What is the need to rebuild index in table?

Question

please bear with me if the question is too naive. What is the need for rebuilding an index in a Table. Tried in Google and here in Stack overflow ; but hardly able to find any information about that. Would be great if you guys can provide your thoughts on this. Any external link about this topic should also help. Thanks in advance.

Answer 1

With the exception of a few corner cases, there generally should not be any need to rebuild indexes on a regular basis for an Oracle database.

Richard Foote has written extensively on the subject.

I can't speak to Informix.

Answer 2

You have a few cases where a rebuild is required, for example when you drop a partition of a table where a global index is defined. Another example is when you have a function based index and the function has changed.

If you have many changes (i.e. inserts and deletes) on a table a rebuild can reduce the occupied space of index and thus improve the performance.

However, I don't see any need to rebuild all indexes in an application on regular basis.

Answer 3

hmm like for example when a non-leaf node has too many childs it will take relatively higher time to access them so thus re