Queries with CASE expressions |
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Authors: | Jarek Gryz Qiong Wang Xiaoyan Qian Calisto Zuzarte |
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Affiliation: | (1) Department of Computer Science and Engineering, York University, Toronto, Canada;(2) IBM Laboratory, Toronto, Canada |
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Abstract: | In recent years more and more queries are generated automatically by query managers/builders with end-users providing only
specific parameters through GUIs. Queries generated automatically can be quite different from queries written by humans. In
particular, they contain non-declarative features, most notorious of which is the CASE expression. Current query optimizers are often ill-prepared for the new types of queries as they do not deal well with procedural
‘insertions’. In this paper, we discuss the inefficiencies of CASE expressions and present several new optimization techniques to address them. We also describe experimental evaluation of
the prototype implemented in DB2 UDB V8.2. |
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