Add separate field for exact commit search

Index implementations (including both Lucene and the googlesource.com
index) cannot really implement prefix search efficiently: they need
to iterate over all tokens in the inverted index with a given prefix.
When we have a full commit SHA-1, this indirection is wasteful,
particularly in cases like byCommitsOnBranchNotMerged where there
might be hundreds or thousands of terms.

Add a separate field that indexes the full commit SHA-1 to make these
specific queries more efficient. There is no need for a separate
query operator; we can just choose the predicate based on the length
of the input string.

Change-Id: Ie26d58ab82e9efaf2c32d352cf285a2a1d59a8d8

gerrit-server/src/main/java/com/google/gerrit/server/index/ChangeField.java

@@ -303,22 +303,37 @@ public class ChangeField {
         }
       };
 
-  /** Commit id of any PatchSet on the change */
+  /** Commit ID of any patch set on the change, using prefix match. */
   public static final FieldDef<ChangeData, Iterable<String>> COMMIT =
       new FieldDef.Repeatable<ChangeData, String>(
           ChangeQueryBuilder.FIELD_COMMIT, FieldType.PREFIX, false) {
         @Override
         public Iterable<String> get(ChangeData input, FillArgs args)
             throws OrmException {
+          return getRevisions(input);
+        }
+      };
+
+  /** Commit ID of any patch set on the change, using exact match. */
+  public static final FieldDef<ChangeData, Iterable<String>> EXACT_COMMIT =
+      new FieldDef.Repeatable<ChangeData, String>(
+          "exactcommit", FieldType.EXACT, false) {
+        @Override
+        public Iterable<String> get(ChangeData input, FillArgs args)
+            throws OrmException {
+          return getRevisions(input);
+        }
+      };
+
+  private static Set<String> getRevisions(ChangeData cd) throws OrmException {
     Set<String> revisions = Sets.newHashSet();
-          for (PatchSet ps : input.patchSets()) {
+    for (PatchSet ps : cd.patchSets()) {
       if (ps.getRevision() != null) {
         revisions.add(ps.getRevision().get());
       }
     }
     return revisions;
   }
-      };
 
   /** Tracking id extracted from a footer. */
   public static final FieldDef<ChangeData, Iterable<String>> TR =

gerrit-server/src/main/java/com/google/gerrit/server/index/ChangeSchemas.java

@@ -241,6 +241,7 @@ public class ChangeSchemas {
       ChangeField.EDITBY,
       ChangeField.REVIEWEDBY);
 
+  @Deprecated
   static final Schema<ChangeData> V21 = schema(
       ChangeField.LEGACY_ID,
       ChangeField.ID,
@@ -273,6 +274,40 @@ public class ChangeSchemas {
       ChangeField.EDITBY,
       ChangeField.REVIEWEDBY);
 
+  static final Schema<ChangeData> V22 = schema(
+      ChangeField.LEGACY_ID,
+      ChangeField.ID,
+      ChangeField.STATUS,
+      ChangeField.PROJECT,
+      ChangeField.PROJECTS,
+      ChangeField.REF,
+      ChangeField.EXACT_TOPIC,
+      ChangeField.FUZZY_TOPIC,
+      ChangeField.UPDATED,
+      ChangeField.FILE_PART,
+      ChangeField.PATH,
+      ChangeField.OWNER,
+      ChangeField.REVIEWER,
+      ChangeField.COMMIT,
+      ChangeField.TR,
+      ChangeField.LABEL,
+      ChangeField.COMMIT_MESSAGE,
+      ChangeField.COMMENT,
+      ChangeField.CHANGE,
+      ChangeField.APPROVAL,
+      ChangeField.MERGEABLE,
+      ChangeField.ADDED,
+      ChangeField.DELETED,
+      ChangeField.DELTA,
+      ChangeField.HASHTAG,
+      ChangeField.COMMENTBY,
+      ChangeField.PATCH_SET,
+      ChangeField.GROUP,
+      ChangeField.EDITBY,
+      ChangeField.REVIEWEDBY,
+      ChangeField.EXACT_COMMIT);
+
+
   private static Schema<ChangeData> schema(Collection<FieldDef<ChangeData, ?>> fields) {
     return new Schema<>(ImmutableList.copyOf(fields));
   }

gerrit-server/src/main/java/com/google/gerrit/server/query/change/ChangeQueryBuilder.java

