Update DfsGarbageCollector to not read back a pack index.

Previously, the Dfs GC excluded objects from packs by passing a
previously written index to the PackWriter. Reading back a file on
Dfs is slow. Instead, allow the PackWriter to expose the objects
included in a pack and forward that to invocations of excludeObjects() .

Change-Id: I377cb4ab07f62cf790505e1eeb0b2efe81897c79

3 files changed, 73 insertions, 28 deletions

diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/storage/dfs/DfsGarbageCollector.java b/org.eclipse.jgit/src/org/eclipse/jgit/storage/dfs/DfsGarbageCollector.java
index 4397813036..21f01ad6b4 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/storage/dfs/DfsGarbageCollector.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/storage/dfs/DfsGarbageCollector.java
@@ -82,7 +82,7 @@ public class DfsGarbageCollector {
 
 	private final List<PackWriter.Statistics> newPackStats;
 
-	private final List<DfsPackFile> newPackList;
+	private final List<PackWriter.ObjectIdSet> newPackObj;
 
 	private DfsReader ctx;
 
@@ -116,7 +116,7 @@ public class DfsGarbageCollector {
 		objdb = repo.getObjectDatabase();
 		newPackDesc = new ArrayList<DfsPackDescription>(4);
 		newPackStats = new ArrayList<PackWriter.Statistics>(4);
-		newPackList = new ArrayList<DfsPackFile>(4);
+		newPackObj = new ArrayList<PackWriter.ObjectIdSet>(4);
 
 		packConfig = new PackConfig(repo);
 		packConfig.setIndexVersion(2);
@@ -244,8 +244,8 @@ public class DfsGarbageCollector {
 
 		PackWriter pw = newPackWriter();
 		try {
-			for (DfsPackFile pack : newPackList)
-				pw.excludeObjects(pack.getPackIndex(ctx));
+			for (PackWriter.ObjectIdSet packedObjs : newPackObj)
+				pw.excludeObjects(packedObjs);
 			pw.preparePack(pm, nonHeads, allHeads);
 			if (0 < pw.getObjectCount())
 				writePack(GC, pw, pm);
@@ -259,10 +259,6 @@ public class DfsGarbageCollector {
 			return;
 
 		// TODO(sop) This is ugly. The garbage pack needs to be deleted.
-		List<PackIndex> newIdx = new ArrayList<PackIndex>(newPackList.size());
-		for (DfsPackFile pack : newPackList)
-			newIdx.add(pack.getPackIndex(ctx));
-
 		PackWriter pw = newPackWriter();
 		try {
 			RevWalk pool = new RevWalk(ctx);
@@ -272,7 +268,7 @@ public class DfsGarbageCollector {
 				for (PackIndex.MutableEntry ent : oldIdx) {
 					pm.update(1);
 					ObjectId id = ent.toObjectId();
-					if (pool.lookupOrNull(id) != null || anyIndexHas(newIdx, id))
+					if (pool.lookupOrNull(id) != null || anyPackHas(id))
 						continue;
 
 					int type = oldPack.getObjectType(ctx, ent.getOffset());
@@ -287,9 +283,9 @@ public class DfsGarbageCollector {
 		}
 	}
 
-	private static boolean anyIndexHas(List<PackIndex> list, AnyObjectId id) {
-		for (PackIndex idx : list)
-			if (idx.hasObject(id))
+	private boolean anyPackHas(AnyObjectId id) {
+		for (PackWriter.ObjectIdSet packedObjs : newPackObj)
+			if (packedObjs.contains(id))
 				return true;
 		return false;
 	}
@@ -336,6 +332,13 @@ public class DfsGarbageCollector {
 			out.close();
 		}
 
