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https://issues.apache.org/jira/browse/HIVE-18685?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16367853#comment-16367853
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Alan Gates commented on HIVE-18685:
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{quote}Until this is determined, what will guard against a DML that does cross
catalogs? There is nothing in the above discussion about Lock Managers which
don't understand catalog concept.
{quote}
I am not going to add catalogs to SQL. It will not be possible to address a
table as catalog.database.table. Which catalog you are connected to will be
determine when the session is started and is immutable initially.
I do plan to add the catalog field to the transaction and lock tables that
track table names (anyplace where it tracks database and table now) so that it
can properly determine which tables are being handled. I will also need to
change the TxnHandler to deal with the catalog information and understand that
cat1.db.table != cat2.db.table.
I'm not certain at this point I ever want the lock and transaction code to
handle cross catalog operations. Catalog might be a good place to draw the
boundaries on locking and txns. But I haven't worked out the details of this
yet.
> Add catalogs to metastore
> -------------------------
>
> Key: HIVE-18685
> URL: https://issues.apache.org/jira/browse/HIVE-18685
> Project: Hive
> Issue Type: New Feature
> Components: Metastore
> Affects Versions: 3.0.0
> Reporter: Alan Gates
> Assignee: Alan Gates
> Priority: Major
> Attachments: HMS Catalog Design Doc.pdf
>
>
> SQL supports two levels of namespaces, called in the spec catalogs and
> schemas (with schema being equivalent to Hive's database). I propose to add
> the upper level of catalog. The attached design doc covers the use cases,
> requirements, and brief discussion of how it will be implemented in a
> backwards compatible way.
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