mysql - Slow query with where,group by, order by (using filesort) -

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hi have trouble optimizing query. have reduced original query (~2 seconds) (0.3s):

select kunden.id, kunden.typ, cache.bestellungen_count  cache inner join kunden on kunden.id=cache.kunde_id kunden.kundentyp=1  group kunden.id   --  order kunden.id desc order cache.bestellungen_gesamtbetrag desc limit 0,500

explain shows filesort used.

select_type     table   type    possible_keys   key     key_len     ref     rows       simple  kunden  ref     primary,kundentyp,id_k...   kundentyp   4   const   26235   using where; using temporary; using filesort simple  cache   ref     kunde_id,kunde_id_gesamtbetrag  kunde_id    4   partyschnaps.kunden.indexh  1   using index condition

i guess problem where, group , order cannot use index, when order kunden.id performance boosts factor of ~30 (0.01s) , can solved index.

index on cache table order column , combined 1 fk kunden_id , order column have no effect.


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