Enable parallel evaluation of 'e' in query expressions of the form 'buildfiles(e)'.

--
MOS_MIGRATED_REVID=139787078

1 files changed, 2 insertions, 1 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/query2/engine/BuildFilesFunction.java b/src/main/java/com/google/devtools/build/lib/query2/engine/BuildFilesFunction.java
index 81f20d4a74..0e65cbdf05 100644
--- a/src/main/java/com/google/devtools/build/lib/query2/engine/BuildFilesFunction.java
+++ b/src/main/java/com/google/devtools/build/lib/query2/engine/BuildFilesFunction.java
@@ -52,7 +52,7 @@ class BuildFilesFunction implements QueryFunction {
     env.eval(
         args.get(0).getExpression(),
         context,
-        new Callback<T>() {
+        new ThreadSafeCallback<T>() {
           @Override
           public void process(Iterable<T> partialResult)
               throws QueryException, InterruptedException {
@@ -73,6 +73,7 @@ class BuildFilesFunction implements QueryFunction {
       List<Argument> args,
       ThreadSafeCallback<T> callback,
       ForkJoinPool forkJoinPool) throws QueryException, InterruptedException {
+    // 'eval' is written in such a way that it enables parallel evaluation of 'expression'.
     eval(env, context, expression, args, callback);
   }