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May 2009

Order of keys inside index blocks

In this post we are going to illustrate how index keys are ordered inside a leaf block of an Oracle B+tree index.

It is well known that index blocks share most of their structure with “regular” (heap) table blocks; in particular, they share most of the way entries are stored inside the block. In tables, a row can be placed anywhere in the bottom part of the block (which is essentially managed like an “heap”, in which the exact memory address that the row is stored at is not important); its row address is recorded into one of the slots of a vector named “row directory”, located near the beginning of the block.…

Why blogging ?

Mainly because I like to write, and people usually like my writings. So, why not ?

Also – because it is a good way of learning. When I was a student, I remember that my favorite reharsal technique was to pretend I was explaining the topic to an imaginary person that knew nothing about it – and that technique worked very well, because when explaining, I very frequently discovered flaws in my knowledge that prompted me to improve even more.…