1 files changed, 7 insertions, 0 deletions
diff --git a/src/main/java/com/google/devtools/build/skyframe/WalkableGraph.java b/src/main/java/com/google/devtools/build/skyframe/WalkableGraph.java
index a55bbc5415..b5b744f6af 100644
--- a/src/main/java/com/google/devtools/build/skyframe/WalkableGraph.java
+++ b/src/main/java/com/google/devtools/build/skyframe/WalkableGraph.java
@@ -103,6 +103,13 @@ public interface WalkableGraph {
         Set<SkyKey> roots, int numThreads, ExtendedEventHandler eventHandler)
         throws InterruptedException;
 
+    /**
+     * Returns true if this instance has already been used to {@link #prepareAndGet} {@code roots}.
+     * If so, cached results from {@link #prepareAndGet} can be re-used safely, potentially saving
+     * some processing time.
+     */
+    boolean isUpToDate(Set<SkyKey> roots);
+
     /** Returns the {@link SkyKey} that defines this universe. */
     SkyKey getUniverseKey(Collection<String> roots, String offset);
   }