I’d be glad to read your last post concerning the detection in URLs.

Keep-up the good work

Do you really use to ability to use the same text for different fields? That is, e.g. having the same id in the addons.description and addons.eula columns? That would seem to me to be the only reason for having the addons.description and addons.eula columns at all (and if you really didn’t want the database to be able to use an index — since the optimizer can’t know if the id’s used will be consecutive or scattered).

Otherwise you could instead have had:
create table translations2 (
id int(11) unsigned,
field varchar(20),
locale varchar(10),
value text NULL,
created datetime NULL,
modified datetime NULL,
primary key (id, locale, field)
);
For performance you would probably have an covering index on (id, field, locale, value) to make sure you could get to the data in one go.

For having more than one fallback locale, you might have a table translationfallback:
create table translationfallback (
locale varchar(10),
fallback varchar(10),
sort int unsigned NOT NULL,
primary key (locale, fallback)
);
The table should always have a row with locale=fallback and sort=0 for each locale to make it the most preferred, and a row with fallback=’default’ and sort=1000 for each locale to make sql easier.

As for the sql itself, you might want to eliminate some of the join:
SELECT a.id, a.guid,
SUBSTR(MIN(IF(t.field=’name’,LPAD(tfb.sort,10,’0′)+t.value)),11) AS name,
a.defaultlocale, a.addontype_id, a.status, a.icontype,
SUBSTR(MIN(IF(t.field=’homepage’,LPAD(tfb.sort,10,’0′)+t.value)),11) AS homepage,
SUBSTR(MIN(IF(t.field=’description’,LPAD(tfb.sort,10,’0′)+t.value)),11) AS description,
SUBSTR(MIN(IF(t.field=’summary’,LPAD(tfb.sort,10,’0′)+t.value)),11) AS summary,
a.averagerating, a.weeklydownloads, a.totaldownloads,
SUBSTR(MIN(IF(t.field=’developercomments’,LPAD(tfb.sort,10,’0′)+t.value)),11) AS developercomments,
a.inactive, a.trusted, a.viewsource, a.prerelease, a.adminreview, a.sitespecific, a.externalsoftware,
SUBSTR(MIN(IF(t.field=’eula’,LPAD(tfb.sort,10,’0′)+t.value)),11) AS eula,
SUBSTR(MIN(IF(t.field=’privacypolicy’,LPAD(tfb.sort,10,’0′)+t.value)),11) AS privacypolicy,
a.created, a.modified,
SUBSTR(MIN(IF(t.field=’description’,LPAD(tfb.sort,10,’0′)+t.locale)),11) AS description _locale,
SUBSTR(MIN(IF(t.field=’developercomments’,LPAD(tfb.sort,10,’0′)+t.locale)),11) AS developercomments,
SUBSTR(MIN(IF(t.field=’eula’,LPAD(tfb.sort,10,’0′)+t.locale)),11) AS eula,
SUBSTR(MIN(IF(t.field=’homepage’,LPAD(tfb.sort,10,’0′)+t.locale)),11) AS homepage,
SUBSTR(MIN(IF(t.field=’name’,LPAD(tfb.sort,10,’0′)+t.locale)),11) AS name,
SUBSTR(MIN(IF(t.field=’privacypolicy’,LPAD(tfb.sort,10,’0′)+t.locale)),11) AS privacypolicy,
SUBSTR(MIN(IF(t.field=’summary’,LPAD(tfb.sort,10,’0′)+t.locale)),11) AS summary
FROM addons AS a
INNER JOIN addontypes AS aot ON a.addontype_id=aot.id
LEFT JOIN (translationfallback AS tfb
INNER JOIN translations AS t ON a.description=t.id AND t.locale=if(tfb.fallback=’default’, a.defaultlocale, tfb.fallback)
) ON tfb.locale=’en-US’
WHERE (a.id = 9) AND (a.inactive = 0) AND (a.addontype_id IN (1, 2))
GROUP BY a.id, a.guid, a.defaultlocale, a.addontype_id, a.status,
a.icontype, a.averagerating, a.weeklydownloads, a.totaldownloads, a.inactive,
a.trusted, a.viewsource, a.prerelease, a.adminreview, a.sitespecific,
a.externalsoftware, a.created, a.modified

But, really, it seems kind of silly to use the old “database-in-a-database” pattern where you have a table of entities and a table with its attributes, instead of just two tables:
create table moz_addons (
id int unsigned,
guid varchar(16),
defaultlocale varchar(10) not null,
addontype_id int unsigned not null,
status int unsigned not null,
icontype int unsigned not null,
averagerating int unsigned not null,
weeklydownloads int unsigned not null,
totaldownloads int unsigned not null,
inactive int unsigned not null,
trusted int unsigned not null,
viewsource int unsigned not null,
prerelease int unsigned not null,
adminreview int unsigned not null,
sitespecific int unsigned not null,
externalsoftware int unsigned not null,
created datetime not null,
modified datetime not null,
primary key (id),
foreign key (addontype_id) references moz_addontype (id),
);

create table addontranslations (
id int unsigned,
locale varchar(10),
name text null,
homepage text null,
description text null,
summary text null,
developercomments text null,
eula text null,
privacypolicy text null,
primary key (id, locale),
foreign key (id) references addons (id),
);