diff --git a/dbms/src/DataStreams/MergingSortedBlockInputStream.cpp b/dbms/src/DataStreams/MergingSortedBlockInputStream.cpp
index 19d3453d3c3..7275cb11726 100644
--- a/dbms/src/DataStreams/MergingSortedBlockInputStream.cpp
+++ b/dbms/src/DataStreams/MergingSortedBlockInputStream.cpp
@@ -146,6 +146,9 @@ bool MergingSortedBlockInputStream::MergeStopCondition::checkStop() const
     if (!count_average)
         return total_rows == max_block_size;
 
+    if (total_rows == 0)
+        return false;
+
     size_t average = sum / total_rows;
     return total_rows >= average;
 }
@@ -155,6 +158,9 @@ bool MergingSortedBlockInputStream::MergeStopCondition::checkStop(size_t total_r
     if (!count_average)
         return total_rows == max_block_size;
 
+    if (total_rows == 0)
+        return false;
+
     size_t sum = 0;
     for (const auto & [granularity, rows_count] : blocks_granularity)
         sum += granularity * rows_count;
diff --git a/dbms/src/Storages/MergeTree/MergeList.cpp b/dbms/src/Storages/MergeTree/MergeList.cpp
index 5f590de9bde..179f0354999 100644
--- a/dbms/src/Storages/MergeTree/MergeList.cpp
+++ b/dbms/src/Storages/MergeTree/MergeList.cpp
@@ -29,6 +29,7 @@ MergeListElement::MergeListElement(const std::string & database, const std::stri
 
         total_size_bytes_compressed += source_part->bytes_on_disk;
         total_size_marks += source_part->getMarksCount();
+        total_rows_count += source_part->index_granularity.getTotalRows();
     }
 
     if (!future_part.parts.empty())
@@ -60,6 +61,7 @@ MergeInfo MergeListElement::getInfo() const
     res.num_parts = num_parts;
     res.total_size_bytes_compressed = total_size_bytes_compressed;
     res.total_size_marks = total_size_marks;
+    res.total_rows_count = total_rows_count;
     res.bytes_read_uncompressed = bytes_read_uncompressed.load(std::memory_order_relaxed);
     res.bytes_written_uncompressed = bytes_written_uncompressed.load(std::memory_order_relaxed);
     res.rows_read = rows_read.load(std::memory_order_relaxed);
diff --git a/dbms/src/Storages/MergeTree/MergeList.h b/dbms/src/Storages/MergeTree/MergeList.h
index 2d800c85896..dc2d1c80682 100644
--- a/dbms/src/Storages/MergeTree/MergeList.h
+++ b/dbms/src/Storages/MergeTree/MergeList.h
@@ -36,6 +36,7 @@ struct MergeInfo
     UInt64 num_parts;
     UInt64 total_size_bytes_compressed;
     UInt64 total_size_marks;
+    UInt64 total_rows_count;
     UInt64 bytes_read_uncompressed;
     UInt64 bytes_written_uncompressed;
     UInt64 rows_read;
@@ -67,6 +68,7 @@ struct MergeListElement : boost::noncopyable
 
     UInt64 total_size_bytes_compressed{};
     UInt64 total_size_marks{};
+    UInt64 total_rows_count{};
     std::atomic<UInt64> bytes_read_uncompressed{};
     std::atomic<UInt64> bytes_written_uncompressed{};
 
diff --git a/dbms/src/Storages/MergeTree/MergeTreeDataMergerMutator.cpp b/dbms/src/Storages/MergeTree/MergeTreeDataMergerMutator.cpp
index ac3c8d6fb0f..9b5ae02274e 100644
--- a/dbms/src/Storages/MergeTree/MergeTreeDataMergerMutator.cpp
+++ b/dbms/src/Storages/MergeTree/MergeTreeDataMergerMutator.cpp
@@ -536,8 +536,7 @@ MergeTreeData::MutableDataPartPtr MergeTreeDataMergerMutator::mergePartsToTempor
     new_data_part->relative_path = TMP_PREFIX + future_part.name;
     new_data_part->is_temp = true;
 
-    /// TODO(alesap) fixme to sum of all index_granularity
-    size_t sum_input_rows_upper_bound = merge_entry->total_size_marks * data.index_granularity_info.fixed_index_granularity;
+    size_t sum_input_rows_upper_bound = merge_entry->total_rows_count;
 
     MergeAlgorithm merge_alg = chooseMergeAlgorithm(parts, sum_input_rows_upper_bound, gathering_columns, deduplicate);