Posts Tagged ‘queries’

WordPress Plugins to monitor and debug WP enabled plugins – Find Errors / Warnings and Remove WP problematic plugins slowing down your Website (blog) database

Thursday, February 19th, 2015


Recent days, I'm spending a lot of time again trying to optimize my wordpress blog. Optimizing WP for better efficiency is becoming harder and harder task day by day as the website file content data is growing along with SQL databases. Moreover situation gets even worse because the number of plugins enabled on my blog is incrementally growing with time because, there is more and more goodies I'd like to add.
Optimizing WordPress to run for Speed on a server is a whole a lot of art and its a small universe in itself, because as of time of writting this post the count (number) of WordPress available PLUGINS is 36,197 ! 

1. Manually Tracking WordPress  Plugins causing Slow SQL Queries (MySQL bottleneck) issues directly using console / SSH

Because of its open source development and its nice modular design wordpress has turned into a standard for building small, middle sized and large websites (some WordPress based blogs and sites have from 50 000 to 100 000 unique pages!). My blog is still a small WordPress site with only 1676 posts, so I still haven't reached the high volume traffic optimization requirements but still even though I have a relatively good server hardware  8GB RAM / (2×2.70 Ghz Intel CPU) / 500 GB (7400 RPM HDD) at times I see Apache Webservers is unable to properly serve coming requests because of MySQL database (LEFT JOIN) requests being slow to serve (taking up to few seconds to complete) and creating a MySQL table lock, putting all the rest SQL queries to stay in a long unserved queues line, I've realized about this performance issue by using a a mysql cli (command) client and few commands and console command (tool) called mytop (also known as mtop). MyTop refreshes every 3 seconds, so the slow query will immediately stay on screen to view moer info about it press "f" and type the  in query ID.



Finally it is very useful to run  for a while MySQL server logging to /var/log/mysql/slow-query.log:
Slow query is enabled (on my Debian 7 Wheezy host) by adding to /etc/mysql/my.cnf
after conf section


vim /etc/mysql/my.cnf
# * Logging and Replication
# Both location gets rotated by the cronjob.
# Be aware that this log type is a performance killer.
# As of 5.1 you can enable the log at runtime!
#general_log_file        = /var/log/mysql/mysql.log
#general_log             = 1
# Error logging goes to syslog due to /etc/mysql/conf.d/mysqld_safe_syslog.cnf.
# Here you can see queries with especially long duration




slow_query_log = 1
slow_query_log_file = /var/log/mysql/slow-query.log
long_query_time = 2


And then to make new mysql configuration load restarted mysql server:


debian-server:~# /etc/init.d/mysql restart
Stopping MySQL database server: mysqld.
Starting MySQL database server: mysqld ..
Checking for tables which need an upgrade, are corrupt or were
not closed cleanly..


Leaving mysql-slow.log to be enabled for 30 minutes to an 1 hrs is a good time to track most problematic slow queries and based on this queries, I took parts of  SQL UPDATE / SELECT / INSERT etc. Db queries which was problematic and grepped throughout /var/www/blog/wp-content/plugin files in order to determine which WordPress Plugin is triggering the slow query, causing blog to hang when too many clients try to see it in browser.

My main problematic SQL query having long execution time  (about 2 to 3 seconds!!!) most commonly occuring in slow-query.log was:


SELECT DISTINCT post_title, ID, post_type, post_name FROM wp_posts wposts LEFT JOIN wp_postmeta wpostmeta ON wposts.ID = wpostmeta.post_id LEFT JOIN wp_term_relationships ON (wposts.ID = wp_term_relationships.object_id) LEFT JOIN wp_term_taxonomy ON (wp_term_relationships.term_taxonomy_id = wp_term_taxonomy.term_taxonomy_id) WHERE (post_type='page' OR (wp_term_taxonomy.taxonomy = 'category' AND wp_term_taxonomy.term_id IN(11))) AND post_status = 'publish' AND LENGTH(post_title)>=5 ORDER BY LENGTH(post_title) ASC LIMIT 500

Because above query uses SQL Column names and Tables which are not hard coded in PHP code, to find out which plugins is most probably to launch this complex LEFT JOIN query, I used a quick bash one-liner:


# cd /var/www/blog/wp-content/plugins


# for i in $(grep -rli 'SELECT DISTINCT' *); do grep -rli 'LEFT JOIN' $i; done 


I wanted to put less load on CPU during grep so looked for string only in .PHP extensioned files with:


 # for i in $(find . -iname '*.php' -exec grep -rli 'SELECT DISTINCT' '{}' \;); do grep -rli 'LEFT JOIN' $i; done

As you can see the complex query is being called from PHP file belonging to one of 3 plugins

