The docs say that "The merge tool is typically run after an incremental import with the date-last-modified mode (sqoop import --incremental lastmodified …)."
Also, I am not sure how the merge tool handles deleted records, looking at the code of merge tool, i don't think it deletes the corresponding records from target which were deleted in the source.

~Pratik

On Fri, Sep 19, 2014 at 8:43 AM, Radhe Radhe <radhe.krishna.radhe@live.com> wrote:
Hi Pratik,

The source RDBMs tables will not always necessarily contain a 'last-modified' column.

I see that 'sqoop-merge' is there:
The merge tool allows you to combine two datasets where entries in one dataset should overwrite entries of an older dataset. For example, an incremental import run in last-modified mode will generate multiple datasets in HDFS where successively newer data appears in each dataset. The mergetool will "flatten" two datasets into one, taking the newest available records for each primary key.

Can 'sqoop-merge' be used to get the updated rows somehow? Will that be a viable solution?

Thanks,
-RR

From: tispratik@gmail.com
Date: Fri, 19 Sep 2014 08:18:23 -0700
Subject: Re: Sqoop Incremental mode to get updated data in Hive
To: user@sqoop.apache.org


What other columns do you have in your table which can be used?
Either a last modified timestamp based column or a version id based column is needed for sqoop to know if something new came along
since the last import. Even if we were to write our own version of sqoop, we would still need that information.

Another option could have been to monitor the query logs of the RDBMS and batch the logs and then issue imports. But sqoop does not monitor the query logs.

~Pratik

On Fri, Sep 19, 2014 at 6:41 AM, Radhe Radhe <radhe.krishna.radhe@live.com> wrote:
Hello Experts,

I need to extract data from RDBMS tables to Hive Tables on a timely basis(daily/weekly, etc.).

My tables have a 'Primary Key' but does NOT have a 'last-modified' column.

I plan to go as:
FIRST RUN: Will use sqoop-import-all-tables command for importing all the tables at one go to Hive Tables.
EACH SUBSEQUENT RUN: Use Sqoop incremental import mode to retrieve only rows newer than some previously-imported set of rows.

My question is how can I get the updated rows which got updated in between the FIRST RUN and NEXT SUBSEQUENT RUN.
For e.g. 
Say in FIRST RUN: I fetched all tables. 
A CUSTOMER table that has 100 records with CustomerId as Primary Key(1 to 100) is imported to Hive CUSTOMER table.

And now meanwhile some rows in the Source CUSTOMER table got updated.
With my NEXT SUBSEQUENT RUN this will fetch rows > 100, thus skipping the updated rows which are  < 100. 

How can I get the updated rows on each subsequent run.

Referring to Sqoop documentation this strategy works only if we have a last-modified column(which in my case don't have):
An alternate table update strategy supported by Sqoop is called lastmodified mode. 
You should use this when rows of the source table may be updated, and each such update will set the value of a last-modified column to the current timestamp. 
Rows where the check column holds a timestamp more recent than the timestamp specified with --last-value are imported.

Any suggestions on how to get the updated data on SUBSEQUENT RUNS using the Sqoop Incremental mode?

Thanks,
-RR