect_errors=10
max_connections=256
wait_timeout=1000
query_cache_size=0
query_cache_type=OFF
user=mysql
thread_cache_size=286
sort_buffer_size=10M
tmp_table_size=256M
max_heap_table_size=256M
table_open_cache=500
query_cache_limit=128M
socket="/var/lib/mysql/mysql.sock"
myisam_sort_buffer_size=32M
datadir="/var/lib/mysql"
default-storage-engine=MyISAM
innodb_file_per_table=1
innodb_buffer_pool_size=134217728
open_files_limit=10000
[isamchk]
read_buffer=16M
key_buffer=32M
write_buffer=16M
sort_buffer=32M
[mysqlhotcopy]
skip-networking
interactive-timeout

And this results of MySQLTuner

 >>  MySQLTuner 1.6.1 - Major Hayden <major@mhtx.net>
 >>  Bug reports, feature requests, and downloads at http://mysqltuner.com/
 >>  Run with '--help' for additional options and output filtering
[--] Skipped version check for MySQLTuner script
[OK] Currently running supported MySQL version 10.0.22-MariaDB-log
[OK] Operating on 64-bit architecture

-------- Storage Engine Statistics -------------------------------------------
[--] Status: +ARCHIVE +Aria +BLACKHOLE +CSV +FEDERATED +InnoDB +MRG_MyISAM
[--] Data in MyISAM tables: 501M (Tables: 869)
[--] Data in InnoDB tables: 656K (Tables: 16)
[!!] Total fragmented tables: 37

-------- Security Recommendations  -------------------------------------------
[OK] There are no anonymous accounts for any database users
[OK] All database users have passwords assigned
[--] There are 605 basic passwords in the list.

-------- Performance Metrics -------------------------------------------------
[--] Up for: 23h 28m 37s (1M q [12.900 qps], 36K conn, TX: 42B, RX: 1B)
[--] Reads / Writes: 82% / 18%
[--] Binary logging is disabled
[--] Total buffers: 598.0M global + 21.5M per thread (256 max threads)
[OK] Maximum reached memory usage: 1.0G (33.48% of installed RAM)
[!!] Maximum possible memory usage: 6.0G (198.89% of installed RAM)
[!!] Slow queries: 7% (86K/1M)
[OK] Highest usage of available connections: 7% (20/256)
[OK] Aborted connections: 0.18%  (65/36559)
[!!] Query cache is disabled
[OK] Sorts requiring temporary tables: 0% (0 temp sorts / 143K sorts)
[!!] Joins performed without indexes: 324
[!!] Temporary tables created on disk: 43% (37K on disk / 87K total)
[OK] Thread cache hit rate: 99% (20 created / 36K connections)
[!!] Table cache hit rate: 2% (500 open / 23K opened)
[OK] Open file limit used: 12% (998/8K)
[OK] Table locks acquired immediately: 99% (1M immediate / 1M locks)

-------- MyISAM Metrics -----------------------------------------------------
[!!] Key buffer used: 18.8% (13M used / 73M cache)
[OK] Key buffer size / total MyISAM indexes: 70.0M/145.8M
[OK] Read Key buffer hit rate: 99.4% (23M cached / 131K reads)
[!!] Write Key buffer hit rate: 30.6% (347K cached / 241K writes)

-------- InnoDB Metrics -----------------------------------------------------
[--] InnoDB is enabled.
[OK] InnoDB buffer pool / data size: 128.0M/656.0K
[!!] InnoDB buffer pool <= 1G and innodb_buffer_pool_instances(!=1).
[!!] InnoDB Used buffer: 6.36% (521 used/ 8191 total)
[OK] InnoDB Read buffer efficiency: 97.13% (17216 hits/ 17724 total)
[!!] InnoDB Write buffer efficiency: 0.00% (0 hits/ 1 total)
[OK] InnoDB log waits: 0.00% (0 waits / 21 writes)

-------- AriaDB Metrics -----------------------------------------------------
[--] AriaDB is disabled.