  • SEO Automatic Links – this is SEO Smart Links WP plugin (Does internal bliog interlinking in order to boast SEA)
  • WP PostViews – WordPress Post Views plugin (Which allows me to show how many times an article was read in WP Widget menu)
  • Yet Another Related Posts – Which is WP plugin I installed / enabled to show Related posts down on each blog post

2. Basic way to optimize MySQL slow queries (EXPLAIN / SHOW CREATE TABLE)

Now as I have a basic clue on plugins locking my Database, I disabled them one by one while keeping enabled mysql slow query log and viewing queries in mytop and I figure out that actually all of the plugins were causing a short time overheat (lock) on server Database because of LEFT JOINs. Though I really like what this plugins are doing, as they boast SEO and attract prefer to disable them for now and have my blog all the time responsible light fast instead of having a little bit better Search Engine Optimization (Ranking) and loosing many of my visitors because they're annoyed to wait until my articles open

Before disabling I tried to optimize the queries using MySQL EXPLAIN command + SHOW CREATE TABLE (2 commands often used to debug slow SQL queries and find out whether a Column needs to have added INDEX-ing to boast MySQL query).

Just in case if you decide to give them a try here is example on how they're used to debug problematic SQL query:

  1. mysql> explain SELECT DISTINCT post_title, ID, post_type, post_name
  2.     -> FROM wp_posts wposts LEFT JOIN wp_postmeta wpostmeta
  3.     -> ON wposts.ID = wpostmeta.post_id LEFT JOIN wp_term_relationships
  4.     -> ON (wposts.ID = wp_term_relationships.object_id) LEFT JOIN wp_term_taxonomy
  5.     -> ON (wp_term_relationships.term_taxonomy_id = wp_term_taxonomy.term_taxonomy_id)
  6.     -> WHERE (post_type='page'
  7.     -> OR (wp_term_taxonomy.taxonomy = 'category'
  8.     -> AND wp_term_taxonomy.term_id IN(11,15,17)))
  9.     -> AND post_status = 'publish'
  10.     -> AND LENGTH(post_title)>=5
  11.     -> ORDER BY LENGTH(post_title) ASC
  12.     -> LIMIT 500;
  13. +—-+————-+———————–+——–+——————+———+———+———————————————+——+———————————————-+
  14. | id | select_type | table                 | type   | possible_keys    | key     | key_len | ref                                         | rows | Extra                                        |
  15. +—-+————-+———————–+——–+——————+———+———+———————————————+——+———————————————-+
  16. |  1 | SIMPLE      | wposts                | ALL    | type_status_date | NULL    | NULL    | NULL                                        | 1715 | Using where; Using temporary; Using filesort |
  17. |  1 | SIMPLE      | wpostmeta             | ref    | post_id          | post_id | 8       | blog.wposts.ID                              |   11 | Using index; Distinct                        |
  18. |  1 | SIMPLE      | wp_term_relationships | ref    | PRIMARY          | PRIMARY | 8       | blog.wposts.ID                              |   19 | Using index; Distinct                        |
  19. |  1 | SIMPLE      | wp_term_taxonomy      | eq_ref | PRIMARY          | PRIMARY | 8       | blog.wp_term_relationships.term_taxonomy_id |    1 | Using where; Distinct                        |
  20. +—-+————-+———————–+——–+——————+———+———+———————————————+——+———————————————-+
  21. 4 rows in set (0.02 sec)
  23. mysql>



  1. mysql> show create table wp_posts;
  2. +———-+————————–+
  3. | Table    | Create Table                                                                                                                                                                                                                                                                                                                                                                                                                                 |
  4. +———-+————————–+
  5. | wp_posts | CREATE TABLE `wp_posts` (
  6.   `ID` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
  7.   `post_author` bigint(20) unsigned NOT NULL DEFAULT '0',
  8.   `post_date` datetime NOT NULL DEFAULT '0000-00-00 00:00:00',
  9.   `post_date_gmt` datetime NOT NULL DEFAULT '0000-00-00 00:00:00',
  10.   `post_content` longtext NOT NULL,
  11.   `post_title` text NOT NULL,
  12.   `post_excerpt` text NOT NULL,
  13.   `post_status` varchar(20) NOT NULL DEFAULT 'publish',
  14.   `comment_status` varchar(20) NOT NULL DEFAULT 'open',
  15.   `ping_status` varchar(20) NOT NULL DEFAULT 'open',
  16.   `post_password` varchar(20) NOT NULL DEFAULT '',
  17.   `post_name` varchar(200) NOT NULL DEFAULT '',
  18.   `to_ping` text NOT NULL,
  19.   `pinged` text NOT NULL,
  20.   `post_modified` datetime NOT NULL DEFAULT '0000-00-00 00:00:00',
  21.   `post_modified_gmt` datetime NOT NULL DEFAULT '0000-00-00 00:00:00',
  22.   `post_content_filtered` longtext NOT NULL,
  23.   `post_parent` bigint(20) unsigned NOT NULL DEFAULT '0',
  24.   `guid` varchar(255) NOT NULL DEFAULT '',
  25.   `menu_order` int(11) NOT NULL DEFAULT '0',
  26.   `post_type` varchar(20) NOT NULL DEFAULT 'post',
  27.   `post_mime_type` varchar(100) NOT NULL DEFAULT '',
  28.   `comment_count` bigint(20) NOT NULL DEFAULT '0',
  29.   PRIMARY KEY (`ID`),
  30.   KEY `post_name` (`post_name`),
  31.   KEY `type_status_date` (`post_type`,`post_status`,`post_date`,`ID`),
  32.   KEY `post_parent` (`post_parent`),
  33.   KEY `post_author` (`post_author`),
  34.   FULLTEXT KEY `post_related` (`post_title`,`post_content`)
  36. +———-+———————-+
  37. 1 row in set (0.00 sec)
  39. mysql>

