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Avro >> mail # user >> Generic Avro Classification and Deserialization


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Public Network Services 2013-01-17, 22:11
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Miki Tebeka 2013-01-18, 18:49
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Public Network Services 2013-01-18, 23:48
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Re: Generic Avro Classification and Deserialization
Check out avro-tools. With this you can dump the schema for a file,
extract the metadata, or export it in several formats:

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Available tools:
      compile  Generates Java code for the given schema.
   fragtojson  Renders a binary-encoded Avro datum as JSON.
     fromjson  Reads JSON records and writes an Avro data file.
     fromtext  Imports a text file into an avro data file.
      getmeta  Prints out the metadata of an Avro data file.
    getschema  Prints out schema of an Avro data file.
          idl  Generates a JSON schema from an Avro IDL file
       induce  Induce schema/protocol from Java class/interface via
reflection.
   jsontofrag  Renders a JSON-encoded Avro datum as binary.
      recodec  Alters the codec of a data file.
   rpcreceive  Opens an RPC Server and listens for one message.
      rpcsend  Sends a single RPC message.
       tether  Run a tethered mapreduce job.
       tojson  Dumps an Avro data file as JSON, one record per line.
       totext  Converts an Avro data file to a text file.
  trevni_meta  Dumps a Trevni file's metadata as JSON.
trevni_random  Create a Trevni file filled with random instances of a
schema.
trevni_tojson  Dumps a Trevni file as JSON.

-Terry

On 01/17/2013 05:11 PM, Public Network Services wrote:
> Folks,
>
> I am involved in a project to extract data from a large number of files
> (to be provided at some point), in numerous formats, among which is some
> Avro files (both binary and JSON-encoded), and thus I am looking for the
> best way to tackle this.
>
> One of the things we would (ideally) like to do is auto-classify the
> data generically, i.e. read a few lines or bytes off a file and be able
> to tell what kind of format it is.
>
> This is fairly easy to do with, say, (non-Avro) JSON files, but I am not
> sure how this would be done for Avro.
>
> For one thing, there is the necessity of a Schema, about which the
> documentation says that
>
>   * "Avro data is always serialized with its schema. Files that store
>     Avro data should always also include the schema for that data in the
>     same file."
>
> However, the Java code examples posted on the project website imply that
> the Schema is supplied as a separate file and I am not sure whether this
> is only the case with RPC.
>
> Are there any code examples for detecting the encoding format
> (binary/json) of the data file, assessing whether there is a schema
> embedded in it and extracting that schema?
>
> Thanks!
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Public Network Services 2013-01-19, 00:46
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Miki Tebeka 2013-01-19, 04:36