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https://issues.apache.org/jira/browse/BEAM-5967?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16827886#comment-16827886
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Alex Van Boxel commented on BEAM-5967:
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Design decision: Although DynamicMessage could in theory have a different
schema per message in a single stream this doesn't make sense. The common
use-case for using DynamicMessages is when the schema is *not known at compile
type*, build is *known at pipeline build time* (example, like pulled from a
schema registry).
With this restriction we only need to store the schema (or descriptor) once
when the pipeline is serialized and send to the workers.
> ProtoCoder doesn't support DynamicMessage
> -----------------------------------------
>
> Key: BEAM-5967
> URL: https://issues.apache.org/jira/browse/BEAM-5967
> Project: Beam
> Issue Type: Improvement
> Components: sdk-java-core
> Affects Versions: 2.8.0
> Reporter: Alex Van Boxel
> Assignee: Alex Van Boxel
> Priority: Major
> Labels: triaged
>
> The ProtoCoder does make some assumptions about static messages being
> available. The DynamicMessage doesn't have some of them, mainly because the
> proto schema is defined at runtime and not at compile time.
> Does it make sense to make a special coder for DynamicMessage or build it
> into the normal ProtoCoder.
> Here is an example of the assumtion being made in the current Codec:
> {code:java}
> try {
> @SuppressWarnings("unchecked")
> T protoMessageInstance = (T)
> protoMessageClass.getMethod("getDefaultInstance").invoke(null);
> @SuppressWarnings("unchecked")
> Parser<T> tParser = (Parser<T>) protoMessageInstance.getParserForType();
> memoizedParser = tParser;
> } catch (IllegalAccessException | InvocationTargetException |
> NoSuchMethodException e) {
> throw new IllegalArgumentException(e);
> }
> {code}
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