-------- Replication Metrics -------------------------------------------------
[--] No replication slave(s) for this server.
[--] This is a standalone server..

-------- Recommendations -----------------------------------------------------
General recommendations:
    Run OPTIMIZE TABLE to defragment tables for better performance
    MySQL started within last 24 hours - recommendations may be inaccurate
    Reduce your overall MySQL memory footprint for system stability
    Adjust your join queries to always utilize indexes
    Temporary table size is already large - reduce result set size
    Reduce your SELECT DISTINCT queries without LIMIT clauses
    Increase table_open_cache gradually to avoid file descriptor limits
    Read this before increasing table_open_cache over 64: http://bit.ly/1mi7c4C
    Beware that open_files_limit (8192) variable
    should be greater than table_open_cache ( 500)
Variables to adjust:
  *** MySQL's maximum memory usage is dangerously high ***
  *** Add RAM before increasing MySQL buffer variables ***
    query_cache_size (>= 8M)
    join_buffer_size (> 10.0M, or always use indexes with joins)
    table_open_cache (> 500)
    innodb_buffer_pool_instances (=1)

When it says "Add RAM before increasing MySQL buffer variables", what do I have to do exactly?

My tail -n 100 /var/log/mysql-slow-queries.log

tail: cannot open `/var/log/mysql-slow-queries.log' for reading: No such file or directory

My tail -n 100 /var/log/mysqld.log (On 0:03:45 and after I gives me data that belong on ip's and sites of mys server. How is this possible?)

160102 19:22:19 [Note] InnoDB: Waiting for purge to start
160102 19:22:19 [Note] InnoDB:  Percona XtraDB (http://www.percona.com) 5.6.26-74.0 started; log sequence number 27983072465
160102 19:22:19 [Note] Plugin 'FEEDBACK' is disabled.
160102 19:22:19 [Note] Server socket created on IP: '::'.
160102 19:22:19 [Note] /usr/sbin/mysqld: ready for connections.
Version: '10.0.22-MariaDB-log'  socket: '/var/lib/mysql/mysql.sock'  port: 3306  MariaDB Server
160102 21:13:47 [Note] /usr/sbin/mysqld: Normal shutdown

160102 21:13:47 [Note] Event Scheduler: Purging the queue. 0 events
160102 21:13:47 [Note] InnoDB: FTS optimize thread exiting.
160102 21:13:47 [Note] InnoDB: Starting shutdown...
160102 21:13:49 [Note] InnoDB: Shutdown completed; log sequence number 27983072475
160102 21:13:49 [Note] /usr/sbin/mysqld: Shutdown complete

160102 21:13:49 mysqld_safe mysqld from pid file /var/lib/mysql/server.mywebsite.com.com.pid ended
160102 21:13:50 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
160102 21:13:50 [Note] /usr/sbin/mysqld (mysqld 10.0.22-MariaDB-log) starting as process 2670 ...
160102 21:13:50 [Note] InnoDB: Using mutexes to ref count buffer pool pages
160102 21:13:50 [Note] InnoDB: The InnoDB memory heap is disabled
160102 21:13:50 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
160102 21:13:50 [Note] InnoDB: Memory barrier is not used
160102 21:13:50 [Note] InnoDB: Compressed tables use zlib 1.2.3
160102 21:13:50 [Note] InnoDB: Using Linux native AIO
160102 21:13:50 [Note] InnoDB: Using CPU crc32 instructions
160102 21:13:50 [Note] InnoDB: Initializing buffer pool, size = 128.0M
160102 21:13:50 [Note] InnoDB: Completed initialization of buffer pool
160102 21:13:50 [Note] InnoDB: Highest supported file format is Barracuda.
160102 21:13:50 [Note] InnoDB: 128 rollback segment(s) are active.
160102 21:13:50 [Note] InnoDB: Waiting for purge to start
160102 21:13:50 [Note] InnoDB:  Percona XtraDB (http://www.percona.com) 5.6.26-74.0 started; log sequence number 27983072475
160102 21:13:50 [Note] Plugin 'FEEDBACK' is disabled.
160102 21:13:50 [Note] Server socket created on IP: '::'.
160102 21:13:50 [Note] /usr/sbin/mysqld: ready for connections.
Version: '10.0.22-MariaDB-log'  socket: '/var/lib/mysql/mysql.sock'  port: 3306  MariaDB Server
160102 23:13:09 [Note] /usr/sbin/mysqld: Normal shutdown