By the way above output is a paste from the the new PasteBin Open Source (Stikked powered) service I started on – ( 🙂

Before I took final decision to disable slow WP plugins, I've experimented a bit trying to add INDEX to Table Column (wposts) in hope that this would speed up SQL queries with:




But this didn't improve query speed even on the contrary it make execution time worse.

3. Tracking WordPress Plugin PHP Code Execution time and Plugins causing Slow SQL Queries (MySQL bottleneck) issues through WP itself

Well fine, I'm running my own hosted Blog and WordPress sites, but for people who have wordpress sites on shared hosting, there is usually no SSH (Terminal) Access to server, those people will be happy to hear there are 2 Free easy installable WordPress plugins which can be used to Debug Slow WordPress Plugins SQL Queries as well as plugin to Track which plugin takes most time to execute, this are:


a) P3 Plugin Performance Profiler  

runs a scan over your site to determine what resources your plugins are using, and when, during a standard page request. P3 PPP Can even create reports in a beatiful Excel like Pie chart sheet.


Another useful thing to see with P3 PPP is Detailed Timeline it shows when the plugins are being loaded during new page request so you can see if there is a certain sequence in time when a plugin slows down the website.


The pictures says it all as P3 PPP is Godaddy's work, congrats to GoDaddy, they've done great job.


b) WordPress memory Viewer WP plugins

Is useful to check how much memory each of WordPress plugin is taking on user (visitor) request.
Memory Viewer is allows you to view WordPress’ memory utilization at several hooks during WordPress’ execution. It also shows a summary of MySQL Queries that have ran as well as CPU time.
To use it download it to plugins/ folder as usual enable it from:

Installed Plugins -> (Inactive) -> Memory Viewer (Enable)

To see statistics from Memory Viewer open any post from your blog website and scroll down to the bottom you will notice the statistics, showing up there, like on below screenshot.


Though WP Memory Viewer is said to work only up to WP version 3.2.1, I've tested it and it works fine on my latest stable WordPress 4.1 based blog.

c) WordPress Query Monitor


Query Monitor is a debugging plugin for anyone developing with WordPress but also very helpful for anyone who want to track issues with plugins who use the database unefficient.
It has some advanced features not available in other debugging plugins, including automatic AJAX debugging and the ability to narrow down things by plugin or theme.
You can view plenty of precious statistics on how enabled plugins query the database server, here is a short overview on its Database Queries capabilities:

  • Shows all database queries performed on the current page
  • Shows affected rows and time for all queries
  • Show notifications for slow queries and queries with errors
  • Filter queries by query type (SELECT, UPDATE, DELETE, etc)
  • Filter queries by component (WordPress core, Plugin X, Plugin Y, theme)
  • Filter queries by calling function
  • View aggregate query information grouped by component, calling function, and type
  • Super advanced: Supports multiple instances of wpdb on one page
  • Once enabled from Plugins you will see it appear as a new menu on bottom Admin raw.

An important note to make here is latest Query Monitor extension fails when loaded on current latest Wordpress 4.1, to use it you will have to download and useolder Query Monitor plugin version 2.6.8 you can download it from here

d) Debug Bar

If you want you want a Memory Viewer like plugin for more complex used components memory debugging, reporting if (WP_DEBUG is set in wp-config.php) also check out Debug Bar .
For me Debug Bar was very useful because it show me depreciated functions some plugins used, so I substituted the obsoleted function with new one.



