Hello,
  (google translate)

I am a little fun with the optimizer.

sql>select count (distinct idvisiteur) from src_inbox__at__lm__visites;
+ ---------- +
| L1 |
+ + ==========
| 75528080 |
+ ---------- +
1 tuple (3m 51s) 

sql>set optimizer = 'minimal_pipe; 

sql>select count (distinct idvisiteur) from src_inbox__at__lm__visites;
+ ---------- +
| L1 |
+ + ==========
| 75528080 |
+ ---------- +
1 tuple (1m 28s) 

sql>set optimizer = 'default_pipe; 

sql>select count (distinct idvisiteur) from src_inbox__at__lm__visites;
+ ---------- +
| L1 |
+ + ==========
| 75528080 |
+ ---------- +
1 tuple (3m 54s)

It's very interesting.
Is there a risk to change optimizer ? What are the best practices ?

thank you

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