Left join ignores optimizer directive

Posted in 2000

Topics: Performance & Tuning, SQL Development & Query Writing

Ross Berman — Wed, 10 May 2000 01:24:10 GMT — source: Informix-list mailing list archive (1991-1998)

Hey, I'm wondering if anyone out there has had difficulties with left joins? Our query goes incredibly slow with optimize set high and fairly quickly with it set low. In order to improve performance, we brought in a performance expert who specified some optimizer directives. With explain turned on, Informix (IDS9.20.UC2) says that it found and used the directives, only it didn't. The explain output shows that it did not follow the directives we specified. Anyone seen this before? -Ross rossberman@earthlink.net

↪ replying to Ross Berman

Erik Stahlhut — Wed, 10 May 2000 11:58:15 +0100 — source: Informix-list mailing list archive (1991-1998)

No, but I know from the Informix Technical Support that the 9.20 UC2 has a bug in the optimizer which should be fixed in 9.21. regards Erik Stahlhut Ross Berman schrieb in Nachricht <3918BAAD.D36432B@yahoo.com>... >Hey, I'm wondering if anyone out there has had difficulties with left >joins? Our query goes incredibly slow with optimize set high and fairly >quickly with it set low. In order to improve performance, we brought in >a performance expert who specified some optimizer directives. With >explain turned on, Informix (IDS9.20.UC2) says that it found and used >the directives, only it didn't. The explain output shows that it did >not follow the directives we specified. Anyone seen this before? > >-Ross > >rossberman@earthlink.net >