iamaleksey commented on code in PR #2982:
URL: https://github.com/apache/cassandra/pull/2982#discussion_r1450540304
##########
src/java/org/apache/cassandra/journal/Segments.java:
##########
@@ -17,123 +17,92 @@
*/
package org.apache.cassandra.journal;
-import java.util.ArrayList;
import java.util.Collection;
-import java.util.Collections;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-
-import com.google.common.collect.Iterables;
-import com.google.common.collect.Maps;
import accord.utils.Invariants;
+import org.agrona.collections.Long2ObjectHashMap;
+import org.apache.cassandra.utils.concurrent.Ref;
import org.apache.cassandra.utils.concurrent.Refs;
-import static java.util.Collections.emptyList;
-import static java.util.Collections.emptyMap;
-
/**
* Consistent, immutable view of active + static segments
* <p/>
- * TODO: an interval/range structure for StaticSegment lookup based on min/max
key bounds
+ * TODO (performance, expected): an interval/range structure for StaticSegment
lookup based on min/max key bounds
*/
-class Segments<K>
+class Segments<K, V>
{
- // active segments, containing unflushed data; the tail of this queue is
the one we allocate writes from
- private final List<ActiveSegment<K>> activeSegments;
-
- // finalised segments, no longer written to
- private final Map<Descriptor, StaticSegment<K>> staticSegments;
+ private final Long2ObjectHashMap<Segment<K, V>> segments;
- // cached Iterable of concatenated active and static segments
- private final Iterable<Segment<K>> allSegments;
-
- Segments(List<ActiveSegment<K>> activeSegments, Map<Descriptor,
StaticSegment<K>> staticSegments)
+ Segments(Long2ObjectHashMap<Segment<K, V>> segments)
{
- this.activeSegments = activeSegments;
- this.staticSegments = staticSegments;
- this.allSegments = Iterables.concat(onlyActive(), onlyStatic());
+ this.segments = segments;
}
- static <K> Segments<K> ofStatic(Collection<StaticSegment<K>> segments)
+ static <K, V> Segments<K, V> of(Collection<Segment<K, V>> segments)
{
- HashMap<Descriptor, StaticSegment<K>> staticSegments =
- Maps.newHashMapWithExpectedSize(segments.size());
- for (StaticSegment<K> segment : segments)
- staticSegments.put(segment.descriptor, segment);
- return new Segments<>(new ArrayList<>(), staticSegments);
+ Long2ObjectHashMap<Segment<K, V>> newSegments =
newMap(segments.size());
+ for (Segment<K, V> segment : segments)
+ newSegments.put(segment.descriptor.timestamp, segment);
+ return new Segments<>(newSegments);
}
- static <K> Segments<K> none()
+ static <K, V> Segments<K, V> none()
{
- return new Segments<>(Collections.emptyList(), Collections.emptyMap());
+ return new Segments<>(emptyMap());
}
- Segments<K> withNewActiveSegment(ActiveSegment<K> activeSegment)
+ Segments<K, V> withNewActiveSegment(ActiveSegment<K, V> activeSegment)
{
- ArrayList<ActiveSegment<K>> newActiveSegments =
- new ArrayList<>(activeSegments.size() + 1);
- newActiveSegments.addAll(activeSegments);
- newActiveSegments.add(activeSegment);
- return new Segments<>(newActiveSegments, staticSegments);
+ Long2ObjectHashMap<Segment<K, V>> newSegments = new
Long2ObjectHashMap<>(segments);
+ Segment<K, V> oldValue =
newSegments.put(activeSegment.descriptor.timestamp, activeSegment);
+ Invariants.checkState(oldValue == null);
+ return new Segments<>(newSegments);
}
- Segments<K> withCompletedSegment(ActiveSegment<K> activeSegment,
StaticSegment<K> staticSegment)
+ Segments<K, V> withCompletedSegment(ActiveSegment<K, V> activeSegment,
StaticSegment<K, V> staticSegment)
{
Invariants.checkArgument(activeSegment.descriptor.equals(staticSegment.descriptor));
-
- ArrayList<ActiveSegment<K>> newActiveSegments =
- new ArrayList<>(activeSegments.size() - 1);
- for (ActiveSegment<K> segment : activeSegments)
- if (segment != activeSegment)
- newActiveSegments.add(segment);
- Invariants.checkState(newActiveSegments.size() ==
activeSegments.size() - 1);
-
- HashMap<Descriptor, StaticSegment<K>> newStaticSegments =
- Maps.newHashMapWithExpectedSize(staticSegments.size() + 1);
- newStaticSegments.putAll(staticSegments);
- if (newStaticSegments.put(staticSegment.descriptor, staticSegment) !=
null)
- throw new IllegalStateException();
-
- return new Segments<>(newActiveSegments, newStaticSegments);
+ Long2ObjectHashMap<Segment<K, V>> newSegments = new
Long2ObjectHashMap<>(segments);
+ Segment<K, V> oldValue =
newSegments.put(staticSegment.descriptor.timestamp, staticSegment);
+ Invariants.checkState(oldValue == activeSegment);
+ return new Segments<>(newSegments);
}
- Segments<K> withCompactedSegment(StaticSegment<K> oldSegment,
StaticSegment<K> newSegment)
+ Segments<K, V> withCompactedSegment(StaticSegment<K, V> oldSegment,
StaticSegment<K, V> newSegment)
{
Invariants.checkArgument(oldSegment.descriptor.timestamp ==
newSegment.descriptor.timestamp);
Invariants.checkArgument(oldSegment.descriptor.generation <
newSegment.descriptor.generation);
-
- HashMap<Descriptor, StaticSegment<K>> newStaticSegments = new
HashMap<>(staticSegments);
- if (!newStaticSegments.remove(oldSegment.descriptor, oldSegment))
- throw new IllegalStateException();
- if (null != newStaticSegments.put(newSegment.descriptor, newSegment))
- throw new IllegalStateException();
-
- return new Segments<>(activeSegments, newStaticSegments);
+ Long2ObjectHashMap<Segment<K, V>> newSegments = new
Long2ObjectHashMap<>(segments);
+ Segment<K, V> oldValue =
newSegments.put(newSegment.descriptor.timestamp, newSegment);
+ Invariants.checkState(oldValue == oldSegment);
+ return new Segments<>(newSegments);
}
- Segments<K> withoutInvalidatedSegment(StaticSegment<K> staticSegment)
+ Segments<K, V> withoutInvalidatedSegment(StaticSegment<K, V> staticSegment)
{
- HashMap<Descriptor, StaticSegment<K>> newStaticSegments = new
HashMap<>(staticSegments);
- if (!newStaticSegments.remove(staticSegment.descriptor, staticSegment))
+ Long2ObjectHashMap<Segment<K, V>> newSegments = new
Long2ObjectHashMap<>(segments);
+ if (!newSegments.remove(staticSegment.descriptor.timestamp,
staticSegment))
throw new IllegalStateException();
- return new Segments<>(activeSegments, newStaticSegments);
+ return new Segments<>(newSegments);
}
- Iterable<Segment<K>> all()
+ Iterable<Segment<K, V>> all()
{
- return allSegments;
+ return segments.values();
}
- Collection<ActiveSegment<K>> onlyActive()
+ void selectActive(long maxTimestamp, Collection<ActiveSegment<K, V>> into)
Review Comment:
I reuse that list in `Flusher` so as to not generate more garbage than
necessary. I believe it's a good pattern in general, though, for methods like
this to take an input collection - it's something Matin Thompson tends to
advocate for in his talks.
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