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);