Add a comment clarifying the soundness of not doing edge filtering during the DTC construction of the universe argument to 'rdeps'.

RELNOTES: None
PiperOrigin-RevId: 207884395

1 files changed, 6 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/query2/SkyQueryEnvironment.java b/src/main/java/com/google/devtools/build/lib/query2/SkyQueryEnvironment.java
index 0c759a8444..8918af1ea1 100644
--- a/src/main/java/com/google/devtools/build/lib/query2/SkyQueryEnvironment.java
+++ b/src/main/java/com/google/devtools/build/lib/query2/SkyQueryEnvironment.java
@@ -1208,6 +1208,9 @@ public class SkyQueryEnvironment extends AbstractBlazeQueryEnvironment<Target>
       QueryExpressionContext<Target> context,
       Callback<Target> callback) {
     return transformAsync(
+        // Even if we need to do edge filtering, it's fine to construct the rdeps universe via an
+        // unfiltered DTC visitation; the subsequent rdeps visitation will perform the edge
+        // filtering.
         getUnfilteredUniverseDTCSkyKeyPredicateFuture(universe, context),
         unfilteredUniversePredicate -> ParallelSkyQueryUtils.getRdepsInUniverseUnboundedParallel(
             this, expression, unfilteredUniversePredicate, context, callback, packageSemaphore));
@@ -1236,6 +1239,9 @@ public class SkyQueryEnvironment extends AbstractBlazeQueryEnvironment<Target>
       QueryExpressionContext<Target> context,
       Callback<Target> callback) {
     return transformAsync(
+        // Even if we need to do edge filtering, it's fine to construct the rdeps universe via an
+        // unfiltered DTC visitation; the subsequent rdeps visitation will perform the edge
+        // filtering.
         getUnfilteredUniverseDTCSkyKeyPredicateFuture(universe, context),
         universePredicate -> ParallelSkyQueryUtils.getRdepsInUniverseBoundedParallel(
             this, expression, depth, universePredicate, context, callback, packageSemaphore));