4. Server Hardware hungry (slow) WordPress plugins that you better not use

While spending time to Google for some fixes to WP slow query plugins – I've stumbled upon this post giving a good list with WordPress Plugins better off not to use because they will slow down your site
This is a publicly well known list of WP plugins every WordPress based site adminstrator should avoid, but until today I didn't know so my assumption is you don't know either ..

Below plugins are extremely database intensive mentioned in article that we should better (in all cases!) avoid:

  • Dynamic Related Posts
  • SEO Auto Links & Related Posts
  • Yet Another Related Posts Plugin
  • Similar Posts
  • Contextual Related Posts
  • Broken Link Checker — Overwhelms even our robust caching layer with an inordinate amount of HTTP requests.
  • MyReviewPlugin — Slams the database with a fairly significant amount of writes.
  • LinkMan — Much like the MyReviewPlugin above, LinkMan utilizes an unscalable amount of database writes.
  • Fuzzy SEO Booster — Causes MySQL issues as a site becomes more popular.
  • WP PostViews — Inefficiently writes to the database on every page load. To track traffic in a more scalable manner, both the stats module in Automattic’s Jetpack plugin and Google Analytics work wonderfully.
  • Tweet Blender — Does not play nicely with our caching layer and can cause increased server load.

A good Complete list of known WordPress slow plugins that will hammer down your wordpress performance is here

There are few alternatives to this plugins and when I have some free time I will download and test their alternatives but for now I plan the plugins to stay disabled.

For the absolute WP Performance Optimization Freaks, its good to check out the native way to Debug a wordpress installation through using few embedded


define('WP_DEBUG', true);
define('WP_DEBUG', false);
define('WP_DEBUG_LOG', true);
define('WP_DEBUG_DISPLAY', false);
define('SAVEQUERIES', true);


An article describing how you can use native WP debug variables is here

Happy Optimizing  ! 🙂

How to query LDAP (Windows Domain Controller) directory entries from Linux – ldapsearch common searche examples

Tuesday, November 18th, 2014

If you have a hybrid network of Windows servers and computers in Active Directory (AD) Domain Names and Linux hosts hosting various Java / PHP / Python applications like many of the middle and big companies (organization) have, sooner or later you will have to deploy an application which uses some some user authentication from the Linux host to Windows Domain Controller, you will end up in need to be able to query the AD, which is using LDAP (Lightweight Directory Access Protocol) to store the AD user credentials and tons of other information important for proper Active Directory operations.

LDAP is a key industry standard for storing and accessing distributed directory information services over Internet Protocol (IP). LDAP is great for sharing of information about users, systems, networks, services, and applications throughout the network. The corporate world nowadays would have been impossible without LDAP.
As of time of writting latest RFC  (Resource for Comment) 4511 document describes industrial specification of LDAP version 3.0 and therefore this is the most often used and implemented version.

LDAP protocol supports generally following operations:

Adding, Delete, Bind (Authenticate to LDAP server), Delete Search and Compare, Modify and Modify DN (Distringuished Name)
Deleting recordsh

On Linux to retrieve / locate AD entries, there is ldapsearch  command which opens connection to LDAP host server port, with set username and password. ldapsearch tool makes its search based on a filter.

To have make and modify queries in LDAP from GNU / Linux you will have to have installed ldap-utils on Debian, i.e.:

apt-get –yes install ldap-utils

to have ldapseach, ldapmodify, ldapsearch ldappasswd on CentOS / Redhat Linux, you need openldap-clients.x86_64

yum -y install openldap-clients.x86_64

Returned result from ldapsearch clients will be returned in LDIF format (LDAP Data Interchange format).

ldapsearch basic format is like thsi:

ldapsearch [optional_options] [optional_search_filter] [optional_list_of_attributes]

ldapsearch could query (LDAP – ADs) in unencrypted form simple LDAP, encrypted form with SSL certificate (LDAPs) or through LDAP with STARTTLS.
Logically most organizations nowadays are using LDAPs, as it offers the highest level of security. Unencrypted LDAP servers listen usually on
port 389, LDAPs communicates on port 636 once an SSL handshake is made between client and server and LDAP with STARTTLS communicates on standard port 389.

