Re: alter index rebuild (NOT ONLINE)

On Fri, 31 Oct 2003 15:33:11 +0000, Yong Huang wrote:

> Hi, Norman,

Afternoon Yong,

> As usual, sometimes we go too far in correcting myths and forget to
> mention those exceptional cases.

Don't I know it !

> Let's say the original poster's
> database is supposed to be read-only but analysts find incorrect
> data (this does happen sometimes). Updates or deletes are run and
> the database comes back to read-only. Then it may be worth
> rebuilding some huge indexes to save disk space and index scan time.

True, but I would imagine that any deletions will be reused by insertions or updates (to the indexed columns anyway) so maybe no rebuild is required. On the other hand, if there were huge amounts of data deleted then it is possible that complete index blocks were also emptied, in which case, they will be added back to the freelist(s) - again, no rebuild required. As ever, 'it depends' :o)

Tom Kyte claims only to have rebuilt 8 indexes in his career, so that's really how often indexes *need* rebuilding.

Cheers,
Norm.

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