+		final List<ObjectId> packedObjs = pw.getObjectList();
+		newPackObj.add(new PackWriter.ObjectIdSet() {
+			public boolean contains(AnyObjectId objectId) {
+				return 0 <= Collections.binarySearch(packedObjs, objectId);
+			}
+		});
+
 		PackWriter.Statistics stats = pw.getStatistics();
 		pack.setPackStats(stats);
 		pack.setFileSize(PACK, stats.getTotalBytes());
@@ -343,7 +346,8 @@ public class DfsGarbageCollector {
 		pack.setDeltaCount(stats.getTotalDeltas());
 		objectsPacked += stats.getTotalObjects();
 		newPackStats.add(stats);
-		newPackList.add(DfsBlockCache.getInstance().getOrCreate(pack, null));
+
+		DfsBlockCache.getInstance().getOrCreate(pack, null);
 		return pack;
 	}
 }
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/storage/file/GC.java b/org.eclipse.jgit/src/org/eclipse/jgit/storage/file/GC.java
index cf4ec58936..45f382316a 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/storage/file/GC.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/storage/file/GC.java
@@ -70,6 +70,7 @@ import org.eclipse.jgit.errors.IncorrectObjectTypeException;
 import org.eclipse.jgit.errors.MissingObjectException;
 import org.eclipse.jgit.errors.NoWorkTreeException;
 import org.eclipse.jgit.internal.JGitText;
+import org.eclipse.jgit.lib.AnyObjectId;
 import org.eclipse.jgit.lib.ConfigConstants;
 import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.FileMode;
@@ -83,6 +84,7 @@ import org.eclipse.jgit.revwalk.ObjectWalk;
 import org.eclipse.jgit.revwalk.RevObject;
 import org.eclipse.jgit.revwalk.RevWalk;
 import org.eclipse.jgit.storage.pack.PackWriter;
+import org.eclipse.jgit.storage.pack.PackWriter.ObjectIdSet;
 import org.eclipse.jgit.treewalk.TreeWalk;
 import org.eclipse.jgit.treewalk.filter.TreeFilter;
 import org.eclipse.jgit.util.FileUtils;
@@ -498,10 +500,10 @@ public class GC {
 				tagTargets.add(ref.getPeeledObjectId());
 		}
 
-		List<PackIndex> excluded = new LinkedList<PackIndex>();
-		for (PackFile f : repo.getObjectDatabase().getPacks())
+		List<ObjectIdSet> excluded = new LinkedList<ObjectIdSet>();
+		for (final PackFile f : repo.getObjectDatabase().getPacks())
 			if (f.shouldBeKept())
-				excluded.add(f.getIndex());
+				excluded.add(objectIdSet(f.getIndex()));
 
 		tagTargets.addAll(allHeads);
 		nonHeads.addAll(indexObjects);
@@ -513,7 +515,7 @@ public class GC {
 					tagTargets, excluded);
 			if (heads != null) {
 				ret.add(heads);
-				excluded.add(0, heads.getIndex());
+				excluded.add(0, objectIdSet(heads.getIndex()));
 			}
 		}
 		if (!nonHeads.isEmpty()) {
@@ -632,7 +634,7 @@ public class GC {
 
 	private PackFile writePack(Set<? extends ObjectId> want,
 			Set<? extends ObjectId> have, Set<ObjectId> tagTargets,
-			List<PackIndex> excludeObjects) throws IOException {
+			List<ObjectIdSet> excludeObjects) throws IOException {
 		File tmpPack = null;
 		File tmpIdx = null;
 		PackWriter pw = new PackWriter(repo);
@@ -643,7 +645,7 @@ public class GC {
 			if (tagTargets != null)
 				pw.setTagTargets(tagTargets);
 			if (excludeObjects != null)
-				for (PackIndex idx : excludeObjects)
+				for (ObjectIdSet idx : excludeObjects)
 					pw.excludeObjects(idx);
 			pw.preparePack(pm, want, have);
 			if (pw.getObjectCount() == 0)
@@ -855,4 +857,11 @@ public class GC {
 		expireAgeMillis = -1;
 	}
 