Here is 3 examples of common  ldapsearch queries

1. Return all entries in LDAP server

ldapsearch -D "cn=directory manager" -w secret -p 389 -h -b "dc=your-organization,dc=com" -s sub "(objectclass=*)"

"objectclass=*" is a serch filter matching all entries in the directory (time and size limits on output limit set for the server will take affect)

2. Searching the Root DSE Entry

root DSE is special entry containing list of all suffixes supported by local Directory Server. Getting root DSE is done with  base of "", a search scope of base, and a filter of "objectclass=*"

ldapsearch -D "cn=directory manager" -w secret_pass -p 389 -h  -b "dc=your-organization,dc=com" -s sub "cn=babs jensen"


3. Searching Directory Server Schema Entry

LDAP server stores all directory server schema in special entry cn=schema.
schema entry contains information on every object class and attribute defined for the Directory Server. Command to searches  contents of the cn=schema entry is:

ldapsearch -D "cn=directory manager" -w secret_pass -p 389 -h -b "cn=schema" -s base "objectclass=*"

4. Check whether cn=My-Account1 account is working and enabled

ldapsearch -H ldaps:// -b o=my-org,c=bg -s sub -D cn=My-Account1,ou=users,ou=ABC,o=my-org,c=ABC -W '(&(cn=My-Acount1)(objectclass=my-org-Account))'

5. check all members of cn=MY_ADMINISTRATION


ldapsearch -H ldaps:// -b o=my-org,c=bg -s sub -D cn=My-Account1,ou=users,ou=ABC,o=my-org,c=ABC -W '(&(cn=MY_ADMINISTRATION)(member=*))'


6. check all members of all groups belonging to user

ldapsearch -H ldaps:// -b ou=ABC,ou=ABC1,ou=ABC2,ou=groups,ou=ABC,o=my-org,c=ABC -s sub -D cn=My-Account1,ou=users,ou=ABC,o=my-org,c=ABC -W '(cn=*)'

Whether ldapsearch queries are to be common and scripted or just for simplification of readability of query to LDAP it is useful to use LDAP_BASEDN – a query search base. By setting search base you can further omit in query -b

export LDAP_BASEDN="dc=your-organization,dc=com"
ldapsearch -D "cn=directory manager" -w secret_pass -p 389 -h "cn=labs jordan"

In Linux LDAP's open-source implementation is called OpenLDAP.
On Linux LDAP protocol can be easily integrated / used in combination with FTP servers (such as proftpd), DNS servers, Mail Servers (Courier), Samba servers, Radius (IP Telephony), sudo, as well as most programming languages such as PHP, Python etc.

Oracle: Get database, tables and instances access permissions

Thursday, January 30th, 2014

Oracle user get permissions of table database and instances access
If you are logged in to Oracle SQL server with sqlplus and you're not sure to which Database, Tables, Object instances you have permissions to below 2 queries will be of use:


Query lists all queries in a Oracle table schema. Alternavite shorter way to do the query is via:

SQL> SELECT table_name FROM user_tables;


Shows your own schema's all tables and views.

Other oracle useful query is the Oracle equivalent of MySQL SHOW TABLES;

SQL> SELECT table_name FROM user_tables;

It will also output info only for logged in user credentials, if you're logged in as oracle database administrator (DBA role) account and you would like to check what Instances are owned by any user lets say user GEORGI query should be;


Other way to do it is via:

SQL> SELECT Table_Name from All_Tables WHERE OWNER = 'YOURSCHEMA';

MySQL SSL Configure Howto – How to Make MySQL communication secured

Wednesday, January 15th, 2014

mysql-over-ssl-how-to-configure-logo how to configure ssl on mysql server

Recently I've been asked How to make communication to MySQL database encrypted. The question was raised by a fellow developer who works on developing a Desktop standalone application in Delphi Programming Language with DevArt an (SQL Connection Component capable to connect Delphi applications to multiple databases like MySQL, Oracle, PostgreSQL, Interbase, Firebird etc.

Communicating in Secured form to MySQL database is not common task to do, as MySQL usually communicates to applications hosted on same server or applications to communicate to MySQL are in secured DMZ or administrated via phpMyAdmin web interface.

MySQL supports encrypted connections to itself using Secure Socket Layer (SSL) encryption. Setting up MySQL db to be communicated encrypted is a must for standalone Desktop applications which has to extract / insert data via remote SQL.
Configuring SQL to support communicated queries encrpytion is supported by default and easily configured on most standard Linux version distributions (Debian, RHEL, Fedora) with no need to recompile it.
1. Generate SSL Certificates

$ mkdir /etc/mysql-ssl && cd mysql-ssl

# Create CA certificate
$ openssl genrsa 2048 > ca-key.pem
$ openssl req -new -x509 -nodes -days 3600 \
         -key ca-key.pem -out ca-cert.pem

Create server certificate, remove passphrase, and sign it
server-cert.pem is public key, server-key.pem is private key
$ openssl req -newkey rsa:2048 -days 3600 \
         -nodes -keyout server-key.pem -out server-req.pem

$ openssl rsa -in server-key.pem -out server-key.pem
$ openssl x509 -req -in server-req.pem -days 3600 \
         -CA ca-cert.pem -CAkey ca-key.pem -set_serial 01 -out server-cert.pem

