pratyakshsharma commented on a change in pull request #2424:
URL: https://github.com/apache/hudi/pull/2424#discussion_r556745181
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File path: hudi-common/src/main/java/org/apache/hudi/avro/HoodieAvroUtils.java
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@@ -292,53 +292,53 @@ public static GenericRecord stitchRecords(GenericRecord
left, GenericRecord righ
return result;
}
- /**
- * Given a avro record with a given schema, rewrites it into the new schema
while setting fields only from the old
- * schema.
- */
- public static GenericRecord rewriteRecord(GenericRecord record, Schema
newSchema) {
- return rewrite(record, getCombinedFieldsToWrite(record.getSchema(),
newSchema), newSchema);
- }
-
/**
* Given a avro record with a given schema, rewrites it into the new schema
while setting fields only from the new
* schema.
+ * NOTE: Here, the assumption is that you cannot go from an evolved schema
(schema with (N) fields)
+ * to an older schema (schema with (N-1) fields). All fields present in the
older record schema MUST be present in the
+ * new schema and the default/existing values are carried over.
+ * This particular method does the following things :
+ * a) Create a new empty GenericRecord with the new schema.
+ * b) For GenericRecord, copy over the data from the old schema to the new
schema or set default values for all fields of this
+ * transformed schema
+ * c) For SpecificRecord, hoodie_metadata_fields have a special treatment.
This is done because for code generated
+ * AVRO classes (HoodieMetadataRecord), the avro record is a
SpecificBaseRecord type instead of a GenericRecord.
+ * SpecificBaseRecord throws null pointer exception for record.get(name) if
name is not present in the schema of the
+ * record (which happens when converting a SpecificBaseRecord without
hoodie_metadata_fields to a new record with it).
+ * In this case, we do NOT set the defaults for the hoodie_metadata_fields
explicitly, instead, the new record assumes
+ * the default defined in the AvroSchema itself.
Review comment:
AvroSchema -> avro schema.
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