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From Russell Jurney <russell.jur...@gmail.com>
Subject Re: AvroStorage/Avro Schema Question
Date Tue, 10 Apr 2012 09:36:04 GMT
Hmmmm unable to get this to work:

{
    "namespace": "agile.data.avro",
    "name": "Email",
    "type": "record",
    "fields": [
        {"name":"message_id", "type": ["string", "null"]},
        {"name":"froms","type": [{"type":"record", "name":"from", "fields":
[{"type":"array", "items":"string"}, "null"]}, "null"]},
        {"name":"tos","type": [{"type":"record", "name":"to", "fields":
[{"type":"array", "items":"string"}, "null"]}, "null"]},
        {"name":"ccs","type": [{"type":"record", "name":"cc", "fields":
[{"type":"array", "items":"string"}, "null"]}, "null"]},
        {"name":"bccs","type": [{"type":"record", "name":"bcc", "fields":
[{"type":"array", "items":"string"}, "null"]}, "null"]},
        {"name":"reply_tos","type": [{"type":"record", "name":"reply_to",
"fields": [{"type":"array", "items":"string"}, "null"]}, "null"]},
        {"name":"in_reply_to", "type": [{"type":"array", "items":"string"},
"null"]},
        {"name":"subject", "type": ["string", "null"]},
        {"name":"body", "type": ["string", "null"]},
        {"name":"date", "type": ["string", "null"]}
    ]
}

On Tue, Apr 10, 2012 at 2:26 AM, Russell Jurney <russell.jurney@gmail.com>wrote:

