[jira] [Commented] (ORC-1376) [C++] Support schema evolution

["Yuanping Wu (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ORC-1376?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17691367#comment-17691367 ] 

Yuanping Wu commented on ORC-1376:
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I‘d like to work on it.

> [C++] Support schema evolution
> ------------------------------
>
>                 Key: ORC-1376
>                 URL: https://issues.apache.org/jira/browse/ORC-1376
>             Project: ORC
>          Issue Type: New Feature
>          Components: C++
>            Reporter: Gang Wu
>            Priority: Major
>
> The Java ORC reader supports schema evolution by comparing readSchema with fileSchema [1] and creates a set of ConvertTreeReaders [2] to do the conversion. The conversion happens when reading columnar data into vector and evaluating expressions for predicate push down. The C++ reader does not support it yet.
> The type conversion on the Java side originates from Apache Hive. We should define what conversions are supposed to implement on the C++ side.
> [1] https://github.com/apache/orc/blob/main/java/core/src/java/org/apache/orc/impl/SchemaEvolution.java
> [2] https://github.com/apache/orc/blob/main/java/core/src/java/org/apache/orc/impl/ConvertTreeReaderFactory.java#L60:14



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