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https://issues.apache.org/jira/browse/HIVE-17361?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16273282#comment-16273282
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Alan Gates commented on HIVE-17361:
-----------------------------------
Put a couple of comments in review board.
> Support LOAD DATA for transactional tables
> ------------------------------------------
>
> Key: HIVE-17361
> URL: https://issues.apache.org/jira/browse/HIVE-17361
> Project: Hive
> Issue Type: New Feature
> Components: Transactions
> Reporter: Wei Zheng
> Assignee: Eugene Koifman
> Priority: Critical
> Attachments: HIVE-17361.07.patch, HIVE-17361.08.patch,
> HIVE-17361.09.patch, HIVE-17361.1.patch, HIVE-17361.10.patch,
> HIVE-17361.11.patch, HIVE-17361.12.patch, HIVE-17361.14.patch,
> HIVE-17361.16.patch, HIVE-17361.17.patch, HIVE-17361.19.patch,
> HIVE-17361.2.patch, HIVE-17361.20.patch, HIVE-17361.21.patch,
> HIVE-17361.23.patch, HIVE-17361.24.patch, HIVE-17361.25.patch,
> HIVE-17361.3.patch, HIVE-17361.4.patch
>
>
> LOAD DATA was not supported since ACID was introduced. Need to fill this gap
> between ACID table and regular hive table.
> Current Documentation is under [DML
> Operations|https://cwiki.apache.org/confluence/display/Hive/GettingStarted#GettingStarted-DMLOperations]
> and [Loading files into
> tables|https://cwiki.apache.org/confluence/display/Hive/LanguageManual+DML#LanguageManualDML-Loadingfilesintotables]:
> \\
> * Load Data performs very limited validations of the data, in particular it
> uses the input file name which may not be in 00000_0 which can break some
> read logic. (Certainly will for Acid).
> * It does not check the schema of the file. This may be a non issue for Acid
> which requires ORC which is self describing so Schema Evolution may handle
> this seamlessly. (Assuming Schema is not too different).
> * It does check that _InputFormat_S are compatible.
> * Bucketed (and thus sorted) tables don't support Load Data (but only if
> hive.strict.checks.bucketing=true (default)). Will keep this restriction for
> Acid.
> * Load Data supports OVERWRITE clause
> * What happens to file permissions/ownership: rename vs copy differences
> \\
> The implementation will follow the same idea as in HIVE-14988 and use a
> base_N/ dir for OVERWRITE clause.
> \\
> How is minor compaction going to handle delta/base with original files?
> Since delta_8_8/_meta_data is created before files are moved, delta_8_8
> becomes visible before it's populated. Is that an issue?
> It's not since txn 8 is not committed.
> h3. Implementation Notes/Limitations (patch 25)
> * bucketed/sorted tables are not supported
> * input files names must be of the form 00000_0/00000_0_copy_1 - enforced.
> (HIVE-18125)
> * Load Data creates a delta_x_x/ that contains new files
> * Load Data w/Overwrite creates a base_x/ that contains new files
> * A '_metadata_acid' file is placed in the target directory to indicate it
> requires special handling on read
> * The input files must be 'plain' ORC files, i.e. not contain acid metadata
> columns as would be the case if these files were copied from another Acid
> table. In the latter case, the ROW_IDs embedded in the data may not make
> sense in the target table (if it's in a different cluster, for example).
> Such files may also have a mix of committed and aborted data.
> ** this could be relaxed later by adding info to the _metadata_acid file to
> ignore existing ROW_IDs on read.
> * ROW_IDs are attached dynamically at read time and made permanent by
> compaction. This is done the same way has handling of files that were
> written to a table before it was converted to Acid.
> * Vectorization is supported
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