Re: C - AVRO - Array of records

[Gill, John]

Julian,
I think you are doing things backwards in the way you add the new element to 
your array.

You need to create the value based upon the element schema from 
logDataReferenceArray and then append it to the list.

Something like:
// Create the new element based on the element schema
element_iface = 
avro_generic_class_from_schema(avro_schema_array_items(avro_value_get_schema(logDataReferenceArray)));
avro_generic_value_new(element_iface, &element);

// Set the values in the element
avro_value_get_by_name(&element, "deviceType", &currentField, NULL);
avro_value_set_int(&currentField, 2);

avro_value_get_by_name(&element, "deviceId", &currentField, NULL);
avro_value_set_int(&currentField, 3);

// Append the newly created element to the list
avro_value_append(&logDataReferenceArray, &element, NULL),

Someone else on the list can correct me if I am wrong. But this is the only way 
I see to do it.

-- John


From: "Utsch Julian (AE-EB/ENS1)" <julian.ut...@de.bosch.com>
Reply-To: "user@avro.apache.org" <user@avro.apache.org>
Date: Wednesday, April 12, 2017 at 2:18 AM
To: "user@avro.apache.org" <user@avro.apache.org>
Subject: C - AVRO - Array of records


Hi together,

I'm trying to get familiar with 
AVRO<https://avro.apache.org/docs/1.8.1/spec.html> in C. I've defined an AVRO 
Schema (see below) with simple fields, which aren't the problem. But also there 
are an array of (sub)-records, which I can't access correctly. There are no 
compiler errors or other AVRO errors, but the AVRO file won't be filled with 
data... Without the array of (sub)-records, everything works fine.
Maybe some of you have an idea why my code isn’t still working. Therefore I 
can’t find any examples or documentations, which describe the procedure to fill 
subrecords with data.

PS: I've extracted only the important parts from the whole code; otherwise the 
code would be too long for here. So, I hope I didn't forget any necessary parts.

Thanks for your help. Best regards, Julian
Here the code:


const char METAFILE_SCHEMA[] =

"{\

  \"name\" : \"metafile\",\

  \"type\" : \"record\",\

  \"fields\" : [\

    { \"name\" : \"metaId\", \"type\" : \"long\" },\

    { \"name\" : \"logFilesCount\", \"type\" : \"int\" },\

    { \"name\" : \"logDataReference\", \"type\" : {\

        \"type\" : \"array\",\

        \"items\" : {\

          \"name\" : \"LogFileRef\",\

          \"type\" : \"record\",\

          \"fields\" : [\

            { \"name\" : \"deviceType\", \"type\" : \"int\" },\

            { \"name\" : \"deviceId\", \"type\" : \"int\" }\

            ]\

        }\

      }\

    },\

    { \"name\" : \"timestamp\", \"type\" : \"long\" }\

    ]\

}";



avro_file_writer_t file;



avro_schema_t metafile_schema;



avro_value_iface_t *metafile_iface;



avro_value_t metafile_record;



avro_value_t currentField;

avro_value_t element;

avro_value_t logDataReferenceArray;



if(avro_schema_from_json_literal(METAFILE_SCHEMA, &metafile_schema)) {

        fprintf(stderr, "Unable to parse metafile schema\n");

        exit(EXIT_FAILURE);

    }



 metafile_iface = avro_generic_class_from_schema(metafile_schema);

 try(avro_generic_value_new(metafile_iface, &metafile_record), "Error creating 
instance of metafile record");



 remove("metafile.avro");

 avro_file_writer_create("metafile.avro", metafile_schema, &file);



 int64_t metaId = 9999;

 avro_value_get_by_name(&metafile_record, "metaId", &currentField, NULL);

 avro_value_set_long(&currentField, metaId);



 avro_value_get_by_name(&metafile_record, "logDataReference", 
&logDataReferenceArray, NULL);

 try(avro_value_append(&logDataReferenceArray, &element, NULL), "Error in 
appending record in logdatareference array");

 avro_value_get_by_name(&element, "deviceType", &currentField, NULL);

 avro_value_set_int(&currentField, 2);

 avro_value_get_by_name(&element, "deviceId", &currentField, NULL);

 avro_value_set_int(&currentField, 3);



avro_file_writer_append_value(file, &metafile_record);



avro_file_writer_close(file);



avro_schema_decref(metafile_schema);



avro_value_decref(&metafile_record);



avro_value_iface_decref(metafile_iface);