Debugging with the General Query Log
In the mysql console, you can use a global variable to turn logging on
SET global general_log = 1;
And specify the log file (The MySQL user must have write permission to this file.)
SET global general_log_file = '/var/log/mariadb/mariadb.log';
Then you can do some action that you want to examine the queries for, and TURN OFF the general query log immediately. A busy server will fill up all disk space with a huge log file if you don't turn it off.
SET global general_log = 0;
Query Examples
Some database queries that you might want to use and bookmark in your database administration tool such as MySQL Query Browser. http://dev.mysql.com/downloads/gui-tools/5.0.html or SQLyog http://www.webyog.com/en/index.php
-- what database schema do you want to use?
use wiki_demo;
-- What would a create database statement look like?
show create database wiki_demo;
-- How about a table?
show create table wiki_demo.l10n_cache;
# What character collations are specified for each table and column (that supersede any global declaration or default.)
SELECT
TABLE_SCHEMA, TABLE_NAME, COLUMN_NAME, COLLATION_NAME
FROM information_schema.columns AS cols
WHERE table_schema = 'wiki_demo';
Here is a query that will show you the pages in your wiki that contain a particular string. In this example, I wanted to find all pages that were using the 'Icon' extension parser extension magic word '#icon'.
SELECT DISTINCT
page_title
FROM
page
RIGHT JOIN
revision
ON page_id = rev_page
WHERE
rev_text_id
IN (
SELECT
old_id
FROM
text
WHERE
# old_text LIKE '%#icon%'
old_text REGEXP('#icon') # regex is easier to deal with
)
A more complex query that summarizes some information about an article (You supply the article title)
SELECT
p.page_id 'id',
p.page_title 'title',
p.page_namespace 'namespace',
t.old_id 'latest text id',
t.old_text 'content',
r.rev_id,
r.rev_comment 'comment',
r.rev_user,
r.rev_user_text,
r.rev_parent_id 'previous revision'
FROM
text t
RIGHT JOIN
revision r
ON t.old_id = r.rev_text_id
RIGHT JOIN
page p
ON r.rev_id = p.page_latest
WHERE
p.page_title = 'Main_Page'