tag:blogger.com,1999:blog-5124641802818980374.post1878760489083684070..comments2023-09-06T11:58:30.752+02:00Comments on Oracle related stuff: When your projection is not cost-freeUnknownnoreply@blogger.comBlogger2125tag:blogger.com,1999:blog-5124641802818980374.post-43912124276739507492010-03-18T17:38:51.265+01:002010-03-18T17:38:51.265+01:00Mark,
if you are referring to the "no_place_...Mark,<br /><br />if you are referring to the "no_place_group_by" hint, then yes, I think this does the same and effectively disables this optimization. There are certain bugs in 11.1 that you might hit and therefore support might suggest this setting.<br /><br />It will affect the performance in those cases where you currently benefit from the new optimization - there is no way to tell how much impact this will have on your performance without further analysis.<br /><br />If your system was already running on 10g, then your SQLs were already running without that optimization since it was introduced in 11.1 - may be this can give you a clue about the impact, but it is not necessarily a fair comparison since you might benefit from other optimizer changes introduced in 11.1.<br /><br />For more information about that optimization, you can e.g. read the <a href="http://jonathanlewis.wordpress.com/2008/12/21/group-by/" rel="nofollow">blog post</a> by Jonathan Lewis.<br /><br />RandolfRandolfhttps://www.blogger.com/profile/13463198440639982695noreply@blogger.comtag:blogger.com,1999:blog-5124641802818980374.post-33722104627446300002010-03-18T16:26:14.839+01:002010-03-18T16:26:14.839+01:00Oracle is stating that we set "_optimizer_gro...Oracle is stating that we set "_optimizer_group_by_placement" = FALSE - Does this do the same thing as the hint in the post? Any idea how this will affect performance?<br /><br />Mark WoodUnknownhttps://www.blogger.com/profile/11464884333453797229noreply@blogger.com