diff --git a/src/Disks/S3/DiskS3.cpp b/src/Disks/S3/DiskS3.cpp
index 42c022a3714..3d91d5fbb78 100644
--- a/src/Disks/S3/DiskS3.cpp
+++ b/src/Disks/S3/DiskS3.cpp
@@ -249,7 +249,7 @@ public:
         if (whence == SEEK_CUR)
         {
             /// If position within current working buffer - shift pos.
-            if (working_buffer.size() && size_t(getPosition() + offset_) < absolute_position)
+            if (!working_buffer.empty() && size_t(getPosition() + offset_) < absolute_position)
             {
                 pos += offset_;
                 return getPosition();
@@ -262,7 +262,7 @@ public:
         else if (whence == SEEK_SET)
         {
             /// If position within current working buffer - shift pos.
-            if (working_buffer.size() && size_t(offset_) >= absolute_position - working_buffer.size()
+            if (!working_buffer.empty() && size_t(offset_) >= absolute_position - working_buffer.size()
                 && size_t(offset_) < absolute_position)
             {
                 pos = working_buffer.end() - (absolute_position - offset_);
diff --git a/src/IO/BrotliReadBuffer.cpp b/src/IO/BrotliReadBuffer.cpp
index 70d3a76e629..41991ad0516 100644
--- a/src/IO/BrotliReadBuffer.cpp
+++ b/src/IO/BrotliReadBuffer.cpp
@@ -77,7 +77,7 @@ bool BrotliReadBuffer::nextImpl()
         if (in->eof())
         {
             eof = true;
-            return working_buffer.size() != 0;
+            return !working_buffer.empty();
         }
         else
         {
diff --git a/src/IO/BufferBase.h b/src/IO/BufferBase.h
index c22dcbecf7b..198441d8bc1 100644
--- a/src/IO/BufferBase.h
+++ b/src/IO/BufferBase.h
@@ -40,6 +40,7 @@ public:
         inline Position end() const { return end_pos; }
         inline size_t size() const { return size_t(end_pos - begin_pos); }
         inline void resize(size_t size) { end_pos = begin_pos + size; }
+        inline bool empty() const { return size() == 0; }
 
         inline void swap(Buffer & other)
         {
diff --git a/src/IO/ConcatReadBuffer.h b/src/IO/ConcatReadBuffer.h
index 1df99429e93..c416b0fd892 100644
--- a/src/IO/ConcatReadBuffer.h
+++ b/src/IO/ConcatReadBuffer.h
@@ -25,11 +25,16 @@ protected:
             return false;
 
         /// First reading
-        if (working_buffer.size() == 0 && (*current)->hasPendingData())
+        if (working_buffer.empty())
         {
-            working_buffer = Buffer((*current)->position(), (*current)->buffer().end());
-            return true;
+            if ((*current)->hasPendingData())
+            {
+                working_buffer = Buffer((*current)->position(), (*current)->buffer().end());
+                return true;
+            }
         }
+        else
+            (*current)->position() = position();
 
         if (!(*current)->next())
         {
@@ -51,14 +56,12 @@ protected:
     }
 
 public:
-    ConcatReadBuffer(const ReadBuffers & buffers_) : ReadBuffer(nullptr, 0), buffers(buffers_), current(buffers.begin()) {}
-
-    ConcatReadBuffer(ReadBuffer & buf1, ReadBuffer & buf2) : ReadBuffer(nullptr, 0)
+    explicit ConcatReadBuffer(const ReadBuffers & buffers_) : ReadBuffer(nullptr, 0), buffers(buffers_), current(buffers.begin())
     {
-        buffers.push_back(&buf1);
-        buffers.push_back(&buf2);
-        current = buffers.begin();
+        assert(!buffers.empty());
     }
+
+    ConcatReadBuffer(ReadBuffer & buf1, ReadBuffer & buf2) : ConcatReadBuffer({&buf1, &buf2}) {}
 };
 
 }
diff --git a/src/IO/HashingReadBuffer.h b/src/IO/HashingReadBuffer.h
index 9fcd6dc6b41..08b6de69dcb 100644
--- a/src/IO/HashingReadBuffer.h
+++ b/src/IO/HashingReadBuffer.h
@@ -1,10 +1,11 @@
 #pragma once
 
-#include <IO/ReadBuffer.h>
 #include <IO/HashingWriteBuffer.h>
+#include <IO/ReadBuffer.h>
 
 namespace DB
 {
+
 /*
  * Calculates the hash from the read data. When reading, the data is read from the nested ReadBuffer.
  * Small pieces are copied into its own memory.
@@ -12,14 +13,14 @@ namespace DB
 class HashingReadBuffer : public IHashingBuffer<ReadBuffer>
 {
 public:
-    HashingReadBuffer(ReadBuffer & in_, size_t block_size_ = DBMS_DEFAULT_HASHING_BLOCK_SIZE) :
-        IHashingBuffer<ReadBuffer>(block_size_), in(in_)
+    explicit HashingReadBuffer(ReadBuffer & in_, size_t block_size_ = DBMS_DEFAULT_HASHING_BLOCK_SIZE)
+        : IHashingBuffer<ReadBuffer>(block_size_), in(in_)
     {
         working_buffer = in.buffer();
         pos = in.position();
 
