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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-6574) Support nested catalogs in ExternalCatalog
Date Wed, 17 May 2017 06:27:04 GMT

    [ https://issues.apache.org/jira/browse/FLINK-6574?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16013608#comment-16013608
] 

ASF GitHub Bot commented on FLINK-6574:
---------------------------------------

Github user KurtYoung commented on a diff in the pull request:

    https://github.com/apache/flink/pull/3913#discussion_r116919169
  
    --- Diff: flink-libraries/flink-table/src/main/scala/org/apache/flink/table/catalog/ExternalCatalogTable.scala
---
    @@ -37,25 +36,10 @@ import org.apache.flink.table.plan.stats.TableStats
       * @param lastAccessTime       Timestamp of last access of the table
       */
     case class ExternalCatalogTable(
    -    identifier: TableIdentifier,
    --- End diff --
    
    If we don't have table identifier or table name, the `TableSourceConverter` will not work
when trying to convert `ExternalCatalogTable` to a real `TableSource`.
    
    Even if we keep the table name, i'm not sure it will work for all situations. For example,
if we have an outside catalog which have the notion of database, like MySQL. Table in that
catalog will named as "db1.table1" or "db2.table2". In the new design, normally we should
add database as the sub catalog of the root catalog. So we can create "table1" from sub-catalog
named "db1". The problem is the table name is assigned as "table1", we loose the information
that this table actually comes from "db1". This may cause some problems when the TableSource
trying to establish connection or trying to get table information from outside catalog. 


> Support nested catalogs in ExternalCatalog
> ------------------------------------------
>
>                 Key: FLINK-6574
>                 URL: https://issues.apache.org/jira/browse/FLINK-6574
>             Project: Flink
>          Issue Type: Bug
>          Components: Table API & SQL
>            Reporter: Haohui Mai
>            Assignee: Haohui Mai
>            Priority: Critical
>             Fix For: 1.3.0
>
>
> We found out that the current external catalog requires three layers of references for
any tables. For example, the SQL would look like the following when referencing external table:
> {noformat}
> SELECT * FROM catalog.db.table
> {noformat}
> It would be great to support only two layers of indirections which is closer to many
of the deployment on Presto / Hive today.
> {noformat}
> SELECT * FROM db.table
> {noformat}



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