Re: calculate size of idx

On 02/16/2004 11:36:03 PM, "Kommareddy, Srinivas (MED, Wissen Infotech)" wrote:
> want to add space to index tablespace also... (most of the indexes
> columns are NUMBER, should I take 32 bytes * n rows to calculate the
> size )
>

How did you arrive to 32 bytes? rowid is 10 bytes, so you have 10+vsize(key1)+vsize(key2)+vsize(key3)+...+vsize(keyn) for the leaf block entry. For non-leaf blocks, you have to add approximately 20% overhead (I use that number, it's a good approximation). That is, of course, a B-tree index. I don't know how to calculate bitmap index size. My guestimate, pulled out of my left thumb would be 20% of the size of the coresponding B-tree index. After all, disks are cheap, especially if somebody else pays for them.

-- 
Mladen Gogala
Oracle DBA
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