Create client certificate, remove passphrase, and sign it
client-cert.pem is public key and client-key.pem is private key
$ openssl req -newkey rsa:2048 -days 3600 \
         -nodes -keyout client-key.pem -out client-req.pem

$ openssl rsa -in client-key.pem -out client-key.pem
$ openssl x509 -req -in client-req.pem -days 3600 \
         -CA ca-cert.pem -CAkey ca-key.pem -set_serial 01 -out client-cert.pem

After generating the certificates, verify them:

$ openssl verify -CAfile ca-cert.pem server-cert.pem client-cert.pem

2. Add SSL support variables to my.cnf

Once SSL key pair files are generated in order to active SSL encryption support in MySQL server, add to (/etc/my.cnf,  /etc/mysql/my.cnf, /usr/local/etc/my.cnf … ) or wherever config is depending on distro


3. Restart MySQL server

/etc/init.d/mysqld restart

4. Create SQL user to require SSL login

Create new user with access to database;

GRANT ALL ON Sql_User_DB.* TO Sql_User@localhost;

To create administrator privileges user:


5. Test SSL Connection with MySQL CLI client or with few lines of PHP

To use mysql cli for testing whether SSL connection works:

$ mysql -u ssluser -p'pass' –ssl-ca /etc/mysql-ssl/client-cert.pem –ssl-cert /etc/mysql-ssl/client-key.pem

Once connected to MySQL to verify SSL connection works fine:

mysql> SHOW STATUS LIKE 'Ssl_Cipher';
| Variable_name | Value              |
| Ssl_cipher    | DHE-RSA-AES256-SHA |

If you get this output this means MySQL SSL Connection is working as should.

Alternative way is to use test-mysqli-ssl.php script to test availability to mysql over SSL.

mysqli_ssl_set($conn, '/etc/mysql-ssl/client-key.pem', '/etc/mysql-ssl/client-cert.pem', NULL, NULL, NULL);
if (!mysqli_real_connect($conn, '', 'ssluser', 'pass')) { die(); }
$res = mysqli_query($conn, 'SHOW STATUS like "Ssl_cipher"');

Note: Change username password according to your user / pass before using the script

That's all now you have mysql communicating queries data over SSL


How to disable tidy HTML corrector and validator to output error and warning messages

Sunday, March 18th, 2012

I've noticed in /var/log/apache2/error.log on one of the Debian servers I manage a lot of warnings and errors produced by tidy HTML syntax checker and reformatter program.

There were actually quite plenty frequently appearing messages in the the log like:

To learn more about HTML Tidy see
Please fill bug reports and queries using the "tracker" on the Tidy web site.
Additionally, questions can be sent to
HTML and CSS specifications are available from
Lobby your company to join W3C, see
line 1 column 1 - Warning: missing <!DOCTYPE> declaration
line 1 column 1 - Warning: plain text isn't allowed in <head> elements
line 1 column 1 - Info: <head> previously mentioned
line 1 column 1 - Warning: inserting implicit <body>
line 1 column 1 - Warning: inserting missing 'title' element
Info: Document content looks like HTML 3.2
4 warnings, 0 errors were found!

I did a quick investigation on where from this messages are logged in error.log, and discovered few .php scripts in one of the websites containing the tidy string.
I used Linux find + grep cmds find in all php files the "tidy "string, like so:

server:~# find . -iname '*.php'-exec grep -rli 'tidy' '{}' ;
find . -iname '*.php' -exec grep -rli 'tidy' '{}' ; ./new_design/modules/index.mod.php

Opening the files, with vim to check about how tidy is invoked, revealed tidy calls like:

exec('/usr/bin/tidy -e -ashtml -utf8 '.$tmp_name,$rett);

As you see the PHP programmers who wrote this website, made a bigtidy mess. Instead of using php5's tidy module, they hard coded tidy external command to be invoked via php's exec(); external tidy command invocation.
This is extremely bad practice, since it spawns the command via a pseudo limited apache shell.
I've notified about the issue, but I don't know when, the external tidy calls will be rewritten.

Until the external tidy invocations are rewritten to use the php tidy module, I decided to at least remove the tidy warnings and errors output.

