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https://issues.apache.org/jira/browse/HIVE-11981?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14971476#comment-14971476
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Prasanth Jayachandran commented on HIVE-11981:
----------------------------------------------
This is what I expect to see in TreeReaderFactory (please let me know if I am
missing some feature that requires more changes to reader)
{code}
Object next(Object previous) {
..
Object result = null;
if (previous == null) {
result = new OrcStruct(columnCount); // this should be from file metadata as
we don't what schema that reader what hence we use file schema column count
(hive does not use this codepath)
} else {
// here we fill all the columns from the underlying file schema. If we see
more columns in the provided OrcStruct then we just null it out
}
..
}
{code}
> ORC Schema Evolution Issues (Vectorized, ACID, and Non-Vectorized)
> ------------------------------------------------------------------
>
> Key: HIVE-11981
> URL: https://issues.apache.org/jira/browse/HIVE-11981
> Project: Hive
> Issue Type: Bug
> Components: Hive, Transactions
> Reporter: Matt McCline
> Assignee: Matt McCline
> Priority: Critical
> Attachments: HIVE-11981.01.patch, HIVE-11981.02.patch,
> HIVE-11981.03.patch, HIVE-11981.05.patch, HIVE-11981.06.patch,
> HIVE-11981.07.patch, HIVE-11981.08.patch, HIVE-11981.09.patch, ORC Schema
> Evolution Issues.docx
>
>
> High priority issues with schema evolution for the ORC file format.
> Schema evolution here is limited to adding new columns and a few cases of
> column type-widening (e.g. int to bigint).
> Renaming columns, deleting column, moving columns and other schema evolution
> were not pursued due to lack of importance and lack of time. Also, it
> appears a much more sophisticated metadata would be needed to support them.
> The biggest issues for users have been adding new columns for ACID table
> (HIVE-11421 Support Schema evolution for ACID tables) and vectorization
> (HIVE-10598 Vectorization borks when column is added to table).
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