leventov commented on a change in pull request #4551: Fixes and improvements to
SQL metadata caching.
URL: https://github.com/apache/incubator-druid/pull/4551#discussion_r247866248
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File path: sql/src/main/java/io/druid/sql/calcite/schema/DruidSchema.java
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@@ -59,42 +58,66 @@
import io.druid.sql.calcite.view.DruidViewMacro;
import io.druid.sql.calcite.view.ViewManager;
import io.druid.timeline.DataSegment;
-import org.apache.calcite.schema.Function;
import org.apache.calcite.schema.Table;
import org.apache.calcite.schema.impl.AbstractSchema;
import org.joda.time.DateTime;
+import java.io.IOException;
+import java.util.Comparator;
import java.util.EnumSet;
-import java.util.List;
+import java.util.HashMap;
+import java.util.HashSet;
import java.util.Map;
import java.util.Set;
+import java.util.TreeMap;
+import java.util.TreeSet;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+import java.util.stream.StreamSupport;
@ManageLifecycle
public class DruidSchema extends AbstractSchema
{
+ // Newest segments first, so they override older ones.
Review comment:
The latter may not improve performance, but be necessary for #6827, because
`segmentMetadataInfo` may need to become `ConcurrentHashMap<String,
ConcurrentHashMap<DataSegment, SegmentMetadataHolder>>` to enable safe
iteration concurrent with modification. Assuming that we want to avoid
`ConcurrentSkipListMap` because it's not memory efficient and slow.
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