eolivelli commented on pull request #9614:
URL: https://github.com/apache/pulsar/pull/9614#issuecomment-784869893
@codelipenghui @congbobo184
When you are inside a Sink<GenericRecord> you have this situation and you
can access all of the schema info from the `Record`
```
Record<GenericRecord> record = ....;
GenericRecord value = record.getValue();
SchemaInfo schemaInfo = record.getSchema().getSchemaInfo();
SchemaType type = schemaInfo.getType();
value.getFields().forEach( f -> {
org.apache.avro.Schema.Field avroField =
f.unwrap(org.apache.avro.Schema.Field.class);
org.apache.avro.Schema fieldSchema = avroField.schema();
log.info("Field {} unwrapped as {} schema {}", f, avroField,
fieldSchema);
});
```
Unfortunately GenericRecord is used both to receive and to send values
from/to Pulsar.
We cannot easily add `GenericRecord#getSchema`
We already have `GenericRecord#getSchemaVersion` and this is already akward
for people that use GenericRecord to produce messages.
Do you think we should add something like
```
interface GenericRecord {
/**
* Access Schema information from the underlying Schema implementation.
* This API is useful only while receiving messages.
* Returns null in case that the requested Schema type is not available
*/
default <T> T unwrapSchema(Class<T> schemaType) {
return null;
}
/**
* Access Schema information.
* This API is useful only while receiving messages.
* Returns null in case that the requested information is not
available.
*/
default Optional<SchemaInfo> getSchemaInfo() {
return Options.empty();
}
}
```
I will also like it, as it will help users that are not inside a Sink and
they are receiving messages with the `Consumer` or `Reader` API.
In that case I would make `getSchemaVersion()` an optional method by adding
a default implementation and adding a note on the JavaDoc that the method is
intended to be used only while receiving messages.
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