diff --git a/src/Interpreters/Aggregator.cpp b/src/Interpreters/Aggregator.cpp
index b0f8f26c8e9..90af4352b42 100644
--- a/src/Interpreters/Aggregator.cpp
+++ b/src/Interpreters/Aggregator.cpp
@@ -2316,7 +2316,7 @@ void Aggregator::destroyAllAggregateStates(AggregatedDataVariants & result)
 }
 
 
-void Aggregator::setCancellationHook(const CancellationHook cancellation_hook)
+void Aggregator::setCancellationHook(const CancellationHook & cancellation_hook)
 {
     isCancelled = cancellation_hook;
 }
diff --git a/src/Interpreters/Aggregator.h b/src/Interpreters/Aggregator.h
index 331d50672ab..2a1224b0b48 100644
--- a/src/Interpreters/Aggregator.h
+++ b/src/Interpreters/Aggregator.h
@@ -134,7 +134,7 @@ struct AggregationDataWithNullKeyTwoLevel : public Base
 {
     using Base::impls;
 
-    AggregationDataWithNullKeyTwoLevel() {}
+    AggregationDataWithNullKeyTwoLevel() = default;
 
     template <typename Other>
     explicit AggregationDataWithNullKeyTwoLevel(const Other & other) : Base(other)
@@ -184,7 +184,7 @@ struct AggregationMethodOneNumber
 
     Data data;
 
-    AggregationMethodOneNumber() {}
+    AggregationMethodOneNumber() = default;
 
     template <typename Other>
     AggregationMethodOneNumber(const Other & other) : data(other.data) {}
@@ -199,8 +199,8 @@ struct AggregationMethodOneNumber
     // Insert the key from the hash table into columns.
     static void insertKeyIntoColumns(const Key & key, MutableColumns & key_columns, const Sizes & /*key_sizes*/)
     {
-        auto key_holder = reinterpret_cast<const char *>(&key);
-        auto column = static_cast<ColumnVectorHelper *>(key_columns[0].get());
+        const auto * key_holder = reinterpret_cast<const char *>(&key);
+        auto * column = static_cast<ColumnVectorHelper *>(key_columns[0].get());
         column->insertRawData<sizeof(FieldType)>(key_holder);
     }
 };
@@ -216,7 +216,7 @@ struct AggregationMethodString
 
     Data data;
 
-    AggregationMethodString() {}
+    AggregationMethodString() = default;
 
     template <typename Other>
     AggregationMethodString(const Other & other) : data(other.data) {}
@@ -242,7 +242,7 @@ struct AggregationMethodStringNoCache
 
     Data data;
 
-    AggregationMethodStringNoCache() {}
+    AggregationMethodStringNoCache() = default;
 
     template <typename Other>
     AggregationMethodStringNoCache(const Other & other) : data(other.data) {}
@@ -268,7 +268,7 @@ struct AggregationMethodFixedString
 
     Data data;
 
-    AggregationMethodFixedString() {}
+    AggregationMethodFixedString() = default;
 
     template <typename Other>
     AggregationMethodFixedString(const Other & other) : data(other.data) {}
@@ -293,7 +293,7 @@ struct AggregationMethodFixedStringNoCache
 
     Data data;
 
-    AggregationMethodFixedStringNoCache() {}
+    AggregationMethodFixedStringNoCache() = default;
 
     template <typename Other>
     AggregationMethodFixedStringNoCache(const Other & other) : data(other.data) {}
@@ -334,7 +334,7 @@ struct AggregationMethodSingleLowCardinalityColumn : public SingleColumnMethod
     static void insertKeyIntoColumns(const Key & key,
         MutableColumns & key_columns_low_cardinality, const Sizes & /*key_sizes*/)
     {
-        auto col = assert_cast<ColumnLowCardinality *>(key_columns_low_cardinality[0].get());
+        auto * col = assert_cast<ColumnLowCardinality *>(key_columns_low_cardinality[0].get());
 
         if constexpr (std::is_same_v<Key, StringRef>)
         {
@@ -360,7 +360,7 @@ struct AggregationMethodKeysFixed
 
