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From Matt Burgess <mattyb...@apache.org>
Subject Re: Nifi vs Sqoop
Date Thu, 10 Nov 2016 14:32:29 GMT
Nicolas,

The Max Value Columns property of QueryDatabaseTable is the
specification by which the processor fetches only the new lines. In
your case you would put "lastmodificationdate" as the Max Value
Column. The first time the processor is triggered, it will execute a
"SELECT * from myTable" and get all the rows (as it does not yet know
about "new" vs "old" rows). Then for the Max Value Column, it will
keep track of the maximum value currently observed for that column.
The next time the processor is triggered, it will execute a "SELECT *
FROM myTable WHERE lastModificationDate > the_max_value_seen_so_far".
Thus only rows whose value for the Max Value Column is greater than
the current maximum will be returned. Then the maximum is again
updated, and so on.

Does this answer your question(about QueryDatabaseTable)? If not
please let me know.

If your source table is large and/or you'd like to parallelize the
fetching of rows from the table, consider the GenerateTableFetch
processor [1] instead. Rather than _executing_ SQL like
QueryDatabaseTable does, GenerateTableFetch _generates_ SQL, and will
generate a number of flow files, each containing a SQL statement that
grabs X rows from the table. If you supply a Max Value Column here, it
too will perform incremental fetch after the initial one. These flow
files can be distributed throughout your cluster (using a
RemoteProcessGroup pointing to the same cluster, and an Input Port to
receive the flow files), creating a parallel distributed fetch
capability like Sqoop. From a scaling perspective, Sqoop uses
MapReduce so it can scale with the size of your Hadoop cluster.
GenerateTableFetch can scale to the size of your NiFi cluster. You
might choose NiFi or Sqoop based on the volume and velocity of your
data.

Regards,
Matt

[1] https://nifi.apache.org/docs/nifi-docs/components/org.apache.nifi.processors.standard.GenerateTableFetch/index.html

On Wed, Nov 9, 2016 at 4:37 AM, Provenzano Nicolas
<nicolas.provenzano@gfi.fr> wrote:
> Hi all,
>
>
>
> I have the following requirements :
>
>
>
> ·         I need to load at day 1 a full SQL table,
>
> ·         And then need to incrementally load new data (using capture data
> change mechanism).
>
>
>
> Initially, I was thinking using Sqoop to do it.
>
>
>
> Looking at Nifi and especially the QueryDatabaseTable processor, I’m
> wondering if I could use Nifi instead.
>
>
>
> Has someone already compared both to do it and what were the outcomes ?
>
>
>
> I can’t see however how to configure the QueryDatabaseTable to handle the
> new lines (for example, looking at a “lastmodificationdate” field and taking
> only the lines for which lastModificationDate > lastRequestDate) ?
>
>
>
> Thanks in advance
>
>
>
> BR
>
>
>
> Nicolas

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