To remove the warning and error messages I've changed:

exec('/usr/bin/tidy -e -ashtml -utf8 '.$tmp_name,$rett);

exec('/usr/bin/tidy --show-warnings no --show-errors no -q -e -ashtml -utf8 '.$tmp_name,$rett);

The extra switches meaning is like so:

q – instructs tidy to produce quiet output
-e – show only errors and warnings
–show warnings no && –show errors no, completely disable warnings and error output

Onwards tidy no longer logs junk messages in error.log Not logging all this useless warnings and errors has positive effect on overall server performance especially, when the scripts, running /usr/bin/tidy are called as frequently as 1000 times per sec. or more

Possible way to Improve wordpress performance with wp-config.php 4 config variables

Tuesday, March 6th, 2012

Wordpress improve performance wp-config.php logo chromium effect GIMP

Nowdays WordPress is ran by million of blogs and websites all around the net. I myself run wordpress for this blog in general wordpress behaves quite well in terms of performance. However as with time the visitors tend to increase, on frequently updated websites or blogs. As a consequence, the blog / website performance slowly starts to decrease as result of the MySQL server read / write operations creating I/O and CPU load overheads. Buying a new hardware and migrating the wordpress database is a possible solution, however for many small or middle size wordpress blogs en sites like mine this is not easy task. Getting a dedicated server or simply upgrading your home server hardware is expensive and time consuming process… In my efforts to maximize my hardware utilization and increase my blog decaying performance I've stumbled on the article Optimize WordPress performance with wp-config.php

According to the article there are 4 simple wp-config.php config directvies useful in decreasing a lot of queries to the MySQL server issued with each blog visitor.

define('TEMPLATEPATH', '/var/www/blog/wp-content/themes/default');
define('STYLESHEETPATH', '/var/www/blog/wp-content/themes/default');

1. WP_HOME and WP_SITEURL wp-config.php directvies

The WP_HOME and WP_SITEURL variables are used to hard-code the address of the wordpress blog or site url, so wordpress doesn't have to check everytime in the database on every user request to know it is own URL address.


This variables will surely improve performance to Wodpress blogs which doesn't implement caching. On wp install with enabled caching plugins like WordPress Super Cache, Hyper Cache or WordPress Db Cache is used, I don't know if this variables will have performance impact …

So far I have tested the vars on a couple of wordpress based installs with caching enabled and even on them it seems the pages load faster than before, but I cannot say this for sure as I did not check the site loading time in advance before hardcoding the vars.

Anyways even if the suggested variables couldn't make positive impact on performance, having the four variables in wp-config.php is a good practice for blogs or websites which are looking for extra clarity.
For multiple wordpress installations living on the same server, having defined the 4 vars in different wordpress seems like a good idea too.

Two wordpress plugins to accelerate wordpress opening times and decrease server load time

Thursday, September 22nd, 2011

A Comparison of wordpress webpage responce with and without wp dbcache

A combination of two wordpress caching plugins (Hyper Cache and Db Cachesignificantly improves the access times of a wordpress based blogs and websites.

Installing the two websites has drastically improved my blog opening times, so in my view having the two plugins on every wordpress install out there is a must! 🙂
The plugins installation is straight forward, here is how I installed them.

1. Installing Hyper Cache on WordPress

To install Hyper Cache all I had to do is download and enable the plugin, the plugin doesn’t require any configuration. I always love it when I don’t have to bother with reading configuration options and pondering for some 20 minutes on the plugin features, so in that perspective Hyper Cache in my view is a good alternative to WordPress Super Cache

Besides that WordPress Super Cache was having issues when enabled on few wordpress based websites I manage these days. For comparison Hyper Cache worked just great on all wordpress install I tried the plugin so far.

To install all I had to do is download the plugin unzip and enable it:

a. Download and unzip it

debian:/var/www/blog# wget
debian:/var/www/blog# cd wp-content/plugins
debian:/var/www/blog/wp-content/plugins# unzip

b. Enable Hyper Cache plugin

To enable the plugin follow to standard plugin location;

Plugins -> Inactive -> Hyper Cache (Enable)

To enable the plugin follow to standard plugin location;

Plugins -> Inactive -> Hyper Cache (Enable)


A  mirror of current version of plugin is here 

2. Installing Wodpress Db Cache

What Db Cache, does it does caching of last queries made to MySQL for specified time, so if the query has to be refetched again from wordpress’s php frontend the queries results are fetched straight for the memory. This decreases the load towards the MySQL server and increases the webpages loading time.

As the plugin page suggests it’s way faster than other html caching-plugins like WP-Cache  or WP Super Cache

However, I think its still slower than using a combination of WP Super Cache’s alternative Hyper Cache  and  Db Cache . Combining this two could rise the webpage opening times according to some statisticonline at best cases up to 830% !! 😉 Let me proceed with how I did the install of  Db Cache .

a. Download and Install Db Cache


debian:/var/www/blog/wp-content/plugins# wget


debian:/var/www/blog/wp-content/plugins# unzip


b. Enable the plugin 


Plugins -> Inactive -> Db Cache (Enable)


c. Make sure the permissions for Db Cache are correct

On Debian to enable Db Cache, the permissions should be changed for Apache to have a read/write permissions to plugin directory, on Debian to fix the permissions I used the commands:

debian:/var/www/blog# chown www-data:www-data wp-content

debian:/var/www/blog# chown -R www-data:www-data wp-content/plugins/db-cache

On other GNU/Linux distributions the above commands (user and group) www-data:www-data, should be set to whatever user/group Apache is running with, on Slackware this would be nobody:nobody, on CentOS and RHEL it would be apache:apache.

