[jira] [Updated] (ARROW-8464) [Rust] [DataFusion] Add better and faster support for dictionary types

["Andrew Lamb (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ARROW-8464?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Andrew Lamb updated ARROW-8464:
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    Summary: [Rust] [DataFusion] Add better and faster support for dictionary types  (was: [Rust] [DataFusion] Add support for dictionary types)

> [Rust] [DataFusion] Add better and faster support for dictionary types
> ----------------------------------------------------------------------
>
>                 Key: ARROW-8464
>                 URL: https://issues.apache.org/jira/browse/ARROW-8464
>             Project: Apache Arrow
>          Issue Type: Improvement
>          Components: Rust - DataFusion
>            Reporter: Andy Grove
>            Priority: Major
>
> Usecases: Efficiently process large columns of low cardinality Strings
>  
>  * BatchIterator should accept both DictionaryBatch and RecordBatch
>  * Type Coercion optimizer rule should inject expression for converting dictionary value types to index types (for equality expressions, and IN(values, ...)
>  * Physical expression would lookup index for dictionary values referenced in the query so that at runtime, only indices are being compared per batch



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