Avoid dynamic ArrayList growth in HitGroup when number of hits is known

6 files changed, 149 insertions, 135 deletions

diff --git a/container-search/abi-spec.json b/container-search/abi-spec.json
index b968d1c391f..fb50da7bff1 100644
--- a/container-search/abi-spec.json
+++ b/container-search/abi-spec.json
@@ -7252,6 +7252,7 @@
       "public void setId(com.yahoo.net.URI)",
       "public void setOrdered(boolean)",
       "public int size()",
+      "public void ensureCapacity(int)",
       "public int getConcreteSize()",
       "public int getConcreteSizeShallow()",
       "public int getSubgroupCount()",
diff --git a/container-search/src/main/java/com/yahoo/prelude/fastsearch/FS4FillInvoker.java b/container-search/src/main/java/com/yahoo/prelude/fastsearch/FS4FillInvoker.java
index 190a7905476..5dc213a6120 100644
--- a/container-search/src/main/java/com/yahoo/prelude/fastsearch/FS4FillInvoker.java
+++ b/container-search/src/main/java/com/yahoo/prelude/fastsearch/FS4FillInvoker.java
@@ -9,6 +9,7 @@ import com.yahoo.fs4.mplex.Backend;
 import com.yahoo.fs4.mplex.FS4Channel;
 import com.yahoo.fs4.mplex.InvalidChannelException;
 import com.yahoo.prelude.fastsearch.VespaBackEndSearcher.FillHitsResult;
+import com.yahoo.processing.request.CompoundName;
 import com.yahoo.search.Query;
 import com.yahoo.search.Result;
 import com.yahoo.search.dispatch.FillInvoker;
@@ -26,7 +27,6 @@ import static com.yahoo.prelude.fastsearch.VespaBackEndSearcher.hitIterator;
  * @author ollivir
  */
 public class FS4FillInvoker extends FillInvoker {
-
     private final VespaBackEndSearcher searcher;
     private FS4Channel channel;
 
@@ -156,10 +156,10 @@ public class FS4FillInvoker extends FillInvoker {
             result.getQuery().trace((summaryNeedsQuery ? "Resending " : "Not resending ") + "query during document summary fetching", 3);
 
         GetDocSumsPacket docsumsPacket = GetDocSumsPacket.create(result, summaryClass, summaryNeedsQuery);
-        int compressionLimit = result.getQuery().properties().getInteger(FastSearcher.PACKET_COMPRESSION_LIMIT, 0);
+        int compressionLimit = result.getQuery().properties().getInteger(FS4SearchInvoker.PACKET_COMPRESSION_LIMIT, 0);
         docsumsPacket.setCompressionLimit(compressionLimit);
         if (compressionLimit != 0) {
-            docsumsPacket.setCompressionType(result.getQuery().properties().getString(FastSearcher.PACKET_COMPRESSION_TYPE, "lz4"));
+            docsumsPacket.setCompressionType(result.getQuery().properties().getString(FS4SearchInvoker.PACKET_COMPRESSION_TYPE, "lz4"));
         }
 
         boolean couldSend = channel.sendPacket(docsumsPacket);
diff --git a/container-search/src/main/java/com/yahoo/prelude/fastsearch/FS4SearchInvoker.java b/container-search/src/main/java/com/yahoo/prelude/fastsearch/FS4SearchInvoker.java
index 2353054103d..27c4c73dd65 100644
--- a/container-search/src/main/java/com/yahoo/prelude/fastsearch/FS4SearchInvoker.java
+++ b/container-search/src/main/java/com/yahoo/prelude/fastsearch/FS4SearchInvoker.java
@@ -1,21 +1,39 @@
 // Copyright 2018 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.prelude.fastsearch;
 
+import com.yahoo.data.access.simple.Value;
+import com.yahoo.data.access.slime.SlimeAdapter;
 import com.yahoo.fs4.BasicPacket;
 import com.yahoo.fs4.ChannelTimeoutException;
+import com.yahoo.fs4.DocumentInfo;
+import com.yahoo.fs4.FS4Properties;
 import com.yahoo.fs4.QueryPacket;
+import com.yahoo.fs4.QueryPacketData;
 import com.yahoo.fs4.QueryResultPacket;
 import com.yahoo.fs4.mplex.FS4Channel;
 import com.yahoo.fs4.mplex.InvalidChannelException;
+import com.yahoo.io.GrowableByteBuffer;
+import com.yahoo.log.LogLevel;
+import com.yahoo.prelude.ConfigurationException;
+import com.yahoo.processing.request.CompoundName;
 import com.yahoo.search.Query;
 import com.yahoo.search.Result;
 import com.yahoo.search.dispatch.ResponseMonitor;
 import com.yahoo.search.dispatch.SearchInvoker;
 import com.yahoo.search.dispatch.searchcluster.Node;
+import com.yahoo.search.query.Sorting;
+import com.yahoo.search.result.Coverage;
 import com.yahoo.search.result.ErrorMessage;
+import com.yahoo.search.result.Relevance;
 import com.yahoo.search.searchchain.Execution;
+import com.yahoo.searchlib.aggregation.Grouping;
+import com.yahoo.slime.BinaryFormat;
+import com.yahoo.vespa.objects.BufferSerializer;
 
