[jira] [Created] (QUICKSTEP-89) Add support for common subexpression elimination.

["Jianqiao Zhu (JIRA)" <ji...@apache.org>]

Jianqiao Zhu created QUICKSTEP-89:
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             Summary: Add support for common subexpression elimination.
                 Key: QUICKSTEP-89
                 URL: https://issues.apache.org/jira/browse/QUICKSTEP-89
             Project: Apache Quickstep
          Issue Type: New Feature
          Components: Expressions, Query Optimizer, Relational Operators
            Reporter: Jianqiao Zhu
            Assignee: Jianqiao Zhu


This feature adds support for common subexpression elimination in Quickstep.

Note that Quickstep features column-at-a-time expression evaluation. So we use a relatively simple *memoization* approach that (1) identifies common subexpressions at query optimization time and assigns unique IDs for each equivalence class of common subexpressions, and (2) uses a memoization table (per block) to memorize and lookup result column vectors at query execution time based on the common subexpression IDs.



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