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https://issues.apache.org/jira/browse/AVRO-859?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13065521#comment-13065521
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Scott Carey commented on AVRO-859:
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Another feature that this symmetry brings:
Schema resolution will apply to any operation, not just 'read'.
A resolution applies from a schema 'source' to a schema 'target'. The source
could be an object graph, with the target another object graph or the source
could be bytes, and the target bytes. One could have an object graph
representing one schema and write it to bytes in a subset schema (projection on
write).
> Java: Data Flow Overhaul -- Composition and Symmetry
> ----------------------------------------------------
>
> Key: AVRO-859
> URL: https://issues.apache.org/jira/browse/AVRO-859
> Project: Avro
> Issue Type: New Feature
> Components: java
> Reporter: Scott Carey
> Assignee: Scott Carey
>
> Data flow in Avro is currently broken into two parts: Read and Write. These
> share many common patterns but almost no common code.
> Additionally, the APIs for this are DatumReader and DatumWriter, which
> requires that implementations know how to traverse Schemas and use the
> Resolver.
> This is a proposal to overhaul the inner workings of Avro Java between the
> Decoder/Encoder APIs and DatumReader/DatumWriter such that there is
> significantly more code re-use and much greater opportunity for new features
> that can all share in general optimizations and dynamic code generation.
> The two primary concepts involved are:
> * _*Functional Composition*_
> * _*Symmetry*_
> h4. Functional Composition
> All read and write operations can be broken into functional bits and composed
> rather than writing monolithic classes. This allows a "DatumWriter2" to be a
> graph of functions that pre-compute all state required from a schema rather
> than traverse a schema for each write.
> h4. Symmetry
> Avro's data flow can be made symmetric. Rather than thinking in terms of
> Read and Write, think in terms of:
> * _*Source*_: Where data that is represented by an Avro schema comes from --
> this may be a Decoder, or an Object graph.
> * _*Target*_: Where data that represents an Avro schema is sent -- this may
> be an Encoder or an Object graph.
> (More detail in the comments)
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