Finally to enable Db Cache go to

Settings -> Db Cache -> (Tick Enable) -> Save

I’ve also made a mirror of Db Cache plugin here

Enjoy the speed boost 😉

How to list and exclude table names from a database in MySQL (exclude table names from an show tables in MySQL) by using information_schema

Wednesday, March 30th, 2011

Listing all table names from a MySQL database is a very easy and trivial task that every sql or system administrator out there is aware of.

However excluding certain table names from a whole list of tables belonging to a database is not that commonly used and therefore I believe many people have no clue how to do it when they have to.

Today for one of my sql backup scripts it was necessary that certain tables from a database to be excluded from the whole list of tables for a database I’m backupping.
My example database has the sample name exampledatabase and usually I do list all the table contents from that database with the well known command:

mysql> SHOW tables from exampledatabase;

However as my desire was to exclude certain tables from the list (preferrably with a certain SQL query) I had to ask around in for some hints on a ways to achieve my exclude table goals.

I was adviced by some people in #mysql that what I need to achieve my goal is the information_schema mysql structure, which is available since MySQL version 5.0.

After a bit of look around in the information_schema and the respective documentation on, thanksfully I could comprehend the idea behind the information_schema, though to be honest the first time I saw the documentation it was completly foggy on how to use this information_schema;
It seems using the information_schema is very easy and is not much different from your normal queries syntax used to do trivial operations in the mysql server.

If you wonder just like I did what is mysql’s information_schema go and use the information_schema database (which I believe is a virtual database that is stored in the system memory).

For instance:

mysql> use information_schema;
Database changed
mysql> show tables
| Tables_in_information_schema |
17 rows in set (0.00 sec)

To get a general view on what each of the tables in the information_schema database contains I used the normal SELECT command for example

mysql> select * from TABLES limit 10;

I used the limit clause in order to prevent being overfilled with data, where I could still see the table fields name to get general and few lines of the table to get an idea what kind of information the TABLES table contains.

If you haven’t got any ecperience with using the information_schema I would advice you do follow my example select and look around through all the listed tables in the information_schema database

That will also give you a few hints about the exact way the MySQL works and comprehends it’s contained data structures.

In short information_schema virtual database and it’s existing tables provides a very thorough information and if you’re an SQL admin you certainly want to look over it every now and then.

A bit of playing with it lead me to a command which is actually a good substitute for the normal SHOW TABLES; mysql command.
To achieve a SHOW TABLES from exampledatabase via the information_schema info structure you can for example issue:

select TABLE_NAME from TABLES where TABLE_SCHEMA='exampledatabase';

Now as I’ve said a few words about information_schema let me go back to the main topic of this small article, which is How to exclude table names from a SHOW tables list

Here is how exclude a number of tables from a complete list of tables belonging to a database:

select TABLE_NAME from TABLES where TABLE_SCHEMA='exampledatabase'
('mysql_table1_to_exlude_from_list', 'mysql_table2_to_exclude_from_list', 'table3_to_exclude');

In this example the above mysql command will list all the tables content belonging to exampledatabase and instruct the MySQL server not to list the table names with names mysql_table1_to_exlude_from_list, mysql_table2_to_exclude_from_list, table3_to_exclude

If you need to exclude more tables from your mysql table listing just add some more tables after the …’table3_to_exclude’, ‘new_table4_to_exclude’,’etc..’);

Of course this example can easily be adopted to a MySQL backup script which requires the exclusion of certain tables from a backed up database.

An example on how you can use the above table exclude command straight from the bash shell would be:

debian:~# echo "use information_schema; select TABLE_NAME from TABLES where
TABLE_SCHEMA='exampledatabase' AND TABLE_NAME not in
('mysql_table1_to_exlude_from_list', 'mysql_table2_to_exclude_from_list', 'table3_to_exclude',);"
| mysql -u root -p

Now this little bash one-liner can easily be customized to a backup script to create backups of a certain databases with a certain tables (e.g. with excluded number of tables) from the backup.

It’s seriously a pity that by default the mysqldump command does not have an option for a certain tables exclude while making a database dump.
I’ve saw the mysqldump exclude option, being suggested somewhere online as a future feature of mysqldump, I’ve also seen it being reported in the’s bug database, I truly hope in the upcoming releases we will see the exclude option to appear as a possible mysqldump argument.