160102 23:13:09 [Note] Event Scheduler: Purging the queue. 0 events
160102 23:13:09 [Note] InnoDB: FTS optimize thread exiting.
160102 23:13:09 [Note] InnoDB: Starting shutdown...
160102 23:13:11 [Note] InnoDB: Shutdown completed; log sequence number 27983072485
160102 23:13:11 [Note] /usr/sbin/mysqld: Shutdown complete

160102 23:13:11 mysqld_safe mysqld from pid file /var/lib/mysql/server.mywebsite.com.pid ended
160102 23:13:11 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
160102 23:13:11 [Note] /usr/sbin/mysqld (mysqld 10.0.22-MariaDB-log) starting as process 8751 ...
160102 23:13:11 [Note] InnoDB: Using mutexes to ref count buffer pool pages
160102 23:13:11 [Note] InnoDB: The InnoDB memory heap is disabled
160102 23:13:11 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
160102 23:13:11 [Note] InnoDB: Memory barrier is not used
160102 23:13:11 [Note] InnoDB: Compressed tables use zlib 1.2.3
160102 23:13:11 [Note] InnoDB: Using Linux native AIO
160102 23:13:11 [Note] InnoDB: Using CPU crc32 instructions
160102 23:13:11 [Note] InnoDB: Initializing buffer pool, size = 128.0M
160102 23:13:11 [Note] InnoDB: Completed initialization of buffer pool
160102 23:13:11 [Note] InnoDB: Highest supported file format is Barracuda.
160102 23:13:11 [Note] InnoDB: 128 rollback segment(s) are active.
160102 23:13:11 [Note] InnoDB: Waiting for purge to start
160102 23:13:11 [Note] InnoDB:  Percona XtraDB (http://www.percona.com) 5.6.26-74.0 started; log sequence number 27983072485
160102 23:13:11 [Note] Plugin 'FEEDBACK' is disabled.
160102 23:13:11 [Note] Server socket created on IP: '::'.
160102 23:13:11 [Note] /usr/sbin/mysqld: ready for connections.
Version: '10.0.22-MariaDB-log'  socket: '/var/lib/mysql/mysql.sock'  port: 3306  MariaDB Server
160102 23:16:09 [Note] /usr/sbin/mysqld: Normal shutdown

160102 23:16:09 [Note] Event Scheduler: Purging the queue. 0 events
160102 23:16:09 [Note] InnoDB: FTS optimize thread exiting.
160102 23:16:09 [Note] InnoDB: Starting shutdown...
160102 23:16:11 [Note] InnoDB: Shutdown completed; log sequence number 27983072495
160102 23:16:11 [Note] /usr/sbin/mysqld: Shutdown complete

