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

["Zuyu Zhang (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/QUICKSTEP-89?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Zuyu Zhang resolved QUICKSTEP-89.
---------------------------------
    Resolution: Fixed

> 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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