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From "Jarek Cecho" <jar...@apache.org>
Subject Re: Review Request 17650: SQOOP-1278: Allow use of uncommitted isolation on databases that support is an import option
Date Tue, 04 Feb 2014 17:10:43 GMT


> On Feb. 3, 2014, 4:58 p.m., Jarek Cecho wrote:
> > Hi Venkat,
> > thank you very much for working on this one! Allowing user to set the transaction
isolation level seems to be good idea. I'm a bit concerned that the change is only in the
DBInputFormat and as a result it won't be utilized by connectors using their own input formats,
but I guess that there is not much we can do about that in Sqoop 1. Hopefully we will have
better situation in Sqoop 2! Couple of high level notes:
> > 
> > 1) Do you think that it would be useful to let user set any transaction level? Right
now Sqoop allows only two, so perhaps allowing all of them might be useful?
> > 2) Do you think that it would be useful to set the transaction isolation also for
connections created from within the Sqoop process (e.g. while fetching metadata, ...).
> > 3) Would you mind documenting the new option in the user guide?
> > 
> > Jarcec
> 
> Venkat Ranganathan wrote:
>     Good questions Jarcec.  Thanks for the quick review also.
>     
>     1)  While it may seem that it may seem good to allow all isolation levels, the other
isolation levels (repeatable read and serializable) have increased transaction isolation requirements
and may not be really useful
>     2)  Metadata queries can be read committed (internally some DBMSs do use recursive
queries for them) and show that should be fine.   For those queries using the connection to
get the result set metadata (like 1=0 clause query) do not end up in acquiring any locks so
should be OK as it is
>     3)  Will definitely add doc.  Sorry for missing it
>

Thank you for the answers Venkat, makes complete sense to me.


- Jarek


-----------------------------------------------------------
This is an automatically generated e-mail. To reply, visit:
https://reviews.apache.org/r/17650/#review33434
-----------------------------------------------------------


On Feb. 3, 2014, 8:01 p.m., Venkat Ranganathan wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/17650/
> -----------------------------------------------------------
> 
> (Updated Feb. 3, 2014, 8:01 p.m.)
> 
> 
> Review request for Sqoop.
> 
> 
> Bugs: SQOOP-1278
>     https://issues.apache.org/jira/browse/SQOOP-1278
> 
> 
> Repository: sqoop-trunk
> 
> 
> Description
> -------
> 
> Allow the use of read uncommitted isolation on all databases that support it.  Oracle
does not read uncommitted as a settable option in the JDBC drivers so it will behave as before
on Oracle.
> 
> 
> Diffs
> -----
> 
>   src/docs/user/common-args.txt 8a017f4 
>   src/docs/user/import.txt 0db6d97 
>   src/java/org/apache/sqoop/SqoopOptions.java 46e158c 
>   src/java/org/apache/sqoop/mapreduce/DataDrivenImportJob.java b21560e 
>   src/java/org/apache/sqoop/mapreduce/db/DBConfiguration.java be942ce 
>   src/java/org/apache/sqoop/mapreduce/db/DBInputFormat.java 73ed94e 
>   src/java/org/apache/sqoop/tool/BaseSqoopTool.java 6d6f1ea 
>   src/test/com/cloudera/sqoop/TestSqoopOptions.java 686d398 
> 
> Diff: https://reviews.apache.org/r/17650/diff/
> 
> 
> Testing
> -------
> 
> One new test to test the option.  Explicitly tested with Oracle, DB2 and Postgresql.
  All unit tests passed
> 
> 
> Thanks,
> 
> Venkat Ranganathan
> 
>


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