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From Reka Thirunavukkarasu <rthirunavukkaras...@gmail.com>
Subject Data Compression for Query Processing
Date Tue, 06 Sep 2011 14:07:30 GMT
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
container(using SYSCS_UTIL.SYSCS_COMPRESS_TABLE
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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