 import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.util.ArrayList;
+import java.util.List;
 import java.util.Optional;
 import java.util.logging.Logger;
 
@@ -25,6 +43,9 @@ import java.util.logging.Logger;
  * @author ollivir
  */
 public class FS4SearchInvoker extends SearchInvoker implements ResponseMonitor<FS4Channel> {
+    static final CompoundName PACKET_COMPRESSION_LIMIT = new CompoundName("packetcompressionlimit");
+    static final CompoundName PACKET_COMPRESSION_TYPE = new CompoundName("packetcompressiontype");
+
     private static final Logger log = Logger.getLogger(FS4SearchInvoker.class.getName());
 
     private final VespaBackEndSearcher searcher;
@@ -48,7 +69,7 @@ public class FS4SearchInvoker extends SearchInvoker implements ResponseMonitor<F
         log.finest("sending query packet");
 
         this.query = query;
-        this.queryPacket = searcher.createQueryPacket(searcher.getServerId(), query);
+        createQueryPacket(searcher.getServerId(), query);
 
         try {
             boolean couldSend = channel.sendPacket(queryPacket);
@@ -98,13 +119,120 @@ public class FS4SearchInvoker extends SearchInvoker implements ResponseMonitor<F
 
         Result result = new Result(query);
 
-        searcher.addMetaInfo(query, queryPacket.getQueryPacketData(), resultPacket, result);
-
-        searcher.addUnfilledHits(result, resultPacket.getDocuments(), queryPacket.getQueryPacketData(), distributionKey());
+        ensureResultHitCapacity(result, resultPacket);
+        addMetaInfo(query, queryPacket.getQueryPacketData(), resultPacket, result);
+        addUnfilledHits(result, resultPacket.getDocuments(), queryPacket.getQueryPacketData());
 
