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From ajithsri <ajith...@gmail.com>
Subject Re: Data Compression for Query Processing
Date Thu, 15 Sep 2011 16:31:11 GMT


Since the compression is attribute level. can someone help to locate the
places where i need to add the compression(insert query) and
decompression(select query) codes?

for testing: just add the compression technique to VarChar data types(in
SQLVarchar class), so when calling "insert into mytable values ('my
string');" it compressed and stored. 
can someone help to find the place to apply the decompression method for
select query?

thanks in advance.

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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