U-SQL custom extractor on custom row delimiter and json

Question

I have several text files with the following data structure:

{
huge 
json 
block that spans across multiple lines
}
--#newjson#--
{
huge 
json 
block that spans across multiple lines
}
--#newjson#--
{
huge 
json 
block that spans across multiple lines
} etc....

So it is actually json blocks that are row delimited by "--##newjson##--" string . I am trying to write a customer extractor to parse this. The problem is that I can't use string data type to feed json deserializer because it has a maximum size of 128 KB and the json blocks do not fit in this. What is the best approach to parse this file using a custom extractor?

I have tried using the code below, but it doesn't work. Even the row delimiter "--#newjson#--" doesn't seem to work right.

public SampleExtractor(Encoding encoding, string row_delim = "--#newjson#--", char col_delim = ';')
{
    this._encoding = ((encoding == null) ? Encoding.UTF8 : encoding);
    this._row_delim = this._encoding.GetBytes(row_delim);
    this._col_delim = col_delim;
}

public override IEnumerable<IRow> Extract(IUnstructuredReader input, IUpdatableRow output)
{ 
    //Read the input  by json
    foreach (Stream current in input.Split(_encoding.GetBytes("--#newjson#--")))
    {
        var serializer = new JsonSerializer();

        using (var sr = new StreamReader(current))
        using (var jsonTextReader = new JsonTextReader(sr))
        {
            var jsonrow = serializer.Deserialize<JsonRow>(jsonTextReader); 
            output.Set(0, jsonrow.status.timestamp);
        }
        yield return output.AsReadOnly();
    }
} 

Answer 1

You dont need a custom extractor to do that.

The best solution is add one json by line. Then you can use a text extractor and extract line by line. You can also pick your own delimiter.

REFERENCE ASSEMBLY [Newtonsoft.Json];
REFERENCE ASSEMBLY [Microsoft.Analytics.Samples.Formats];

    @JsonLines= 
        EXTRACT 
            [JsonLine] string
        FROM
            @Full_Path
        USING 
            Extractors.Text(delimiter:'\b', quoting : false);


@ParsedJSONLines = 
    SELECT 
        Microsoft.Analytics.Samples.Formats.Json.JsonFunctions.JsonTuple([JsonLine]) AS JSONLine
    FROM 
        @JsonLines

@AccessToProperties=
    SELECT 
        JSONLine["Property"] AS Property
    FROM 
        @ParsedJSONLines;

Answer 2

Here is how you can achieve the solution:

1) Create a c# equivalent of your JSON object Note:- Assuming all your json object are same in your text file. E.g:

Json Code

{
        "id": 1,
        "value": "hello",
        "another_value": "world",
        "value_obj": {
            "name": "obj1"
        },
        "value_list": [
            1,
            2,
            3
        ]
    }

C# Equivalent

 public class ValueObj
    {
        public string name { get; set; }
    }

    public class RootObject
    {
        public int id { get; set; }
        public string value { get; set; }
        public string another_value { get; set; }
        public ValueObj value_obj { get; set; }
        public List<int> value_list { get; set; }
    }

2) Change your de-serializing code like below after you have done the split based on the delimiter

using (JsonReader reader = new JsonTextReader(sr))
{
    while (!sr.EndOfStream)
    {
        o = serializer.Deserialize<List<MyObject>>(reader);
    }
}

This would deserialize the json data in c# class object which would solve your purpose. Later which you can serialize again or print it in text or ...any file.

Hope it helps.