Re: [HACKERS] GEQO optimizer (was Re: Backend message type 0x44 arrived while idle)

Oleg Bartunov <oleg(at)sai(dot)msu(dot)su> writes:
> I confirm big join with 11 tables doesn't eats all memory+swap on
> my Linux box as before and it runs *forever* :-). It took already
> 18 minutes of CPU (P200, 64Mb) ! Will wait.

18 minutes??? It takes barely over a minute on my aging 75MHz HP-PA
box. (Practically all of which is planning time, since there are only
10 tuples to join... or are you doing this on a realistically sized
set of tables now?)

> This query doesn't use (expicitly) GEQO

> select t0.a,t1.a as t1,t2.a as t2,t3.a as t3,t4.a as t4,t5.a as t5,t6.a as t6,t7.a as t7,t8.a as t8,t9.a as t9,t10.a as t10
> from t0 ,t1,t2,t3,t4,t5,t6,t7,t8,t9,t10
> where t1.a_id = t0.a_t1_id and t2.a_id=t0.a_t2_id and t3.a_id=t0.a_t3_id and t4.a_id=t0.a_t4_id and t5.a_id=t0.a_t5_id and t6.a_id=t0.a_t6_id and t7.a_id=t0.a_t7_id and t8.a_id=t0.a_t8_id and t9.a_id=t0.a_t9_id and t10.a_id=t0.a_t10_id ;

No, but since there are 11 tables mentioned, it will be sent to the GEQO
optimizer anyway with the default GEQO threshold of 11...

regards, tom lane