         return result;
     }
 
+    private QueryPacket createQueryPacket(String serverId, Query query) {
+        this.queryPacket = QueryPacket.create(serverId, query);
+        int compressionLimit = query.properties().getInteger(PACKET_COMPRESSION_LIMIT, 0);
+        queryPacket.setCompressionLimit(compressionLimit);
+        if (compressionLimit != 0) {
+            queryPacket.setCompressionType(query.properties().getString(PACKET_COMPRESSION_TYPE, "lz4"));
+        }
+        log.fine(() -> "made QueryPacket: " + queryPacket);
+
+        return queryPacket;
+    }
+
+    private void ensureResultHitCapacity(Result result, QueryResultPacket resultPacket) {
+        int hitCount = resultPacket.getDocumentCount();
+        if (resultPacket.getGroupData() != null) {
+            hitCount++;
+        }
+        result.hits().ensureCapacity(hitCount);
+    }
+
+    private void addMetaInfo(Query query, QueryPacketData queryPacketData, QueryResultPacket resultPacket, Result result) {
+        result.setTotalHitCount(resultPacket.getTotalDocumentCount());
+
+        addBackendTrace(query, resultPacket);
+
+        // Grouping
+        if (resultPacket.getGroupData() != null) {
+            byte[] data = resultPacket.getGroupData();
+            ArrayList<Grouping> list = new ArrayList<>();
+            BufferSerializer buf = new BufferSerializer(new GrowableByteBuffer(ByteBuffer.wrap(data)));
+            int cnt = buf.getInt(null);
+            for (int i = 0; i < cnt; i++) {
+                Grouping g = new Grouping();
+                g.deserialize(buf);
+                list.add(g);
+            }
+            GroupingListHit hit = new GroupingListHit(list, searcher.getDocsumDefinitionSet(query));
+            hit.setQuery(result.getQuery());
+            hit.setSource(getName());
+            hit.setQueryPacketData(queryPacketData);
+            result.hits().add(hit);
+        }
+
+        if (resultPacket.getCoverageFeature()) {
+            result.setCoverage(new Coverage(resultPacket.getCoverageDocs(), resultPacket.getActiveDocs(), resultPacket.getNodesReplied())
+                    .setSoonActive(resultPacket.getSoonActiveDocs())
+                    .setDegradedReason(resultPacket.getDegradedReason())
+                    .setNodesTried(resultPacket.getNodesQueried()));
+        }
+    }
+
+    private void addBackendTrace(Query query, QueryResultPacket resultPacket) {
+        if (resultPacket.propsArray == null) return;
+        Value.ArrayValue traces = new Value.ArrayValue();
+        for (FS4Properties properties : resultPacket.propsArray) {
+            if ( ! properties.getName().equals("trace")) continue;
+            for (FS4Properties.Entry entry : properties.getEntries()) {
+                traces.add(new SlimeAdapter(BinaryFormat.decode(entry.getValue()).get()));
+            }
+        }
+        query.trace(traces, query.getTraceLevel());
+    }
+
+    /**
+     * Creates unfilled hits from a List of DocumentInfo instances.
+     */
+    private void addUnfilledHits(Result result, List<DocumentInfo> documents, QueryPacketData queryPacketData) {
+        Query myQuery = result.getQuery();
+        Sorting sorting = myQuery.getRanking().getSorting();
+        Optional<Integer> channelDistributionKey = distributionKey();
+
+        for (DocumentInfo document : documents) {
+
+            try {
+                FastHit hit = new FastHit();
+                hit.setQuery(myQuery);
+                if (queryPacketData != null)
+                    hit.setQueryPacketData(queryPacketData);
+
+                hit.setFillable();
+                hit.setCached(false);
+
+                extractDocumentInfo(hit, document, sorting);
+                channelDistributionKey.ifPresent(hit::setDistributionKey);
+
+                result.hits().add(hit);
+            } catch (ConfigurationException e) {
+                log.log(LogLevel.WARNING, "Skipping hit", e);
+            } catch (Exception e) {
+                log.log(LogLevel.ERROR, "Skipping malformed hit", e);
+            }
+        }
+    }
+
+    private void extractDocumentInfo(FastHit hit, DocumentInfo document, Sorting sorting) {
+        hit.setSource(getName());
+
+        Number rank = document.getMetric();
+
+        hit.setRelevance(new Relevance(rank.doubleValue()));
+
+        hit.setDistributionKey(document.getDistributionKey());
+        hit.setGlobalId(document.getGlobalId());
+        hit.setPartId(document.getPartId());
+        hit.setSortData(document.getSortData(), sorting);
+    }
+
     @Override
     public void release() {
         if (channel != null) {
diff --git a/container-search/src/main/java/com/yahoo/prelude/fastsearch/VespaBackEndSearcher.java b/container-search/src/main/java/com/yahoo/prelude/fastsearch/VespaBackEndSearcher.java
index f5e437c2410..055b41fd89d 100644
--- a/container-search/src/main/java/com/yahoo/prelude/fastsearch/VespaBackEndSearcher.java
+++ b/container-search/src/main/java/com/yahoo/prelude/fastsearch/VespaBackEndSearcher.java
@@ -2,18 +2,9 @@
 package com.yahoo.prelude.fastsearch;
 
 import com.yahoo.collections.TinyIdentitySet;
-import com.yahoo.data.access.simple.Value;
-import com.yahoo.data.access.slime.SlimeAdapter;
 import com.yahoo.fs4.DocsumPacket;
-import com.yahoo.fs4.DocumentInfo;
-import com.yahoo.fs4.FS4Properties;
 import com.yahoo.fs4.Packet;
 import com.yahoo.fs4.QueryPacket;
-import com.yahoo.fs4.QueryPacketData;
-import com.yahoo.fs4.QueryResultPacket;
-import com.yahoo.io.GrowableByteBuffer;
-import com.yahoo.log.LogLevel;
-import com.yahoo.prelude.ConfigurationException;
 import com.yahoo.prelude.query.Item;
 import com.yahoo.prelude.query.NullItem;
 import com.yahoo.prelude.query.textualrepresentation.TextualQueryRepresentation;
@@ -24,20 +15,14 @@ import com.yahoo.search.Query;
 import com.yahoo.search.Result;
 import com.yahoo.search.cluster.PingableSearcher;
 import com.yahoo.search.grouping.vespa.GroupingExecutor;
-import com.yahoo.search.query.Sorting;
-import com.yahoo.search.result.Coverage;
 import com.yahoo.search.result.ErrorHit;
 import com.yahoo.search.result.ErrorMessage;
 import com.yahoo.search.result.Hit;
-import com.yahoo.search.result.Relevance;
 import com.yahoo.search.searchchain.Execution;
 import com.yahoo.searchlib.aggregation.Grouping;
-import com.yahoo.slime.BinaryFormat;
-import com.yahoo.vespa.objects.BufferSerializer;
 
 import java.io.IOException;
 import java.lang.reflect.Constructor;
-import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.LinkedHashMap;
@@ -55,8 +40,6 @@ import java.util.logging.Logger;
  */
 public abstract class VespaBackEndSearcher extends PingableSearcher {
 