160102 23:16:11 mysqld_safe mysqld from pid file /var/lib/mysql/server.mywebsite.com.pid ended
160102 23:16:11 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
160102 23:16:11 [Note] /usr/sbin/mysqld (mysqld 10.0.22-MariaDB-log) starting as process 10571 ...
160102 23:16:11 [Note] InnoDB: Using mutexes to ref count buffer pool pages
160102 23:16:11 [Note] InnoDB: The InnoDB memory heap is disabled
160102 23:16:11 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
160102 23:16:11 [Note] InnoDB: Memory barrier is not used
160102 23:16:11 [Note] InnoDB: Compressed tables use zlib 1.2.3
160102 23:16:11 [Note] InnoDB: Using Linux native AIO
160102 23:16:11 [Note] InnoDB: Using CPU crc32 instructions
160102 23:16:11 [Note] InnoDB: Initializing buffer pool, size = 128.0M
160102 23:16:11 [Note] InnoDB: Completed initialization of buffer pool
160102 23:16:11 [Note] InnoDB: Highest supported file format is Barracuda.
160102 23:16:11 [Note] InnoDB: 128 rollback segment(s) are active.
160102 23:16:11 [Note] InnoDB: Waiting for purge to start
160102 23:16:11 [Note] InnoDB:  Percona XtraDB (http://www.percona.com) 5.6.26-74.0 started; log sequence number 27983072495
160102 23:16:11 [Note] Plugin 'FEEDBACK' is disabled.
160102 23:16:11 [Note] Server socket created on IP: '::'.
160102 23:16:11 [Note] /usr/sbin/mysqld: ready for connections.
Version: '10.0.22-MariaDB-log'  socket: '/var/lib/mysql/mysql.sock'  port: 3306  MariaDB Server
160103  0:03:45 [Warning] IP address '222.186.30.119' could not be resolved: Name or service not known
160103  4:45:12 [Warning] IP address '222.186.50.221' could not be resolved: Name or service not known
160103  8:02:49 [Warning] IP address '123.57.67.126' could not be resolved: Name or service not known
160103 10:22:34 [Warning] Hostname 'mx.campprice.com' does not resolve to '216.99.158.156'.
160103 10:22:34 [Note] Hostname 'mx.campprice.com' has the following IP addresses:
160103 10:22:34 [Note]  - 5.2.16.155
160103 11:37:24 [Warning] IP address '1.93.1.91' could not be resolved: Name or service not known
160103 14:38:25 [Warning] IP address '171.92.207.61' could not be resolved: Name or service not known
160103 15:06:41 [Warning] IP address '221.231.139.150' could not be resolved: Name or service not known
160103 16:41:46 [Warning] IP address '5.39.222.253' could not be resolved: Name or service not known

My tail -n 100 /var/log/mysql/slow.log

My ls -l /var/lib/mysql

   total 125260
drwxr-x--x 16 mysql mysql     4096 Dec 29 03:27 ./
drwxr-xr-x 20 root  root      4096 Dec 29 03:12 ../
drwx------  2 mysql mysql    57344 Dec 14 19:15 tsimis_vemal/
-rw-rw----  1 mysql mysql    16384 Dec 28 01:49 aria_log.00000001
-rw-rw----  1 mysql mysql       52 Dec 28 01:49 aria_log_control
-rw-rw----  1 mysql mysql       56 Dec 11 15:23 auto.cnf
drwx------  2 mysql mysql     4096 Dec  7 23:46 cphulkd/
drwx------  2 mysql mysql     4096 Dec 28 05:30 eximstats/
-rw-rw----  1 mysql mysql 27262976 Dec 28 20:43 ibdata1
-rw-rw----  1 mysql mysql 50331648 Dec 28 20:43 ib_logfile0
-rw-rw----  1 mysql mysql 50331648 Dec 11 15:23 ib_logfile1
drwx------  2 mysql mysql     4096 Dec  7 23:46 tsarmil_wordpress/
drwx------  2 mysql mysql     4096 Dec  7 23:46 leechprotect/
drwx------  2 mysql mysql     4096 Dec  7 23:46 modsec/
-rw-rw----  1 mysql mysql        0 Dec 11 15:25 multi-master.info
drwx--x--x  2 mysql mysql     4096 Dec 11 15:25 mysql/
-rw-rw----  1 mysql mysql        0 Nov 21 22:17 mysql-bin.index
-rw-r-----  1 mysql mysql    18229 Nov 21 22:18 mysql-error.log
srwxrwxrwx  1 mysql mysql        0 Dec 28 01:49 mysql.sock=
-rw-r--r--  1 mysql mysql       15 Dec 11 15:25 mysql_upgrade_info
drwx------  2 mysql mysql     4096 Dec 11 15:25 performance_schema/
drwx------  2 mysql mysql     4096 Dec  7 23:46 roundcube/
-rw-r--r--  1 mysql mysql     1021 Dec 11 15:24 RPM_UPGRADE_HISTORY
-rw-r--r--  1 mysql mysql      526 Dec 11 15:24 RPM_UPGRADE_MARKER-LAST
-rw-r-----  1 mysql mysql    80432 Nov 15 13:35 server.mydomain.com.err
-rw-rw----  1 mysql mysql        5 Dec 28 01:49 server.mydomain.com.pid
-rw-rw----  1 mysql mysql        0 Nov 21 01:33 slow.log
drwx------  2 mysql mysql    36864 Dec 28 01:41 dumdum_dbsp/
drwx------  2 mysql mysql    36864 Dec 23 00:28 dumdum_demoplayer/
drwx------  2 mysql mysql     4096 Dec 10 01:21 dumdum_mudemodb/
drwx------  2 mysql mysql     4096 Dec  7 23:46 dumdum_ttvelmor/
drwx------  2 mysql mysql     4096 Dec 15 03:27 whmxfer/