     Data data;
 
-    AggregationMethodKeysFixed() {}
+    AggregationMethodKeysFixed() = default;
 
     template <typename Other>
     AggregationMethodKeysFixed(const Other & other) : data(other.data) {}
@@ -438,7 +438,7 @@ struct AggregationMethodSerialized
 
     Data data;
 
-    AggregationMethodSerialized() {}
+    AggregationMethodSerialized() = default;
 
     template <typename Other>
     AggregationMethodSerialized(const Other & other) : data(other.data) {}
@@ -449,7 +449,7 @@ struct AggregationMethodSerialized
 
     static void insertKeyIntoColumns(const StringRef & key, MutableColumns & key_columns, const Sizes &)
     {
-        auto pos = key.data;
+        const auto * pos = key.data;
         for (auto & column : key_columns)
             pos = column->deserializeAndInsertFromArena(pos);
     }
@@ -783,9 +783,9 @@ struct AggregatedDataVariants : private boost::noncopyable
         M(low_cardinality_keys128_two_level) \
         M(low_cardinality_keys256_two_level) \
         M(low_cardinality_key_string_two_level) \
-        M(low_cardinality_key_fixed_string_two_level) \
+        M(low_cardinality_key_fixed_string_two_level)
 
-    bool isLowCardinality()
+    bool isLowCardinality() const
     {
         switch (type)
         {
@@ -972,7 +972,7 @@ public:
 
     /** Set a function that checks whether the current task can be aborted.
       */
-    void setCancellationHook(const CancellationHook cancellation_hook);
+    void setCancellationHook(const CancellationHook & cancellation_hook);
 
     /// For external aggregation.
     void writeToTemporaryFile(AggregatedDataVariants & data_variants, const String & tmp_path);
diff --git a/src/Interpreters/ExpressionActions.cpp b/src/Interpreters/ExpressionActions.cpp
index f0dcf830c82..13daf52f5fc 100644
--- a/src/Interpreters/ExpressionActions.cpp
+++ b/src/Interpreters/ExpressionActions.cpp
@@ -67,7 +67,7 @@ ExpressionActionsPtr ExpressionActions::clone() const
 
 void ExpressionActions::linearizeActions()
 {
-    /// This function does the topological sort or DAG and fills all the fields of ExpressionActions.
+    /// This function does the topological sort on DAG and fills all the fields of ExpressionActions.
     /// Algorithm traverses DAG starting from nodes without children.
     /// For every node we support the number of created children, and if all children are created, put node into queue.
     struct Data
diff --git a/src/Processors/Executors/PipelineExecutor.cpp b/src/Processors/Executors/PipelineExecutor.cpp
index 1646a1a01fe..6192828784f 100644
--- a/src/Processors/Executors/PipelineExecutor.cpp
+++ b/src/Processors/Executors/PipelineExecutor.cpp
@@ -491,7 +491,7 @@ void PipelineExecutor::executeStepImpl(size_t thread_num, size_t num_threads, st
     while (!finished && !yield)
     {
         /// First, find any processor to execute.
-        /// Just travers graph and prepare any processor.
+        /// Just traverse graph and prepare any processor.
         while (!finished && node == nullptr)
         {
             {
diff --git a/src/Processors/IProcessor.h b/src/Processors/IProcessor.h
index c3abe40c3b7..ffdb363663d 100644
--- a/src/Processors/IProcessor.h
+++ b/src/Processors/IProcessor.h
@@ -249,7 +249,7 @@ public:
     UInt64 getInputPortNumber(const InputPort * input_port) const
     {
         UInt64 number = 0;
-        for (auto & port : inputs)
+        for (const auto & port : inputs)
         {
             if (&port == input_port)
                 return number;
@@ -263,7 +263,7 @@ public:
     UInt64 getOutputPortNumber(const OutputPort * output_port) const
     {
         UInt64 number = 0;
-        for (auto & port : outputs)
+        for (const auto & port : outputs)
         {
             if (&port == output_port)
                 return number;