leventov commented on a change in pull request #8157: Enum of ResponseContext
keys
URL: https://github.com/apache/incubator-druid/pull/8157#discussion_r310215079
##########
File path:
processing/src/main/java/org/apache/druid/query/context/ResponseContext.java
##########
@@ -19,53 +19,236 @@
package org.apache.druid.query.context;
+import com.fasterxml.jackson.annotation.JsonValue;
import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.node.ArrayNode;
+import com.fasterxml.jackson.databind.node.ObjectNode;
+import com.google.common.base.Preconditions;
+import com.google.common.collect.Lists;
import org.apache.druid.guice.annotations.PublicApi;
import org.apache.druid.java.util.common.jackson.JacksonUtils;
+import org.apache.druid.query.SegmentDescriptor;
+import org.joda.time.Interval;
import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
import java.util.Map;
+import java.util.TreeMap;
+import java.util.function.BiFunction;
/**
* The context for storing and passing data between chains of {@link
org.apache.druid.query.QueryRunner}s.
* The context is also transferred between Druid nodes with all the data it
contains.
- * All the keys associated with data inside the context should be stored here.
- * CTX_* keys might be aggregated into an enum. Consider refactoring that.
*/
@PublicApi
public abstract class ResponseContext
{
/**
- * Lists intervals for which NO segment is present.
+ * The base interface of a response context key.
+ * Should be implemented by every context key.
*/
- public static final String CTX_UNCOVERED_INTERVALS = "uncoveredIntervals";
- /**
- * Indicates if the number of uncovered intervals exceeded the limit
(true/false).
- */
- public static final String CTX_UNCOVERED_INTERVALS_OVERFLOWED =
"uncoveredIntervalsOverflowed";
- /**
- * Lists missing segments.
- */
- public static final String CTX_MISSING_SEGMENTS = "missingSegments";
- /**
- * Entity tag. A part of HTTP cache validation mechanism.
- * Is being removed from the context before sending and used as a separate
HTTP header.
- */
- public static final String CTX_ETAG = "ETag";
- /**
- * Query total bytes gathered.
- */
- public static final String CTX_QUERY_TOTAL_BYTES_GATHERED =
"queryTotalBytesGathered";
- /**
- * This variable indicates when a running query should be expired,
- * and is effective only when 'timeout' of queryContext has a positive value.
- */
- public static final String CTX_TIMEOUT_AT = "timeoutAt";
+ public interface BaseKey
+ {
+ @JsonValue
+ String getName();
+ /**
+ * Merge function associated with a key: Object (Object oldValue, Object
newValue)
+ */
+ BiFunction<Object, Object, Object> getMergeFunction();
+ }
+
/**
- * The number of scanned rows.
+ * Keys associated with objects in the context.
+ * <p>
+ * If it's necessary to have some new keys in the context then they might be
listed 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 (BaseKey key : values()) ResponseContext.Key.registerKey(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 {@link Key#registerKey}
method.
*/
- public static final String CTX_COUNT = "count";
+ public enum Key implements BaseKey
+ {
+ /**
+ * Lists intervals for which NO segment is present.
+ */
+ UNCOVERED_INTERVALS(
+ "uncoveredIntervals",
+ (oldValue, newValue) -> {
+ final ArrayList<Interval> result = new
ArrayList<Interval>((List) oldValue);
+ result.addAll((List) newValue);
+ return result;
+ }
+ ),
+ /**
+ * Indicates if the number of uncovered intervals exceeded the limit
(true/false).
+ */
+ UNCOVERED_INTERVALS_OVERFLOWED(
+ "uncoveredIntervalsOverflowed",
+ (oldValue, newValue) -> (boolean) oldValue || (boolean) newValue
+ ),
+ /**
+ * Lists missing segments.
+ */
+ MISSING_SEGMENTS(
+ "missingSegments",
+ (oldValue, newValue) -> {
+ final ArrayList<SegmentDescriptor> result = new
ArrayList<SegmentDescriptor>((List) oldValue);
+ result.addAll((List) newValue);
+ return result;
+ }
+ ),
+ /**
+ * Entity tag. A part of HTTP cache validation mechanism.
+ * Is being removed from the context before sending and used as a separate
HTTP header.
+ */
+ ETAG("ETag"),
+ /**
+ * Query fail time (current time + timeout).
+ * It is not updated continuously as TIMEOUT_AT.
Review comment:
Please wrap `TIMEOUT_AT` with `{@link }`.
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