@@ -63,6 +63,8 @@ import org.eclipse.jgit.errors.ConfigInvalidException;
 import org.eclipse.jgit.errors.RepositoryNotFoundException;
 import org.eclipse.jgit.lib.AbbreviatedObjectId;
 import org.eclipse.jgit.lib.Config;
+import org.eclipse.jgit.lib.Constants;
+import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.Repository;
 
 import java.io.IOException;
@@ -431,7 +433,10 @@ public class ChangeQueryBuilder extends QueryBuilder<ChangeData> {
 
   @Operator
   public Predicate<ChangeData> commit(String id) {
-    return new CommitPredicate(AbbreviatedObjectId.fromString(id));
+    if (id.length() == Constants.OBJECT_ID_STRING_LENGTH) {
+      return new ExactCommitPredicate(ObjectId.fromString(id));
+    }
+    return new CommitPrefixPredicate(AbbreviatedObjectId.fromString(id));
   }
 
   @Operator

gerrit-server/src/main/java/com/google/gerrit/server/query/change/CommitPrefixPredicate.java

@@ -22,10 +22,10 @@ import com.google.gwtorm.server.OrmException;
 import org.eclipse.jgit.lib.AbbreviatedObjectId;
 import org.eclipse.jgit.lib.ObjectId;
 
-class CommitPredicate extends IndexPredicate<ChangeData> {
+class CommitPrefixPredicate extends IndexPredicate<ChangeData> {
   private final AbbreviatedObjectId abbrevId;
 
-  CommitPredicate(AbbreviatedObjectId id) {
+  CommitPrefixPredicate(AbbreviatedObjectId id) {
     super(ChangeField.COMMIT, id.name());
     this.abbrevId = id;
   }

gerrit-server/src/main/java/com/google/gerrit/server/query/change/ExactCommitPredicate.java

@@ -0,0 +1,51 @@
+// Copyright (C) 2015 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.server.query.change;
+
+import com.google.gerrit.reviewdb.client.PatchSet;
+import com.google.gerrit.server.index.ChangeField;
+import com.google.gerrit.server.index.IndexPredicate;
+import com.google.gwtorm.server.OrmException;
+
+import org.eclipse.jgit.lib.ObjectId;
+
+import java.util.Objects;
+
+class ExactCommitPredicate extends IndexPredicate<ChangeData> {
+  private final ObjectId id;
+
+  ExactCommitPredicate(ObjectId id) {
+    super(ChangeField.COMMIT, id.name());
+    this.id = id;
+  }
+
+  @Override
+  public boolean match(final ChangeData object) throws OrmException {
+    String idStr = id.name();
+    for (PatchSet p : object.patchSets()) {
+      if (p.getRevision() != null && p.getRevision().get() != null) {
+        if (Objects.equals(p.getRevision().get(), idStr)) {
+          return true;
+        }
+      }
+    }
+    return false;
+  }
+
+  @Override
+  public int getCost() {
+    return 1;
+  }
+}

gerrit-server/src/main/java/com/google/gerrit/server/query/change/InternalChangeQuery.java

@@ -35,7 +35,6 @@ import com.google.gerrit.server.query.QueryParseException;
 import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
 
-import org.eclipse.jgit.lib.AbbreviatedObjectId;
 import org.eclipse.jgit.lib.ObjectId;
 
 import java.util.ArrayList;
@@ -67,8 +66,8 @@ public class InternalChangeQuery {
     return new ChangeStatusPredicate(status);
   }
 
-  private static Predicate<ChangeData> commit(AbbreviatedObjectId id) {
+  private static Predicate<ChangeData> commit(ObjectId id) {
-    return new CommitPredicate(id);
+    return new ExactCommitPredicate(id);
   }
 
   private final QueryProcessor qp;
@@ -130,7 +129,7 @@ public class InternalChangeQuery {
       List<String> hashes, int batchSize) throws OrmException {
     List<Predicate<ChangeData>> commits = new ArrayList<>(hashes.size());
     for (String s : hashes) {
-      commits.add(commit(AbbreviatedObjectId.fromString(s)));
+      commits.add(commit(ObjectId.fromString(s)));
     }
     int numBatches = (hashes.size() / batchSize) + 1;
     List<Predicate<ChangeData>> queries = new ArrayList<>(numBatches);
@@ -164,12 +163,8 @@ public class InternalChangeQuery {
     return query(and(new ExactTopicPredicate(schema(indexes), topic), open()));
   }
 
-  public List<ChangeData> byCommitPrefix(String prefix) throws OrmException {
-    return query(commit(AbbreviatedObjectId.fromString(prefix)));
-  }
-
   public List<ChangeData> byCommit(ObjectId id) throws OrmException {
-    return query(commit(AbbreviatedObjectId.fromObjectId(id)));
+    return query(commit(id));
   }
 
   public List<ChangeData> byProjectGroups(Project.NameKey project,