+	private static ObjectIdSet objectIdSet(final PackIndex idx) {
+		return new ObjectIdSet() {
+			public boolean contains(AnyObjectId objectId) {
+				return idx.hasObject(objectId);
+			}
+		};
+	}
 }
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/storage/pack/PackWriter.java b/org.eclipse.jgit/src/org/eclipse/jgit/storage/pack/PackWriter.java
index bfb6c652d9..b199d4feef 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/storage/pack/PackWriter.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/storage/pack/PackWriter.java
@@ -103,7 +103,6 @@ import org.eclipse.jgit.revwalk.RevObject;
 import org.eclipse.jgit.revwalk.RevSort;
 import org.eclipse.jgit.revwalk.RevTag;
 import org.eclipse.jgit.revwalk.RevTree;
-import org.eclipse.jgit.storage.file.PackIndex;
 import org.eclipse.jgit.storage.file.PackIndexWriter;
 import org.eclipse.jgit.util.BlockList;
 import org.eclipse.jgit.util.TemporaryBuffer;
@@ -144,6 +143,18 @@ import org.eclipse.jgit.util.TemporaryBuffer;
 public class PackWriter {
 	private static final int PACK_VERSION_GENERATED = 2;
 
+	/** A collection of object ids. */
+	public interface ObjectIdSet {
+		/**
+		 * Returns true if the objectId is contained within the collection.
+		 *
+		 * @param objectId
+		 *            the objectId to find
+		 * @return whether the collection contains the objectId.
+		 */
+		boolean contains(AnyObjectId objectId);
+	}
+
 	private static final Map<WeakReference<PackWriter>, Boolean> instances =
 			new ConcurrentHashMap<WeakReference<PackWriter>, Boolean>();
 
@@ -206,9 +217,9 @@ public class PackWriter {
 
 	private Set<ObjectId> tagTargets = Collections.emptySet();
 
-	private PackIndex[] excludeInPacks;
+	private ObjectIdSet[] excludeInPacks;
 
-	private PackIndex excludeInPackLast;
+	private ObjectIdSet excludeInPackLast;
 
 	private Deflater myDeflater;
 
@@ -508,18 +519,39 @@ public class PackWriter {
 	}
 
 	/**
+	 * Returns the object ids in the pack file that was created by this writer,
+	 * sorted by name.
+	 *
+	 * This method can only be invoked after
+	 * {@link #writePack(ProgressMonitor, ProgressMonitor, OutputStream)} has
+	 * been invoked and completed successfully.
+	 *
+	 * @return number of objects in pack.
+	 * @throws IOException
+	 *             a cached pack cannot supply its object ids.
+	 */
+	public List<ObjectId> getObjectList() throws IOException {
+		if (!cachedPacks.isEmpty())
+			throw new IOException(
+					JGitText.get().cachedPacksPreventsListingObjects);
+
+		return Collections.unmodifiableList(
+				(List<? extends ObjectId>) sortByName());
+	}
+
+	/**
 	 * Add a pack index whose contents should be excluded from the result.
 	 *
 	 * @param idx
 	 *            objects in this index will not be in the output pack.
 	 */
-	public void excludeObjects(PackIndex idx) {
+	public void excludeObjects(ObjectIdSet idx) {
 		if (excludeInPacks == null) {
-			excludeInPacks = new PackIndex[] { idx };
+			excludeInPacks = new ObjectIdSet[] { idx };
 			excludeInPackLast = idx;
 		} else {
 			int cnt = excludeInPacks.length;
-			PackIndex[] newList = new PackIndex[cnt + 1];
+			ObjectIdSet[] newList = new ObjectIdSet[cnt + 1];
 			System.arraycopy(excludeInPacks, 0, newList, 0, cnt);
 			newList[cnt] = idx;
 			excludeInPacks = newList;
@@ -1798,10 +1830,10 @@ public class PackWriter {
 	private boolean exclude(AnyObjectId objectId) {
 		if (excludeInPacks == null)
 			return false;
-		if (excludeInPackLast.hasObject(objectId))
+		if (excludeInPackLast.contains(objectId))
 			return true;
-		for (PackIndex idx : excludeInPacks) {
-			if (idx.hasObject(objectId)) {
+		for (ObjectIdSet idx : excludeInPacks) {
+			if (idx.contains(objectId)) {
 				excludeInPackLast = idx;
 				return true;
 			}