-    static final CompoundName PACKET_COMPRESSION_LIMIT = new CompoundName("packetcompressionlimit");
-    static final CompoundName PACKET_COMPRESSION_TYPE = new CompoundName("packetcompressiontype");
     private static final CompoundName TRACE_DISABLE = new CompoundName("trace.disable");
 
     private String serverId;
@@ -198,19 +181,6 @@ public abstract class VespaBackEndSearcher extends PingableSearcher {
         return result;
     }
 
-    protected QueryPacket createQueryPacket(String serverId, Query query) {
-        QueryPacket queryPacket = QueryPacket.create(serverId, query);
-        int compressionLimit = query.properties().getInteger(PACKET_COMPRESSION_LIMIT, 0);
-        queryPacket.setCompressionLimit(compressionLimit);
-        if (compressionLimit != 0)
-            queryPacket.setCompressionType(query.properties().getString(PACKET_COMPRESSION_TYPE, "lz4"));
-
-        if (isLoggingFine())
-            getLogger().fine("made QueryPacket: " + queryPacket);
-
-        return queryPacket;
-    }
-
     private List<Result> partitionHits(Result result, String summaryClass) {
         List<Result> parts = new ArrayList<>();
         TinyIdentitySet<Query> queryMap = new TinyIdentitySet<>(4);
@@ -343,49 +313,6 @@ public abstract class VespaBackEndSearcher extends PingableSearcher {
         }
     }
 
-    private void addBackendTrace(Query query, QueryResultPacket resultPacket) {
-        if (resultPacket.propsArray == null) return;
-        Value.ArrayValue traces = new Value.ArrayValue();
-        for (FS4Properties properties : resultPacket.propsArray) {
-            if ( ! properties.getName().equals("trace")) continue;
-            for (FS4Properties.Entry entry : properties.getEntries()) {
-                traces.add(new SlimeAdapter(BinaryFormat.decode(entry.getValue()).get()));
-            }
-        }
-        query.trace(traces, query.getTraceLevel());
-    }
-
-    void addMetaInfo(Query query, QueryPacketData queryPacketData, QueryResultPacket resultPacket, Result result) {
-        result.setTotalHitCount(resultPacket.getTotalDocumentCount());
-
-        addBackendTrace(query, resultPacket);
-
-        // Grouping
-        if (resultPacket.getGroupData() != null) {
-            byte[] data = resultPacket.getGroupData();
-            ArrayList<Grouping> list = new ArrayList<>();
-            BufferSerializer buf = new BufferSerializer(new GrowableByteBuffer(ByteBuffer.wrap(data)));
-            int cnt = buf.getInt(null);
-            for (int i = 0; i < cnt; i++) {
-                Grouping g = new Grouping();
-                g.deserialize(buf);
-                list.add(g);
-            }
-            GroupingListHit hit = new GroupingListHit(list, getDocsumDefinitionSet(query));
-            hit.setQuery(result.getQuery());
-            hit.setSource(getName());
-            hit.setQueryPacketData(queryPacketData);
-            result.hits().add(hit);
-        }
-
-        if (resultPacket.getCoverageFeature()) {
-            result.setCoverage(new Coverage(resultPacket.getCoverageDocs(), resultPacket.getActiveDocs(), resultPacket.getNodesReplied())
-                    .setSoonActive(resultPacket.getSoonActiveDocs())
-                    .setDegradedReason(resultPacket.getDegradedReason())
-                    .setNodesTried(resultPacket.getNodesQueried()));
-        }
-    }
-
     static class FillHitResult {
         final boolean ok;
         final String error;
@@ -451,19 +378,6 @@ public abstract class VespaBackEndSearcher extends PingableSearcher {
         return new FillHitsResult(skippedHits, lastError);
     }
 
