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From Oystein.Grov...@Sun.COM (Øystein Grøvlen)
Subject Re: Behaviour of SYSCS_COMPRESS_TABLE
Date Wed, 01 Jun 2005 14:11:30 GMT
>>>>> "TW" == The Wogster <wogsterca@yahoo.ca> writes:

    TW> Øystein Grøvlen wrote:

    >> Is this also true for B-tree indexes?  I would imagine that if you
    >> have a index on a monotocally increasing key (e.g., a timestamp) and
    >> where you regularly delete old records, there may be a lot of empty
    >> B-tree pages that will never be possible to reuse.
    >> 


    TW> What happens in most databases. is  that the database has a fixed page
    TW> size, say 8K, when  an index page is full, it splits  that page into 2
    TW> half pages. When an index page  is empty it's dropped from the index,
    TW> and  added to  the  empty page  pool.  Many will  merge almost  empty
    TW> neighbouring pages, but that doesn't matter for this discussion.

I know this.  The reason I asked was because I have got the impression
that in Derby the only way to drop empty index pages is to do
compression.

-- 
Øystein


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