nicktelford commented on code in PR #22682:
URL: https://github.com/apache/kafka/pull/22682#discussion_r3491368537
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streams/src/main/java/org/apache/kafka/streams/state/internals/LogicalKeyValueSegment.java:
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@@ -60,26 +61,53 @@ public class LogicalKeyValueSegment implements Segment,
VersionedStoreSegment {
private final String name;
private final RocksDBStore physicalStore;
private final PrefixKeyFormatter prefixKeyFormatter;
+ // Non-null for read-only views produced by {@link
#readOnly(IsolationLevel)}: all reads go
+ // through this accessor (bypassing any transaction buffer for
READ_COMMITTED); writes are
+ // disallowed. Null for regular segments, which use the physicalStore's
current accessor.
+ private final RocksDBStore.DBAccessor readAccessor;
final Set<KeyValueIterator<Bytes, byte[]>> openIterators =
Collections.synchronizedSet(new HashSet<>());
LogicalKeyValueSegment(final long id,
final String name,
final RocksDBStore physicalStore) {
+ this(id, name, physicalStore, null);
+ }
+
+ private LogicalKeyValueSegment(final long id,
+ final String name,
+ final RocksDBStore physicalStore,
+ final RocksDBStore.DBAccessor readAccessor)
{
this.id = id;
this.name = name;
this.physicalStore = Objects.requireNonNull(physicalStore);
-
+ this.readAccessor = readAccessor;
this.prefixKeyFormatter = new
PrefixKeyFormatter(serializeLongToBytes(id));
}
+ /**
+ * Returns a read-only view of this segment bound to the given isolation
level. Reads go
+ * through the accessor appropriate for {@code level}; mutating calls
throw.
+ */
+ @Override
+ public LogicalKeyValueSegment readOnly(final IsolationLevel level) {
+ return new LogicalKeyValueSegment(id, name, physicalStore,
physicalStore.viewAccessor(level));
+ }
+
+ private void rejectIfReadOnly() {
+ if (readAccessor != null) {
+ throw new UnsupportedOperationException("Write operations are not
supported on a read-only segment view");
+ }
+ }
+
@Override
public long id() {
return id;
}
@Override
public synchronized void destroy() {
Review Comment:
`destroy` isn't called by Interactive Queries or read-only views, so it
shouldn't be an issue. Unless that's not what you were asking?
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