MySQL explain plan cheat sheet

Explanation of explain output:

• select_type: SIMPLE/SUBQUERY/UNION/DERIVED
• partitions: NULL ??
• type: (from worst to the best): ALL, index, range, ref, eq_ref, const, system
• possible_keys: food,bar,baz,id (good)
• key: foo(good)
• key_len: 334 ??
• ref: const,const,const ??
• rows: 1 (lower is better. must be less than total rows)
• filtered: 100.00 (lower is better, but only used if there's a join)
• Extra: NULL

Bad extra values:

• using where
• using temporary
• using filesort

Good extra values:

• using index