Comment 3 for bug 308913

Ahem. Slight omission in the example query above, of course: POTemplate.id = TranslationMessage.potemplate. So it becomes
{{{
UPDATE TranslationMessage
SET potemplate = NULL
FROM POTemplate
WHERE
    POTemplate.id = TranslationMessage.potemplate AND
    POTemplate.path LIKE '%.xpi' AND
    language = 119;
}}}

The update currently creates no duplicates and takes about a minute to run, updating 25K rows.