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https://issues.apache.org/jira/browse/KAFKA-12925?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17361062#comment-17361062
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Michael Viamari commented on KAFKA-12925:
-----------------------------------------
I can flesh out a larger example if needed, but the basic usage for me was
getting a reference to the state store using {{context.getStateStore()}} inside
{{Transformer#init}}, and then when attempting to use
{{TimestampedKeyValueStore#prefixScan}}, the exception was thrown.
{code:java}
public class TransformerPrefixScan<K, V, KS, VS> implements Transformer<K, V,
KeyValue<K, V>> {
private ProcessorContext context;
private TimestampedKeyValueStore<KS, VS> lookupStore;
public TransformerPrefixScan() {}
@Override
@SuppressWarnings("unchecked")
public void init(ProcessorContext context) {
this.context = context;
lookupStore = context.getStateStore(lookupStoreName);
}
@Override
public KeyValue<K, V> transform(K key, V value) {
String keyPrefix = extractPrefix(key);
try (KeyValueIterator<KS, ValueAndTimestamp<VS>> lookupIterator =
lookupStore.prefixScan(keyPrefix, Serdes.String())) {
//....handle results....
}
return null;
}
@Override
public void close() {
}
}
{code}
> prefixScan missing from intermediate interfaces
> -----------------------------------------------
>
> Key: KAFKA-12925
> URL: https://issues.apache.org/jira/browse/KAFKA-12925
> Project: Kafka
> Issue Type: Bug
> Components: streams
> Affects Versions: 2.8.0
> Reporter: Michael Viamari
> Assignee: Sagar Rao
> Priority: Major
> Fix For: 3.0.0, 2.8.1
>
>
> [KIP-614|https://cwiki.apache.org/confluence/display/KAFKA/KIP-614%3A+Add+Prefix+Scan+support+for+State+Stores]
> and [KAFKA-10648|https://issues.apache.org/jira/browse/KAFKA-10648]
> introduced support for {{prefixScan}} to StateStores.
> It seems that many of the intermediate {{StateStore}} interfaces are missing
> a definition for {{prefixScan}}, and as such is not accessible in all cases.
> For example, when accessing the state stores through a the processor context,
> the {{KeyValueStoreReadWriteDecorator}} and associated interfaces do not
> define {{prefixScan}} and it falls back to the default implementation in
> {{KeyValueStore}}, which throws {{UnsupportedOperationException}}.
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