> In thinking about it more... it seems that unfortunately, the only thing I
> can really do is to change the schema for all email address fields:
>
> {"name":"from","type": [{"type":"array", "items":"string"}, "null"]},
> to:
> {"name":"froms","type": [{"type":"record", "name":"from", "fields":
> [{"type":"array", "items":"string"}, "null"]}, "null"]},
>
> That is, to pluralize everything and then individually name array
> elements. I will try running this through my stack.
>
>
> On Mon, Apr 2, 2012 at 9:13 AM, Scott Carey <scottcarey@apache.org> wrote:
>
>> It appears as though the Avro to PigStorage schema translation names (in
>> pig) all arrays ARRAY_ELEM.  The nullable wrapper is 'visible' and the
>> field name is not moved onto the bag name.
>>
>> About a year and a half ago I started
>> https://issues.apache.org/jira/browse/AVRO-592
>>
>> but before finishing it AvroStorage was written elsewhere.  I don't
>> recall exactly what I did with the schema translation there, but I recall
>> the mapping from an Avro schema to pig tried to hide the nullable wrappers
>> more.
>>
>>
>> In Avro, arrays are unnamed types, so I see two things you could probably
>> do without any code changes:
>>
>> * Add a line in the pig script to project / rename the fields to what you
>> want (unfortunate and clumbsy, but I think it will work — I think you want
>> "from::PIG_WRAPPER::ARRAY_ELEM as from"  or
>> "FLATTEN(from::PIG_WRAPPER)::ARRAY_ELEM as from" something like that.
>> * Add a record wrapper to your schema (which may inject more messiness in
>> the pig schema view):
>> {
>>     "namespace": "agile.data.avro",
>>     "name": "Email",
>>     "type": "record",
>>     "fields": [
>>         {"name":"message_id", "type": ["string", "null"]},
>>         {"name":"from","type": [{"type":"record", "name":"From",
>> "fields": [[{"type":"array", "items":"string"},"null"]], "null"]},
>>        …
>>     ]
>> }
>>
>> But that is very awkward — requiring a named record for each field that
>> is an unnamed type.
>>
>>
>> Ideally PigStorage would treat any union of null and one other thing as a
>> simple pig type with no wrapper, and project the name of a field or record
>> into the name of the thing inside a bag.
>>
>>
>> -Scott
>>
>> On 3/29/12 6:05 PM, "Russell Jurney" <russell.jurney@gmail.com> wrote:
>>
>> Is it possible to name string elements in the schema of an array?
>>  Specifically, below I want to name the email addresses in the
>> from/to/cc/bcc/reply_to fields, so they don't get auto-named ARRAY_ELEM by
>> Pig's AvroStorage.  I know I can probably fix this in Java in the Pig
>> AvroStorage UDF, but I'm hoping I can also fix it more easily in the
>> schema.  Last time I read Avro's array docs in this context, my hit-points
>> dropped by a third, so pardom me if I've not rtfm this time :)
>>
>> Complete description of what I'm doing follows:
>>
>> Avro schema for my emails:
>>
>> {
>>     "namespace": "agile.data.avro",
>>     "name": "Email",
>>     "type": "record",
>>      "fields": [
>>         {"name":"message_id", "type": ["string", "null"]},
>>         {"name":"from","type": [{"type":"array", "items":"string"},
>> "null"]},
>>         {"name":"to","type": [{"type":"array", "items":"string"},
>> "null"]},
>>         {"name":"cc","type": [{"type":"array", "items":"string"},
>> "null"]},
>>         {"name":"bcc","type": [{"type":"array", "items":"string"},
>> "null"]},
>>         {"name":"reply_to", "type": [{"type":"array", "items":"string"},
>> "null"]},
>>         {"name":"in_reply_to", "type": [{"type":"array",
>> "items":"string"}, "null"]},
>>         {"name":"subject", "type": ["string", "null"]},
>>         {"name":"body", "type": ["string", "null"]},
>>         {"name":"date", "type": ["string", "null"]}
>>     ]
>> }
>>
>>
>> Pig to publish my Avros:
>>
>> grunt> emails = load '/me/tmp/emails' using AvroStorage();
>> grunt> describe emails
>>
>> emails: {message_id: chararray,from: {PIG_WRAPPER: (ARRAY_ELEM:
>> chararray)},to: {PIG_WRAPPER: (ARRAY_ELEM: chararray)},cc: {PIG_WRAPPER:
>> (ARRAY_ELEM: chararray)},bcc: {PIG_WRAPPER: (ARRAY_ELEM:
>> chararray)},reply_to: {PIG_WRAPPER: (ARRAY_ELEM: chararray)},in_reply_to:
>> {PIG_WRAPPER: (ARRAY_ELEM: chararray)},subject: chararray,body:
>> chararray,date: chararray}
>>
>> grunt> store emails into 'mongodb://localhost/agile_data.emails' using
>> MongoStorage();
>>
>>
>> My emails in MongoDB:
>>
>> > db.emails.findOne()
>> {
>> "_id" : ObjectId("4f738a35414e113e75707b97"),
>> "message_id" : "<4f71abddc19ec_145449e3898474d2@li169-134.mail>",
>>  "from" : [
>> {
>> "ARRAY_ELEM" : "daily@jobchangealerts.com"
>>  }
>> ],
>> "to" : [
>> {
>>  "ARRAY_ELEM" : "Russell.jurney@gmail.com"
>> }
>>  ],
>> "cc" : null,
>> "bcc" : null,
>> "reply_to" : null,
>>  "in_reply_to" : null,
>> "subject" : "Daily Job Change Alerts from SalesLoft",
>> "body" : "Daily Job Change Alerts from SalesLoft",
>>  "date" : "2012-03-27T08:00:29"
>> }
>>
>>
>> My email on screen:
>>
>> [image: Inline image 1]
>>
>> My face when I see ARRAY_ELEM, because it means more complex presentation
>> code: *:(*
>> --
>> Russell Jurney twitter.com/rjurney russell.jurney@gmail.com datasyndrome.
>> com
>>
>>
>
>
> --
> Russell Jurney twitter.com/rjurney russell.jurney@gmail.com datasyndrome.
> com
>



-- 
Russell Jurney twitter.com/rjurney russell.jurney@gmail.com datasyndrome.com

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