optimize file ingestion checks for range deletion overlap

db/external_sst_file_basic_test.cc

@@ -605,8 +605,9 @@ TEST_F(ExternalSSTFileBasicTest, IngestionWithRangeDeletions) {
   ASSERT_EQ(1, NumTableFilesAtLevel(kNumLevels - 2));
   ASSERT_EQ(1, NumTableFilesAtLevel(options.num_levels - 1));
 
-  // overlaps with memtable, so flush is triggered (thus file count increases by
-  // two at this step).
+  // ingested file overlaps with memtable, so flush is triggered before the file
+  // is ingested such that the ingested data is considered newest. So L0 file
+  // count increases by two.
   ASSERT_OK(GenerateAndAddExternalFile(
       options, {100, 140}, {ValueType::kTypeValue, ValueType::kTypeValue},
       file_id++, &true_data));

db/external_sst_file_ingestion_job.cc

@@ -622,10 +622,11 @@ Status ExternalSstFileIngestionJob::IngestedFileOverlapWithLevel(
   // Files are opened lazily when the iterator needs them, thus range deletions
   // are also added lazily to the aggregator. We need to check for range
   // deletion overlap only in the case where there's no point-key overlap. Then,
-  // we've already opened the file containing the first key after the range, and
-  // iterated backward to the last key before the range. So any files maybe
-  // containing range deletions overlapping the ingested file must have been
-  // opened and had their range deletions added to the aggregator.
+  // we've already opened the file with range containing the ingested file's
+  // begin key, and iterated through all files until the one containing the
+  // ingested file's end key. So any files maybe containing range deletions
+  // overlapping the ingested file must have been opened and had their range
+  // deletions added to the aggregator.
   RangeDelAggregator range_del_agg(cfd_->internal_comparator(),
                                    {} /* snapshots */,
                                    false /* collapse_deletions */);

db/range_del_aggregator.cc

@@ -155,7 +155,7 @@ bool RangeDelAggregator::IsRangeOverlapped(const Slice& start,
       if (icmp_.user_comparator()->Compare(start, tombstone.end_key_) < 0 &&
           icmp_.user_comparator()->Compare(tombstone.start_key_, end) <= 0 &&
           icmp_.user_comparator()->Compare(tombstone.start_key_,
-                                           tombstone.end_key_) != 0) {
+                                           tombstone.end_key_) < 0) {
         return true;
       }
     }