-    private void extractDocumentInfo(FastHit hit, DocumentInfo document, Sorting sorting) {
-        hit.setSource(getName());
-
-        Number rank = document.getMetric();
-
-        hit.setRelevance(new Relevance(rank.doubleValue()));
-
-        hit.setDistributionKey(document.getDistributionKey());
-        hit.setGlobalId(document.getGlobalId());
-        hit.setPartId(document.getPartId());
-        hit.setSortData(document.getSortData(), sorting);
-    }
-
     protected DocsumDefinitionSet getDocsumDefinitionSet(Query query) {
         DocumentDatabase db = getDocumentDatabase(query);
         return db.getDocsumDefinitionSet();
@@ -483,46 +397,6 @@ public abstract class VespaBackEndSearcher extends PingableSearcher {
         return error;
     }
 
-    /**
-     * Creates unfilled hits from a List of DocumentInfo instances. Do note
-     * cacheKey should be available if a cache is active, even if the hit is not
-     * created from a cache in the current call path.
-     *
-     * @param queryPacketData binary data from first phase of search, or null
-     * @param channelDistributionKey distribution key of the node producing these hits.
-     *                               Only set if produced directly by a search node, not dispatch
-     *                               (in which case it is not set in the received packets.)
-     */
-    void addUnfilledHits(Result result,
-                            List<DocumentInfo> documents,
-                            QueryPacketData queryPacketData,
-                            Optional<Integer> channelDistributionKey) {
-        Query myQuery = result.getQuery();
-        Sorting sorting = myQuery.getRanking().getSorting();
-
-        for (DocumentInfo document : documents) {
-
-            try {
-                FastHit hit = new FastHit();
-                hit.setQuery(myQuery);
-                if (queryPacketData != null)
-                    hit.setQueryPacketData(queryPacketData);
-
-                hit.setFillable();
-                hit.setCached(false);
-
-                extractDocumentInfo(hit, document, sorting);
-                channelDistributionKey.ifPresent(hit::setDistributionKey);
-
-                result.hits().add(hit);
-            } catch (ConfigurationException e) {
-                getLogger().log(LogLevel.WARNING, "Skipping hit", e);
-            } catch (Exception e) {
-                getLogger().log(LogLevel.ERROR, "Skipping malformed hit", e);
-            }
-        }
-    }
-
     @SuppressWarnings("rawtypes")
     public static VespaBackEndSearcher getSearcher(String s) {
         try {
diff --git a/container-search/src/main/java/com/yahoo/search/dispatch/rpc/ProtobufSerialization.java b/container-search/src/main/java/com/yahoo/search/dispatch/rpc/ProtobufSerialization.java
index 033b507b4a4..76da9fbc1f7 100644
--- a/container-search/src/main/java/com/yahoo/search/dispatch/rpc/ProtobufSerialization.java
+++ b/container-search/src/main/java/com/yahoo/search/dispatch/rpc/ProtobufSerialization.java
@@ -168,10 +168,17 @@ public class ProtobufSerialization {
         result.setTotalHitCount(protobuf.getTotalHitCount());
         result.setCoverage(convertToCoverage(protobuf));
 
-        if (protobuf.getGroupingBlob() != null && !protobuf.getGroupingBlob().isEmpty()) {
-            ArrayList<Grouping> list = new ArrayList<>();
+        int hitItems = protobuf.getHitsCount();
+        var haveGrouping = protobuf.getGroupingBlob() != null && !protobuf.getGroupingBlob().isEmpty();
+        if(haveGrouping) {
+            hitItems++;
+        }
+        result.hits().ensureCapacity(hitItems);
+
+        if (haveGrouping) {
             BufferSerializer buf = new BufferSerializer(new GrowableByteBuffer(protobuf.getGroupingBlob().asReadOnlyByteBuffer()));
             int cnt = buf.getInt(null);
+            ArrayList<Grouping> list = new ArrayList<>(cnt);
             for (int i = 0; i < cnt; i++) {
                 Grouping g = new Grouping();
                 g.deserialize(buf);
diff --git a/container-search/src/main/java/com/yahoo/search/result/HitGroup.java b/container-search/src/main/java/com/yahoo/search/result/HitGroup.java
index 8755d0b0897..9ecd6513a94 100644
--- a/container-search/src/main/java/com/yahoo/search/result/HitGroup.java
+++ b/container-search/src/main/java/com/yahoo/search/result/HitGroup.java
@@ -191,6 +191,10 @@ public class HitGroup extends Hit implements DataList<Hit>, Cloneable, Iterable<
         return hits.size();
     }
 
+    public void ensureCapacity(int minCapacity) {
+        hits.ensureCapacity(minCapacity);
+    }
+
     /**
      * <p>Returns the number of concrete hits contained in this group
      * and all subgroups. This should equal the