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https://issues.apache.org/jira/browse/HIVE-20287?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16597324#comment-16597324
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Lars Francke commented on HIVE-20287:
-------------------------------------
The docs currently say:
??An external table describes the metadata / schema on external files. External
table files can be accessed and managed by processes outside of Hive. External
tables can access data stored in sources such as Azure Storage Volumes (ASV) or
remote HDFS locations. If the structure or partitioning of an external table is
changed, an [MSCK REPAIR TABLE
table_name|https://cwiki.apache.org/confluence/display/Hive/LanguageManual+DDL#LanguageManualDDL-RecoverPartitions(MSCKREPAIRTABLE)]
statement can be used to refresh metadata information.??
This makes it sound as if MSCK only works for external tables. Is that true?
I'd need to check. Is anyone certain?
> Document the differences between managed and external tables
> ------------------------------------------------------------
>
> Key: HIVE-20287
> URL: https://issues.apache.org/jira/browse/HIVE-20287
> Project: Hive
> Issue Type: Improvement
> Components: Documentation
> Reporter: Lars Francke
> Assignee: Lars Francke
> Priority: Major
>
> We should document all the differences between managed and external tables. I
> need everyone's help for that though.
> This is what I know:
> * ARCHIVE/UNARCHIVE - DDLTask - Only works for managed tables
> * TRUNCATE - DDLSemanticAnalyzer - Only works for managed tables
> * MERGE/CONCATENATE - HiveRelOpMaterializationValidator - Only works for
> managed tables
> * Constraints - DDLSemanticAnalyzer - (NOT NULL, DEFAULT, CHECK, only RELY
> ist allowed)
> * IMPORT - ImportSemanticAnalyzer - This has some wild restrictions I didn't
> follow for external tables
> * Query Results Caching - https://issues.apache.org/jira/browse/HIVE-18513
> SemanticAnalyzer
>
> Hortonworks has extra documentation listing these things:
> * Query cache
> * Materialized views, except in a limited way
> * Default statistics gathering
> * Compute queries using statistics
> * Automatic runtime filtering
> * File merging after insert
>
> It'd be great if someone (from Hortonworks or otherwise) could elaborate on
> those.
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