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From aaron morton <aa...@thelastpickle.com>
Subject Re: Composite Column Types Storage
Date Fri, 14 Sep 2012 05:03:18 GMT
> Range queries do not use bloom filters. 
Are you talking about row range queries ? Or a slice of columns in a row ? 

If you are getting a slice of columns from a single row, a bloom filter is used to locate
the row. 
If you are getting a slice of columns from a range of rows, the bloom filter is used to locate
the first row. After that is a scan. 

There are also row level bloom filters for columns on a row. These are used when you columns
by names. If you are doing a slice with a start the bloom filter is not used, instead the
row level column index is used (if present). 

Hope that helps. 


-----------------
Aaron Morton
Freelance Developer
@aaronmorton
http://www.thelastpickle.com

On 13/09/2012, at 2:30 AM, Ravikumar Govindarajan <ravikumar.govindarajan@gmail.com>
wrote:

> Thanks for the clarification. Even though compression solves disk space issue, we might
still have Memtable bloat right?
> 
> There is another issue to be handled for us. The queries are always going to be range
queries with absolute match on part1 and range on part 2 of the composite columns
> 
> Ex: Query <some-key> <Column-part-1> <Start-Id-part-2> <Limit>

> 
> Range queries do not use bloom filters. It holds good for composite-columns also right?
I believe I will end up writing BF bytes only to skip it later.
> 
> If sharing had been possible, then <Column-part-1> alone could have gone into the
bloom-filter, speeding up my queries really effectively.
> 
> But as I understand, there are many levels of nesting possible in a composite type and
casing at every level is a big task
> 
> May be casing for the top-level or the first-part should be a good start?
> 
> --
> Ravi
> 
> On Wed, Sep 12, 2012 at 5:46 PM, Sylvain Lebresne <sylvain@datastax.com> wrote:
> > Is every <string>/<id> combination stored separately in disk
> 
> Yes, each combination is stored separately on disk (the storage engine
> itself doesn't have special casing for composite column, at least not
> yet). But as far as disk space is concerned, I suspect that sstable
> compression makes this largely a non issue.
> 
> --
> Sylvain
> 


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