leventov commented on a change in pull request #8157: Enum of ResponseContext
keys
URL: https://github.com/apache/incubator-druid/pull/8157#discussion_r308780090
##########
File path:
processing/src/main/java/org/apache/druid/query/context/ResponseContext.java
##########
@@ -44,9 +47,47 @@
public abstract class ResponseContext
{
/**
- * Keys associated with objects in the context.
+ * The base interface of a response context key.
+ * Should be implemented by every context key.
*/
- public enum Key
+ public interface BaseKey
+ {
+ String getName();
+ /**
+ * Merge function associated with a key: Object (Object oldValue, Object
newValue)
+ */
+ BiFunction<Object, Object, Object> getMergeFunction();
+ }
+
+ /**
+ * Keys associated with objects in the context. The enum is
extension-friendly.
+ * <p>If it's necessary to have some new keys in the context then they could
be described in a separate enum:
+ * <pre>{@code
+ * public enum ExtensionResponseContextKey implements BaseKey
+ * {
+ * EXTENSION_KEY_1("extension_key_1"), EXTENSION_KEY_2("extension_key_2");
+ *
+ * static {
+ * for (ResponseContextKey key : values())
ResponseContext.Key.addKey(key);
+ * }
+ *
+ * private final String name;
+ * private final BiFunction<Object, Object, Object> mergeFunction;
+ *
+ * ExtensionResponseContextKey(String name)
+ * {
+ * this.name = name;
+ * this.mergeFunction = (oldValue, newValue) -> newValue;
+ * }
+ *
+ * @Override public String getName() { return name; }
+ *
+ * @Override public BiFunction<Object, Object, Object> getMergeFunction()
{ return mergeFunction; }
+ * }
+ * }</pre>
+ * Make sure all extension enum values added with Key.addKey method.
Review comment:
Please make `Key.addKey` a `{@link }`
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