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From Rick Hillegas <rick.hille...@oracle.com>
Subject Re: Data Compression for Query Processing
Date Tue, 06 Sep 2011 14:49:23 GMT
Hi Reka,

Can you give us more detail about what you are trying to achieve? That 
may help us figure out what the right touchpoints are. Are you trying to 
achieve any of the following:

1) More aggressive garbage-collection of deleted rows...

2) More compact storage of columns...

3) More compact storage of rows...

4) More compact storage of pages...

5) Something else...


On 9/6/11 7:07 AM, Reka Thirunavukkarasu wrote:
> Hi all,
> We are from university of Moratuwa,Sri lanka.We are willing to apply
> data compression to Derby in query processing
> as requirement of our Advanced Database course project.
> Currently Derby has facility to trim the free space in raw data
> system procedure).Our goal is to apply data compression(Run-length
> encoding Compression) for each of values(not field name)
> of a query before executing and decompressing the data
>   when the execution finishes.
> Initially we went through the code base and identified that the data
> compression can be applied within the executeStatement()
> method of org.apache.derby.impl.jdbc.EmbedStatement class before
> calling ps.execute(),and we thought Using getParameterValueSet()
> method of Activation class the the attribute values of the parsed
> query can be obtained.But when we try to print the contents of the
> ParameterValueSet for typical insert query
> ,it is printing null(it is just empty set).
> We are expecting help from community regarding following questions.
> 1)What is wrong with point we identified to apply compression?
> 2)By applying compression before executing query,will the query
> execution process be affected?
> 3)Are there any possible place to apply compression and decompression
> before executing query?
> Thank you.
> -Reka

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