[jira] [Comment Edited] (HIVE-18685) Add catalogs to metastore

["Alan Gates (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-18685?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16367853#comment-16367853 ] 

Alan Gates edited comment on HIVE-18685 at 3/5/18 5:18 PM:
-----------------------------------------------------------

{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 initially going to add catalogs to SQL.  In the first few patches, 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 will add this functionality, but it will be a little later.

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.


was (Author: alangates):
{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, Parser, Security, SQL
>    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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