diff --git a/db/compaction/compaction_iterator.cc b/db/compaction/compaction_iterator.cc
index 85d1c039bd3..81e38be352b 100644
--- a/db/compaction/compaction_iterator.cc
+++ b/db/compaction/compaction_iterator.cc
@@ -229,17 +229,20 @@ bool CompactionIterator::InvokeFilterIfNeeded(bool* need_skip,
   }
 
   if (ikey_.type != kTypeValue && ikey_.type != kTypeBlobIndex &&
-      ikey_.type != kTypeWideColumnEntity) {
+      ikey_.type != kTypeWideColumnEntity && ikey_.type != kTypeDeletion) {
     return true;
   }
 
   CompactionFilter::Decision decision =
       CompactionFilter::Decision::kUndetermined;
-  CompactionFilter::ValueType value_type =
-      ikey_.type == kTypeValue ? CompactionFilter::ValueType::kValue
-      : ikey_.type == kTypeBlobIndex
-          ? CompactionFilter::ValueType::kBlobIndex
-          : CompactionFilter::ValueType::kWideColumnEntity;
+  CompactionFilter::ValueType value_type = CompactionFilter::ValueType::kValue;
+  if (ikey_.type == kTypeBlobIndex) {
+    value_type = CompactionFilter::ValueType::kBlobIndex;
+  } else if (ikey_.type == kTypeWideColumnEntity) {
+    value_type = CompactionFilter::ValueType::kWideColumnEntity;
+  } else if (ikey_.type == kTypeDeletion) {
+    value_type = CompactionFilter::ValueType::kDeletion;
+  }
 
   // Hack: pass internal key to BlobIndexCompactionFilter since it needs
   // to get sequence number.
diff --git a/db/compaction/compaction_iterator_test.cc b/db/compaction/compaction_iterator_test.cc
index 699e629693d..7b4e8985024 100644
--- a/db/compaction/compaction_iterator_test.cc
+++ b/db/compaction/compaction_iterator_test.cc
@@ -719,6 +719,40 @@ TEST_P(CompactionIteratorTest, SingleMergeOperand) {
   ASSERT_EQ("cv1cv2", c_iter_->value().ToString());
 }
 
+TEST_P(CompactionIteratorTest, RemoveAllSingleDeletes) {
+  struct Filter : public CompactionFilter {
+    Decision UnsafeFilter(int /*level*/, const Slice& key, ValueType t,
+                          const Slice& /*existing_value*/,
+                          std::string* /*new_value*/,
+                          std::string* skip_until) const override {
+      if (t == ValueType::kDeletion) {
+        *skip_until = key.ToString();
+        skip_until->back() += 1;
+        filtered += 1;
+        return Decision::kRemoveAndSkipUntil;
+      }
+      return Decision::kKeep;
+    }
+
+    const char* Name() const override {
+      return "CompactionIteratorTest.SingleDelete::Filter";
+    }
+    mutable size_t filtered = 0;
+  };
+
+  Filter filter;
+  InitIterators(
+      {test::KeyStr("a", 70, kTypeDeletion), test::KeyStr("a", 50, kTypeValue),
+       test::KeyStr("c", 70, kTypeDeletion),
+       test::KeyStr("c", 50, kTypeDeletion)},
+      {"", "a", "", ""}, {}, {}, kMaxSequenceNumber, kMaxSequenceNumber,
+      nullptr, &filter);
+
+  c_iter_->SeekToFirst();
+  ASSERT_TRUE(!c_iter_->Valid());
+  ASSERT_EQ(filter.filtered, 2);
+}
+
 // In bottommost level, values earlier than earliest snapshot can be output
 // with sequence = 0.
 TEST_P(CompactionIteratorTest, ZeroOutSequenceAtBottomLevel) {
diff --git a/file/writable_file_writer.cc b/file/writable_file_writer.cc
index 908878a5fae..72a66b1bb2c 100644
--- a/file/writable_file_writer.cc
+++ b/file/writable_file_writer.cc
@@ -69,6 +69,10 @@ IOStatus WritableFileWriter::Append(const Slice& data, uint32_t crc32c_checksum,
                                  io_options, nullptr);
   }
 
+  // The buffer initialization code previously in ctor.
+  if (buf_.Capacity() == 0) {
+    buf_.AllocateNewBuffer(std::min((size_t)65536, max_buffer_size_));
+  }
   // See whether we need to enlarge the buffer to avoid the flush
   if (buf_.Capacity() - buf_.CurrentSize() < left) {
     for (size_t cap = buf_.Capacity();
diff --git a/file/writable_file_writer.h b/file/writable_file_writer.h
index aac0f59491e..30c278cfb9a 100644
--- a/file/writable_file_writer.h
+++ b/file/writable_file_writer.h
@@ -202,7 +202,8 @@ class WritableFileWriter {
     TEST_SYNC_POINT_CALLBACK("WritableFileWriter::WritableFileWriter:0",
                              reinterpret_cast<void*>(max_buffer_size_));
     buf_.Alignment(writable_file_->GetRequiredBufferAlignment());
-    buf_.AllocateNewBuffer(std::min((size_t)65536, max_buffer_size_));
+    // Moved to `Append` to reduce memory usage of unused writer.
+    // buf_.AllocateNewBuffer(std::min((size_t)65536, max_buffer_size_));
     std::for_each(listeners.begin(), listeners.end(),
                   [this](const std::shared_ptr<EventListener>& e) {
                     if (e->ShouldBeNotifiedOnFileIO()) {
diff --git a/include/rocksdb/compaction_filter.h b/include/rocksdb/compaction_filter.h
index 410ee4d3ab0..9592b8e4a7b 100644
--- a/include/rocksdb/compaction_filter.h
+++ b/include/rocksdb/compaction_filter.h
@@ -67,6 +67,7 @@ class CompactionFilter : public Customizable {
     kBlobIndex,
     // Wide-column entity
     kWideColumnEntity,
+    kDeletion,  // used only by TiKV's region range filter.
   };
 
   // Potential decisions that can be returned by the compaction filter's
@@ -254,9 +255,13 @@ class CompactionFilter : public Customizable {
       case ValueType::kBlobIndex:
         return Decision::kKeep;
 
-      default:
+      case ValueType::kDeletion:
+        // Should not appear in this API.
         assert(false);
         return Decision::kKeep;
+
+      default:
+        return Decision::kKeep;
     }
   }
 
@@ -298,8 +303,23 @@ class CompactionFilter : public Customizable {
       return Decision::kKeep;
     }
 
-    return FilterV2(level, key, value_type, *existing_value, new_value,
-                    skip_until);
+    return UnsafeFilter(level, key, value_type, *existing_value, new_value,
+                        skip_until);
+  }
+
+  // This interface is reserved for TiKV's region range filter. Only this
+  // interface can accept `value_type=kTypeDeletion`.
+  virtual Decision UnsafeFilter(int level, const Slice& key,
+                                ValueType value_type,
+                                const Slice& existing_value,
+                                std::string* new_value,
+                                std::string* skip_until) const {
+    if (value_type != ValueType::kDeletion) {
+      return FilterV2(level, key, value_type, existing_value, new_value,
+                      skip_until);
+    } else {
+      return Decision::kKeep;
+    }
   }
 
   // Internal (BlobDB) use only. Do not override in application code.