One small query in relation between buckets and directories in extendible hashing.

[Vivek Nakum]

Hello Tutors,

In extendible hashing,

If global depth of directory is let me say 4, and there is a directory with id 1001. Now suppose there is a bucket A of local depth 3 with id 001. So, will this directory id 1001 point to this bucket?

While pointing to a directory to a bucket, should we see the last d' bits of directory or should we see the first d' bits of directory where d' is a local depth.

If we see the first d' bits of directory id, then the directories which will point to this bucket are 0010 and 0011. If we see the last d' bits, then the directories which will poin to this bucket are 0001 and 1001. 

So, this is a very big confusion that I have. I request you to answer it as soon as possible

[Yu Hao]

Hi,

Using the first bits or the last bits depends on the rule pre-defined.

In our lecture slides, we use the last bits:

You might find that some other materials online use the first bits. It is not incorrect, but you should follow what Prof. Lin taught in the lectures if you try to answer a question in this course.

Cheers,

Yu