Github user rick-ibm commented on the pull request:

    https://github.com/apache/spark/pull/9202#issuecomment-152638711
  
    Thanks for that feedback, Michael. To answer your question:
    
    MA> I haven't looked closely at the implementation, but one high level 
question is whether this is breaking the use case where a users gives a 
subquery instead of a table name (i.e. dbtable = (SELECT ...).) This is an 
important part of the API that we can't break.
    
    Reynold posed the same question at 
https://issues.apache.org/jira/browse/SPARK-10857?focusedCommentId=14967827&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14967827
 and I replied at 
https://issues.apache.org/jira/browse/SPARK-10857?focusedCommentId=14967930&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14967930
    
    Can you give me an example of the syntax you have in mind which might trip 
this problem? I tried the following experiment...
    
      val jdbcDF = sqlContext.read.format("jdbc").options( 
        Map("url" -> "jdbc:derby:/Users/rhillegas/derby/databases/derby1",
        "dbtable" -> "select * from app.t")).load()
    
    ...but that statement doesn't tickle JdbcDialect.getTableExistsQuery(). 
Instead, the statement fails because the following ungrammatical query is sent 
to the database:
    
      SELECT * FROM select * from app.t WHERE 1=0
    
    That, in turn, is because JDBCRDD.resolveTable() has its own hard-coded 
query which probes for the existence of a table. I have logged 
https://issues.apache.org/jira/browse/SPARK-11426 to track this issue. The 
header comment on JDBCRDD.resolveTable() indicates that the method expects a 
table name and not an arbitrary query.
    
    Thanks,
    -Rick



---
If your project is set up for it, you can reply to this email and have your
reply appear on GitHub as well. If your project does not have this feature
enabled and wishes so, or if the feature is enabled but not working, please
contact infrastructure at infrastruct...@apache.org or file a JIRA ticket
with INFRA.
---

---------------------------------------------------------------------
To unsubscribe, e-mail: reviews-unsubscr...@spark.apache.org
For additional commands, e-mail: reviews-h...@spark.apache.org

Reply via email to