[AVRO-1270] Emit default values from resolved reader during schema evolution/projection

• Type: Bug
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 1.7.4
• Component/s: c

Environment

avro-c, schema evolution, return default values for fields not present in writer schema.

• Tags: avro-c
• Assignee: Unassigned
• Reporter: Chris Laws
• Created: 02/Mar/13 02:02
• Updated: 27/Oct/20 17:46

Description

Default values are not being returned by a resolved reader schema for fields that were not present in the writer schema.

The code that demonstrates this issue can be found in this gist (https://gist.github.com/claws/5069264). It is a slightly modified version of an example by Douglas Creager.

The section of interest is the READER_SCHEMA_C where a new field is added (to simulate schema evolution). In the main function the line:

read_with_schema_resolution(FILENAME, READER_SCHEMA_C, "c");

which is intended to display the default value for field 'c', as this field is not present in the writer schema. This does not happen. Instead an error is reported:

Error: Reader field c doesn't appear in writer

This error indicates that the avro-c implementation does not appear to support returning default values.

While posting about my avro problems on the avro user mailing list Douglas Creager indicated that the avro-c implementation does not support this functionality and suggested that a JIRA issue be raised.