1--- add language column (work around alter table not working with primary key) 2 3DROP INDEX idx_pid; 4 5CREATE TABLE taggings_tmp (pid, tag, tagger, PRIMARY KEY(pid, tag, tagger)); 6INSERT INTO taggings_tmp SELECT pid, tag, tagger FROM taggings; 7DROP TABLE taggings; 8 9 10CREATE TABLE taggings (pid, tag, tagger, lang, PRIMARY KEY(pid, tag, tagger)); 11INSERT INTO taggings SELECT pid, tag, tagger, '' FROM taggings_tmp; 12DROP TABLE taggings_tmp; 13 14CREATE INDEX idx_taggings_pid ON taggings(pid); 15CREATE INDEX idx_taggings_lang ON taggings(lang);