My top

top - 22:53:01 up 5 days, 18:39,  1 user,  load average: 1.07, 0.85, 0.59
Tasks:  72 total,   2 running,  67 sleeping,   0 stopped,   3 zombie
Cpu(s): 22.3%us,  1.5%sy,  0.0%ni, 76.2%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Mem:   3145728k total,  2348472k used,   797256k free,        0k buffers
Swap:  3145728k total,   175068k used,  2970660k free,  2097268k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
31449 account1  20   0  304m 129m  74m R 32.3  4.2   1:58.94 php
32640 account1  20   0  314m 135m  72m S 10.3  4.4   0:17.33 php
10571 mysql     20   0  988m 105m 8112 S  1.0  3.4  31:31.90 mysqld
  582 root      20   0 99800 4340 3256 S  0.3  0.1   0:00.08 sshd
 1111 root      20   0  112m  440  360 S  0.3  0.0   0:01.20 crond
 1138 root      20   0  108m  752  648 S  0.3  0.0   0:07.40 varnishd
23350 nobody    20   0 63572 4404 2104 S  0.3  0.1   0:00.70 httpd
25143 nobody    20   0 63564 4396 2112 S  0.3  0.1   0:00.45 httpd
    1 root      20   0 19236  984  844 S  0.0  0.0   0:01.97 init
    2 root      20   0     0    0    0 S  0.0  0.0   0:00.00 kthreadd/1227
    3 root      20   0     0    0    0 S  0.0  0.0   0:00.00 khelper/1227
  147 root      16  -4 10648  352  348 S  0.0  0.0   0:00.00 udevd
  451 dovecot   20   0 29576 2228 1672 S  0.0  0.1   0:00.01 auth
  554 root      20   0     0    0    0 Z  0.0  0.0   0:00.00 cpsrvd (SSL) -  <defunct>
  555 root      20   0     0    0    0 Z  0.0  0.0   0:00.00 cpsrvd (SSL) -  <defunct>
  583 sshd      20   0 67784 1652  848 S  0.0  0.1   0:00.00 sshd
  595 root      20   0 67784 3256 2500 S  0.0  0.1   0:00.00 sshd
  596 sshd      20   0 67784 1560  804 S  0.0  0.0   0:00.00 sshd
  728 root      20   0  179m 4380  800 S  0.0  0.1   0:24.25 rsyslogd
  749 named     20   0  233m 3388 1548 S  0.0  0.1   0:16.58 named
  767 nscd      20   0  941m 1420  984 S  0.0  0.0   0:36.59 nscd
  792 root      20   0 64336  560  460 S  0.0  0.0   0:09.77 sshd
  802 root      20   0 20040  364  360 S  0.0  0.0   0:00.00 xinetd
 1034 root      20   0 18212  844  676 S  0.0  0.0   0:01.74 dovecot
 1039 dovenull  20   0 42644 2748 2544 S  0.0  0.1   0:00.25 pop3-login
 1040 dovenull  20   0 42648 3028 2592 S  0.0  0.1   0:00.43 imap-login
 1041 dovecot   20   0 13472  916  816 S  0.0  0.0   0:00.52 anvil
 1042 root      20   0 13608 1032  872 S  0.0  0.0   0:00.89 log
 1044 dovenull  20   0 42740 2812 2580 S  0.0  0.1   0:00.70 pop3-login
 1045 dovenull  20   0 42788 3056 2620 S  0.0  0.1   0:01.52 imap-login
 1049 root      20   0 14636 1764  948 S  0.0  0.1   0:01.88 config
