When SHOW WARNINGS after EXPLAIN EXTENDED shows
Note 1276 The field or link "test.foo.bar" for SELECT # 2 was enabled in SELECT # 1
what exactly does this mean and what effect does it have? In my case, this prevents mysql from using what seems like a perfectly good index. But this is not about fixing this particular request (since this is an irrelevant test).
I found http://dev.mysql.com/doc/refman/5.0/en/error-messages-server.html , but
Error: 1276 SQLSTATE: HY000 (ER_WARN_FIELD_RESOLVED)
Message: Field or reference '% s% s% s% s% s' of SELECT #% d was resolved in SELECT #% d
doesn't really explain.
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