CHAPTER 7Histograms
A lot of misinformation exists on the Internet about histograms: what they do, what they look like, how they work, and when they don't work. There are also plenty of gaps in the available information.
In this chapter, I hope to fill in some of those gaps and correct some of the misunderstandings. Unfortunately, I shall never know how successful I have been in this aim, because I recently came across bug 2757360 on MetaLink, dated Jan 2003, which included the wonderful line: "There are any number of bugs on the CBO and histogram behavior ..."
You could ask many questions about histograms, but the important ones are probably these: what are histograms; how does Oracle use them; when does Oracle use them; when does Oracle ignore ...
Get Cost-Based Oracle Fundamentals now with the O’Reilly learning platform.
O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.
