Could any one please tell me the purpose of "Extent Index" in more detail
In Index types, I can see "Extent Index", Please tell me in detail about it
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see: https://docs.intersystems.com/iris20241/csp/docbook/Doc.View.cls?KEY=RGOT_complete
browser search "Extent Index"
Consider a persistent class of MyObjects with a bitmap index on Property1, and then have a subclass of MySpecialObjects.
If I use
select * from MySpecialObjects where Property1 = 'Something'
I only want the items that are MySpecialObjects and not any other MyObjects. The extent index makes this possible. It ANDs the MySpecialObjects extent index with the Property1 index.
A bonus, is it also makes select count(*) very fast, even with tables of over 50,000,000,000 rows
Thanks for your inputs.
Sorry - I just read Matt Gage's reply. My reply is redundant.