 1054 root      20   0 66412  284  280 S  0.0  0.0   0:00.00 saslauthd
 1056 root      20   0 66412   32   28 S  0.0  0.0   0:00.00 saslauthd
 1068 mailnull  20   0 70564 2536 2396 S  0.0  0.1   0:01.06 exim
 1077 root      20   0  194m 7072 2752 S  0.0  0.2   0:59.42 /usr/local/cpan
 1089 root      20   0 62448 5596 4212 S  0.0  0.2   0:10.45 httpd
 1098 root      20   0  133m 1432 1364 S  0.0  0.0   0:00.50 pure-ftpd
 1100 root      20   0  132m 1352 1304 S  0.0  0.0   0:00.44 pure-authd
 1183 root      20   0 19428  384  364 S  0.0  0.0   0:00.00 atd
 1540 root      20   0  105m 3092 1120 S  0.0  0.1   0:06.81 cpsrvd (SSL) -
 1546 root      20   0 32692 1680 1424 S  0.0  0.1   0:01.13 queueprocd - wa
 1562 root      20   0 78132 6704 1672 S  0.0  0.2   1:11.63 tailwatchd
 1577 root      20   0 34240 2512 1780 S  0.0  0.1   0:47.76 cPhulkd - proce
 1606 root      20   0  119m 1844  664 S  0.0  0.1   0:02.48 cpdavd - accept
 1617 root      38  18 23664 1684 1128 S  0.0  0.1   0:00.94 cpanellogd - sl
 1639 nobody    20   0  321m  732  556 S  0.0  0.0   0:08.56 memcached
 1646 root      20   0  4068  496  492 S  0.0  0.0   0:00.00 mingetty
 1647 root      20   0  4068  496  492 S  0.0  0.0   0:00.00 mingetty
 7355 root      20   0  219m  75m 3424 S  0.0  2.4   0:42.96 spamd child
10391 root      20   0  9416 1120 1116 S  0.0  0.0   0:00.00 mysqld_safe
20373 root      20   0 13468 1124  932 S  0.0  0.0   0:00.00 ssl-params
23347 root      20   0 76528  11m 2896 S  0.0  0.4   0:00.09 leechprotect
23348 nobody    20   0 62584 2296  760 S  0.0  0.1   0:00.06 httpd
1

[!!] Query cache efficiency: 19.9% (71K cached / 357K selects) [!!] Query cache prunes per day: 250428

Turn off the Query cache:

query_cache_type = OFF
query_cache_size = 0

[!!] Table cache hit rate: 2% (200 open / 8K opened)

How many tables do you have? Sounds like more than 200?? This is sometimes a sign of a bad schema design; please explain why so many.

Meanwhile, change

table_open_cache = 500

The rest of the [!!] are bogus; ignore them.

The only Recommendation of note is

MySQL started within last 24 hours - recommendations may be inaccurate

You do seem to have slow queries. So, use pt-query-digest to summarize /var/log/mysql-slow-queries.log. Come back to us (in a separate thread) with the two worst queries, together with

    SHOW CREATE TABLE
    EXPLAIN SELECT ...

If (when) your dataset grows to, say, twice its current size, some buffer settings should be re-investigated.

Executive summary:

  • Increase table_open_cache
  • Look into improving the 'slow' queries.
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