diff --git a/dbms/src/Common/CompactArray.h b/dbms/src/Common/CompactArray.h
index 3cd47b8013e..5a948b57059 100644
--- a/dbms/src/Common/CompactArray.h
+++ b/dbms/src/Common/CompactArray.h
@@ -86,7 +86,7 @@ template <typename BucketIndex, UInt8 content_width, size_t bucket_count>
 class CompactArray<BucketIndex, content_width, bucket_count>::Reader final
 {
 public:
-    Reader(ReadBuffer & in_)
+    explicit Reader(ReadBuffer & in_)
         : in(in_)
     {
     }
@@ -177,7 +177,7 @@ class CompactArray<BucketIndex, content_width, bucket_count>::Locus final
     friend class CompactArray::Reader;
 
 public:
-    ALWAYS_INLINE operator UInt8() const
+    ALWAYS_INLINE explicit operator UInt8() const
     {
         if (content_l == content_r)
             return read(*content_l);
@@ -211,7 +211,7 @@ class CompactArray<BucketIndex, content_width, bucket_count>::Locus final
 private:
     Locus() = default;
 
-    Locus(BucketIndex bucket_index)
+    explicit Locus(BucketIndex bucket_index)
     {
         init(bucket_index);
     }
diff --git a/dbms/src/Common/ConcurrentBoundedQueue.h b/dbms/src/Common/ConcurrentBoundedQueue.h
index d8c63fb51a1..378ea35bde1 100644
--- a/dbms/src/Common/ConcurrentBoundedQueue.h
+++ b/dbms/src/Common/ConcurrentBoundedQueue.h
@@ -52,7 +52,7 @@ class ConcurrentBoundedQueue
     Poco::Semaphore empty_count;
 
 public:
-    ConcurrentBoundedQueue(size_t max_fill)
+    explicit ConcurrentBoundedQueue(size_t max_fill)
         : fill_count(0, max_fill)
         , empty_count(max_fill, max_fill)
     {}
diff --git a/dbms/src/Common/Config/ConfigReloader.cpp b/dbms/src/Common/Config/ConfigReloader.cpp
index fd6a1ab1fc8..749947800dc 100644
--- a/dbms/src/Common/Config/ConfigReloader.cpp
+++ b/dbms/src/Common/Config/ConfigReloader.cpp
@@ -132,7 +132,7 @@ void ConfigReloader::FilesChangesTracker::addIfExists(const std::string & path)
     }
 }
 
-bool ConfigReloader::FilesChangesTracker::isDifferOrNewerThan(const FilesChangesTracker & rhs)
+bool ConfigReloader::FilesChangesTracker::isDifferOrNewerThan(const FilesChangesTracker & rhs) const
 {
     return (files.size() != rhs.files.size()) || !std::equal(files.begin(), files.end(), rhs.files.begin(), FileWithTimestamp::isTheSame);
 }
diff --git a/dbms/src/Common/Config/ConfigReloader.h b/dbms/src/Common/Config/ConfigReloader.h
index 3aee3640c63..a5995f60387 100644
--- a/dbms/src/Common/Config/ConfigReloader.h
+++ b/dbms/src/Common/Config/ConfigReloader.h
@@ -45,7 +45,7 @@ class ConfigReloader
     void reload() { reloadIfNewer(/* force */ true, /* throw_on_error */ true); }
 
 protected:
-    virtual void reloadIfNewer(bool force, bool throw_on_error);
+    void reloadIfNewer(bool force, bool throw_on_error);
     Updater & getUpdater() { return updater; }
 
 private:
@@ -58,7 +58,7 @@ class ConfigReloader
         std::set<FileWithTimestamp> files;
 
         void addIfExists(const std::string & path);
-        bool isDifferOrNewerThan(const FilesChangesTracker & rhs);
+        bool isDifferOrNewerThan(const FilesChangesTracker & rhs) const;
     };
 
     FilesChangesTracker getNewFileList() const;
diff --git a/dbms/src/Common/Config/TOMLConfiguration.cpp b/dbms/src/Common/Config/TOMLConfiguration.cpp
index 52b459e7599..58124f4fd32 100644
--- a/dbms/src/Common/Config/TOMLConfiguration.cpp
+++ b/dbms/src/Common/Config/TOMLConfiguration.cpp
@@ -50,7 +50,7 @@ bool TOMLConfiguration::getRaw(const std::string & key, std::string & value) con
     }
 }
 
-bool TOMLConfiguration::find_parent(const std::string & key, TOMLTablePtr & parent, std::string & child_key)
+bool TOMLConfiguration::findParent(const std::string & key, TOMLTablePtr & parent, std::string & child_key)
 {
     auto pos = key.find_last_of('.');
 
@@ -85,7 +85,7 @@ void TOMLConfiguration::setRaw(const std::string & key, const std::string & valu
 {
     TOMLTablePtr parent;
     std::string child_key;
-    if (!find_parent(key, parent, child_key))
+    if (!findParent(key, parent, child_key))
         throw Poco::NotFoundException("Key not found in TOML configuration", key);
 
     parent->erase(child_key);
@@ -100,8 +100,8 @@ void TOMLConfiguration::enumerate(const std::string & key, Keys & range) const
     if (!table)
         return;
 
-    for (auto it = table->begin(); it != table->end(); it++)
-        range.push_back(it->first);
+    for (const auto & it : *table)
+        range.push_back(it.first);
 }
 
 void TOMLConfiguration::removeRaw(const std::string & key)
@@ -109,7 +109,7 @@ void TOMLConfiguration::removeRaw(const std::string & key)
     TOMLTablePtr parent;
     std::string child_key;
 
-    if (find_parent(key, parent, child_key))
+    if (findParent(key, parent, child_key))
         parent->erase(child_key);
 }
 
diff --git a/dbms/src/Common/Config/TOMLConfiguration.h b/dbms/src/Common/Config/TOMLConfiguration.h
index c4c3ee2989d..5026f32170c 100644
--- a/dbms/src/Common/Config/TOMLConfiguration.h
+++ b/dbms/src/Common/Config/TOMLConfiguration.h
@@ -16,7 +16,7 @@ using TOMLTablePtr = std::shared_ptr<cpptoml::table>;
 class TOMLConfiguration : public Poco::Util::AbstractConfiguration
 {
 public:
-    TOMLConfiguration(TOMLTablePtr toml_doc);
+    explicit TOMLConfiguration(TOMLTablePtr toml_doc);
 
 protected:
     bool getRaw(const std::string & key, std::string & value) const;
@@ -36,7 +36,7 @@ class TOMLConfiguration : public Poco::Util::AbstractConfiguration
     /// Does nothing if the key does not exist.
 private:
     TOMLTablePtr root;
-    bool find_parent(const std::string & key, TOMLTablePtr & parent, std::string & child_key);
+    bool findParent(const std::string & key, TOMLTablePtr & parent, std::string & child_key);
 };
 
 } // namespace DB
diff --git a/dbms/src/Common/CurrentMetrics.h b/dbms/src/Common/CurrentMetrics.h
index 0d5d84d5a0e..e848c79ba5d 100644
--- a/dbms/src/Common/CurrentMetrics.h
+++ b/dbms/src/Common/CurrentMetrics.h
@@ -72,7 +72,7 @@ class Increment
     }
 
 public:
-    Increment(Metric metric, Value amount = 1)
+    explicit Increment(Metric metric, Value amount = 1)
         : Increment(&values[metric], amount)
     {}