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From Mark Payne <marka...@hotmail.com>
Subject Re: Converting between avro formats
Date Thu, 15 Jun 2017 13:09:01 GMT
Mika,

ConvertRecord won't work for this type of thing, as what you're really wanting to do is creating
some sort of
mapping from one schema to a completely different schema. ConvertRecord would have no way
of knowing that
it should create some intermediate 'attributes' Record and push the 'baz' field inside of
it. This processor is capable
of translating between 'like' schemas, such as converting the baz field from a String to an
Integer. But it's not able
to handle something like this were the schemas are not compatible.

So my first thought was to use UpdateRecord, exactly as Wes laid out here. That's not actually
going to work, either,
though, because the 'attributes' Record doesn't exist. If there were an 'attributes' Record
that did not have a value
for 'baz' then it would work okay, but it won't create that intermediate Record for you.

Unfortunately, one of the downsides to using Avro is that there just isn't much tooling around
it like there is around
a lot of other (older) data formats. That said, I would like to create a JoltTransformRecord
processor that would allow
you to use Jolt to do this sort of transformation. But I've not gotten to that yet. One possibility,
though, would be to use
ConvertRecord to convert your Avro data into JSON data, then use JoltTransform to transform
between the two schemas,
and then again use ConvertRecord to convert from JSON back to Avro.

It is a bit tedious, but may be your best bet for now.

Thanks
-Mark


On Jun 14, 2017, at 4:05 PM, Wes Lawrence <wesleyll505@gmail.com<mailto:wesleyll505@gmail.com>>
wrote:

You may have to use 1.3's 'UpdateRecord'.

You can set the 'Replacement Value Strategy' to 'Record Path Value', and add a custom property
of key '/attributes/baz' with a value of '/baz'.

That should convert from the input to output schemas.

--Wes

On Wed, Jun 14, 2017 at 2:57 PM, Mika Borner <nifi@my2ndhead.com<mailto:nifi@my2ndhead.com>>
wrote:
Hi

I'm struggling with a record conversion. Not sure if it's my lack of knowledge about AVRO
or if this even possible with the ConvertRecord processor.

My input record schema is:

{
  "name": "inputrecord",
  "namespace": "event",
  "type": "record",
  "fields": [
    { "name": "foo", "type": "string" },
    { "name": "bar", "type": "string" },
    { "name": "baz", "type": "string" }
  ]
}

My output record schema:

{
  "name": "outputrecord",
  "namespace": "event",
  "type": "record",
  "fields": [
    { "name": "foo", "type": "string" },
    { "name": "bar", "type": "string" },
    { "name": "attributes",
              "type": { "type": "record",
                "name": "attributes",
                "namespace": "event",
                "fields" : [
                           {"name": "baz", "type": "string"}
                           ]
              }
    }
  ]
}

So basically, I want to have baz as a child attribute under the "attributes" element.

Currently I'm only getting "null" values back. If I use the inputrecord as the output schema,
I'm getting a value back for baz.

Thanks for your help!

Mika>






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