diff --git a/storage/innobase/ddl/ddl0builder.cc b/storage/innobase/ddl/ddl0builder.cc
index 5e61568d89f..27f0f88ab9b 100644
--- a/storage/innobase/ddl/ddl0builder.cc
+++ b/storage/innobase/ddl/ddl0builder.cc
@@ -389,6 +389,22 @@ void Merge_cursor::clear_eof() noexcept {
   }
 }
 
+void Merge_cursor::reset_for_next_range() noexcept {
+  while (!m_pq.empty()) {
+    m_pq.pop();
+  }
+  m_err = DB_END_OF_INDEX;
+  for (auto cursor : m_cursors) {
+    cursor->m_err = DB_END_OF_INDEX;
+  }
+}
+
+void Merge_cursor::stage_inc() noexcept {
+  if (m_stage != nullptr) {
+    m_stage->inc(1);
+  }
+}
+
 dberr_t Merge_cursor::open() noexcept {
   ut_a(m_pq.empty());
   ut_a(!m_cursors.empty());
diff --git a/storage/innobase/ddl/ddl0merge.cc b/storage/innobase/ddl/ddl0merge.cc
index 26cdf2fd264..185d5e624e6 100644
--- a/storage/innobase/ddl/ddl0merge.cc
+++ b/storage/innobase/ddl/ddl0merge.cc
@@ -50,6 +50,7 @@ std::ostream &operator<<(std::ostream &out,
 
 /** Cursor for merging blocks from the same file. */
 struct Merge_file_sort::Cursor : private ut::Non_copyable {
+  friend class Merge_file_sort;
   /** Constructor.
   @param[in,out] builder        Index builder instance.
   @param[in] file               File to iterate over.
@@ -403,27 +404,68 @@ Merge_file_sort::Range Merge_file_sort::next_range(
 dberr_t Merge_file_sort::merge_rows(Cursor &cursor,
                                     Output_file &output_file) noexcept {
   dberr_t err;
-  ulint *offsets{};
-  const mrec_t *mrec{};
 
-  while ((err = cursor.fetch(mrec, offsets)) == DB_SUCCESS) {
-    /* If we are simply appending from a single partion then enable duplicate
-    key checking for the write phase. */
-    auto dup = cursor.size() == 0 ? m_merge_ctx->m_dup : nullptr;
+  const auto &file_readers = cursor.m_cursor.file_readers();
+  ut_a(file_readers.size() == 2);
 
-    err = output_file.write(mrec, offsets, dup);
+  const auto file_reader0 = file_readers[0];
+  const auto file_reader1 = file_readers[1];
+  File_reader *file_reader = nullptr;
 
-    if (unlikely(err != DB_SUCCESS)) {
+  const auto dup = m_merge_ctx->m_dup;
+
+  /* Merge two partitions */
+  while (!file_reader0->eof() && !file_reader1->eof()) {
+    auto cmp = cmp_rec_rec_simple(
+        file_reader0->m_mrec, file_reader1->m_mrec,
+        &(file_reader0->m_offsets[0]), &(file_reader1->m_offsets[0]),
+        file_reader0->m_index, dup != nullptr ? dup->m_table : nullptr);
+
+    /* Check for duplicates. */
+    if (cmp == 0 && dup != nullptr) {
+      dup->report(file_reader0->m_mrec, &(file_reader0->m_offsets[0]));
+    }
+
+    /* PFS stage monitoring */
+    cursor.m_cursor.stage_inc();
+
+    file_reader = cmp <= 0 ? file_reader0 : file_reader1;
+
+    err = output_file.write(file_reader->m_mrec, &(file_reader->m_offsets[0]),
+                            nullptr);
+    if (err != DB_SUCCESS) {
+      return err;
+    }
+    err = file_reader->next();
+
+    if (err != DB_SUCCESS) {
       break;
     }
+  }
 
-    err = cursor.next();
+  file_reader = file_reader0->eof() ? file_reader1 : file_reader0;
 
-    if (unlikely(err != DB_SUCCESS)) {
+  /* Process the remaining rows */
+  while (!file_reader->eof()) {
+    /* PFS stage monitoring */
+    cursor.m_cursor.stage_inc();
+
+    /* Check for duplicates when we are appending from a single partition */
+    err = output_file.write(file_reader->m_mrec, &(file_reader->m_offsets[0]),
+                            dup);
+    if (err != DB_SUCCESS) {
+      return err;
+    }
+
+    err = file_reader->next();
+    if (err != DB_SUCCESS) {
       break;
     }
   }
 
+  /* Clear the Merge_cursor to pass the subsequent checks in clear_eof() */
+  cursor.m_cursor.reset_for_next_range();
+
   return err;
 }
 
diff --git a/storage/innobase/include/ddl0impl-builder.h b/storage/innobase/include/ddl0impl-builder.h
index 4240c837722..156daa7cca3 100644
--- a/storage/innobase/include/ddl0impl-builder.h
+++ b/storage/innobase/include/ddl0impl-builder.h
@@ -541,6 +541,12 @@ struct Merge_cursor : public Load_cursor {
     return m_cursors.size();
   }
 
+  /** Clear m_pq, called at the end of merge_rows_fast() */
+  void reset_for_next_range() noexcept;
+
+  /* PFS stage monitoring */
+  void stage_inc() noexcept;
+
  private:
   /** @return the current cursor at the head of the queue. */
   [[nodiscard]] File_cursor *pop() noexcept;
diff --git a/storage/innobase/include/ddl0impl-file-reader.h b/storage/innobase/include/ddl0impl-file-reader.h
index d8032933fe1..340986747c2 100644
--- a/storage/innobase/include/ddl0impl-file-reader.h
+++ b/storage/innobase/include/ddl0impl-file-reader.h
@@ -37,6 +37,7 @@ namespace ddl {
 
 // Forward declaration
 struct File_cursor;
+struct Merge_file_sort;
 
 /** Read rows from the temporary file. */
 struct File_reader : private ut::Non_copyable {
@@ -150,6 +151,7 @@ struct File_reader : private ut::Non_copyable {
   uint64_t m_n_rows_read{};
 
   friend File_cursor;
+  friend Merge_file_sort;
 };
 
 }  // namespace ddl