Introduce RefDatabase#hasFastTipsWithSha1

The reftable format supports fast inverse (SHA1 => ref) queries.

If the ref database does not support fast inverse queries, it may be
advantageous to build a complete SHA1 to ref map in advance for
multiple uses. To let applications decide, this function indicates
whether the inverse map is available.

Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Change-Id: Idaf7e01075906972ec21332cade285289619c2b3

2 files changed, 70 insertions, 0 deletions

diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/FileReftableTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/FileReftableTest.java
index 0e06d459a2..cdc64fa1b2 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/FileReftableTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/FileReftableTest.java
@@ -155,6 +155,8 @@ public class FileReftableTest extends SampleDataRepositoryTestCase {
 		assertFalse(b.isSymbolic());
 		assertTrue(b.isPeeled());
 		assertEquals(bCommit, b.getObjectId().name());
+
+		assertTrue(db.getRefDatabase().hasFastTipsWithSha1());
 	}
 
 	@Test
@@ -169,6 +171,8 @@ public class FileReftableTest extends SampleDataRepositoryTestCase {
 		assertFalse(b.isSymbolic());
 		assertTrue(b.isPeeled());
 		assertEquals(bCommit, b.getObjectId().name());
+
+		assertFalse(db.getRefDatabase().hasFastTipsWithSha1());
 	}
 
 	@Test
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/reftable/ReftableTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/reftable/ReftableTest.java
index 45e6c7d128..daf540c413 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/reftable/ReftableTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/reftable/ReftableTest.java
@@ -177,6 +177,67 @@ public class ReftableTest {
 	}
 
 	@Test
+	public void hasObjMapRefs() throws IOException {
+		ArrayList<Ref> refs = new ArrayList<>();
+		refs.add(ref(MASTER, 1));
+		byte[] table = write(refs);
+		ReftableReader t = read(table);
+		assertTrue(t.hasObjectMap());
+	}
+
+	@Test
+	public void hasObjMapRefsSmallTable() throws IOException {
+		ArrayList<Ref> refs = new ArrayList<>();
+		ReftableConfig cfg = new ReftableConfig();
+		cfg.setIndexObjects(false);
+		refs.add(ref(MASTER, 1));
+		byte[] table = write(refs);
+		ReftableReader t = read(table);
+		assertTrue(t.hasObjectMap());
+	}
+
+	@Test
+	public void hasObjLogs() throws IOException {
+		PersonIdent who = new PersonIdent("Log", "Ger", 1500079709, -8 * 60);
+		String msg = "test";
+		ReftableConfig cfg = new ReftableConfig();
+		cfg.setIndexObjects(false);
+
+		ByteArrayOutputStream buffer = new ByteArrayOutputStream();
+		ReftableWriter writer = new ReftableWriter(buffer)
+			.setMinUpdateIndex(1)
+			.setConfig(cfg)
+			.setMaxUpdateIndex(1)
+			.begin();
+
+		writer.writeLog("master", 1, who, ObjectId.zeroId(), id(1), msg);
+		writer.finish();
+		byte[] table = buffer.toByteArray();
+
+		ReftableReader t = read(table);
+		assertTrue(t.hasObjectMap());
+	}
+
+	@Test
+	public void hasObjMapRefsNoIndexObjects() throws IOException {
+		ArrayList<Ref> refs = new ArrayList<>();
+		ReftableConfig cfg = new ReftableConfig();
+		cfg.setIndexObjects(false);
+		cfg.setRefBlockSize(256);
+		cfg.setAlignBlocks(true);
+
+		// Fill up 5 blocks.
+		int N = 256 * 5 / 25;
+		for (int i= 0; i < N; i++) {
+			refs.add(ref(String.format("%02d/xxxxxxxxxx", i), i));
+		}
+		byte[] table = write(refs, cfg);
+
+		ReftableReader t = read(table);
+		assertFalse(t.hasObjectMap());
+	}
+
+	@Test
 	public void oneIdRef() throws IOException {
 		Ref exp = ref(MASTER, 1);
 		byte[] table = write(exp);
@@ -936,8 +997,13 @@ public class ReftableTest {
 	}
 
 	private byte[] write(Collection<Ref> refs) throws IOException {
+		return write(refs, new ReftableConfig());
+	}
+
+	private byte[] write(Collection<Ref> refs, ReftableConfig cfg) throws IOException {
 		ByteArrayOutputStream buffer = new ByteArrayOutputStream();
 		stats = new ReftableWriter(buffer)
+				.setConfig(cfg)
 				.begin()
 				.sortAndWriteRefs(refs)
 				.finish()