         /// calculate hash from the data already read
-        if (working_buffer.size())
+        if (!working_buffer.empty())
         {
             calculateHash(pos, working_buffer.end() - pos);
         }
@@ -39,7 +40,7 @@ private:
         return res;
     }
 
-private:
     ReadBuffer & in;
 };
+
 }
diff --git a/src/IO/LZMAInflatingReadBuffer.cpp b/src/IO/LZMAInflatingReadBuffer.cpp
index e30e8df5f9d..6a0a7e5ee31 100644
--- a/src/IO/LZMAInflatingReadBuffer.cpp
+++ b/src/IO/LZMAInflatingReadBuffer.cpp
@@ -66,7 +66,7 @@ bool LZMAInflatingReadBuffer::nextImpl()
         if (in->eof())
         {
             eof = true;
-            return working_buffer.size() != 0;
+            return !working_buffer.empty();
         }
         else
         {
diff --git a/src/IO/LimitReadBuffer.cpp b/src/IO/LimitReadBuffer.cpp
index f36facfdd99..b0d734c9ca0 100644
--- a/src/IO/LimitReadBuffer.cpp
+++ b/src/IO/LimitReadBuffer.cpp
@@ -50,7 +50,7 @@ LimitReadBuffer::LimitReadBuffer(ReadBuffer & in_, UInt64 limit_, bool throw_exc
 LimitReadBuffer::~LimitReadBuffer()
 {
     /// Update underlying buffer's position in case when limit wasn't reached.
-    if (working_buffer.size() != 0)
+    if (!working_buffer.empty())
         in.position() = position();
 }
 
diff --git a/src/IO/MemoryReadWriteBuffer.cpp b/src/IO/MemoryReadWriteBuffer.cpp
index 0b0d9704de6..69bcd52a8d2 100644
--- a/src/IO/MemoryReadWriteBuffer.cpp
+++ b/src/IO/MemoryReadWriteBuffer.cpp
@@ -61,7 +61,7 @@ private:
             position() = nullptr;
         }
 
-        return buffer().size() != 0;
+        return !buffer().empty();
     }
 
     using Container = std::forward_list<BufferBase::Buffer>;
diff --git a/src/IO/ReadBuffer.h b/src/IO/ReadBuffer.h
index 68ebf154597..e871205aef3 100644
--- a/src/IO/ReadBuffer.h
+++ b/src/IO/ReadBuffer.h
@@ -55,6 +55,7 @@ public:
       */
     bool next()
     {
+        assert(!hasPendingData());
         assert(position() <= working_buffer.end());
 
         bytes += offset();
@@ -77,7 +78,7 @@ public:
             next();
     }
 
-    virtual ~ReadBuffer() {}
+    virtual ~ReadBuffer() = default;
 
 
     /** Unlike std::istream, it returns true if all data was read
@@ -197,7 +198,7 @@ private:
       */
     virtual bool nextImpl() { return false; }
 
-    [[noreturn]] void throwReadAfterEOF()
+    [[noreturn]] static void throwReadAfterEOF()
     {
         throw Exception("Attempt to read after eof", ErrorCodes::ATTEMPT_TO_READ_AFTER_EOF);
     }
diff --git a/src/IO/ReadWriteBufferFromHTTP.h b/src/IO/ReadWriteBufferFromHTTP.h
index de10f268dc3..9cd37bd00f8 100644
--- a/src/IO/ReadWriteBufferFromHTTP.h
+++ b/src/IO/ReadWriteBufferFromHTTP.h
@@ -76,9 +76,7 @@ public:
         }
     }
 
-    virtual ~UpdatableSessionBase()
-    {
-    }
+    virtual ~UpdatableSessionBase() = default;
 };
 
 
@@ -205,6 +203,8 @@ namespace detail
         {
             if (next_callback)
                 next_callback(count());
+            if (!working_buffer.empty())
+                impl->position() = position();
             if (!impl->next())
                 return false;
             internal_buffer = impl->buffer();
diff --git a/src/IO/WriteBuffer.h b/src/IO/WriteBuffer.h
index 6abcc1c8eed..d425f813d7b 100644
--- a/src/IO/WriteBuffer.h
+++ b/src/IO/WriteBuffer.h
@@ -61,7 +61,7 @@ public:
     /** it is desirable in the derived classes to place the next() call in the destructor,
       * so that the last data is written
       */
-    virtual ~WriteBuffer() {}
+    virtual ~WriteBuffer() = default;
 
     inline void nextIfAtEnd()
     {
@@ -75,7 +75,7 @@ public:
         size_t bytes_copied = 0;
 
         /// Produces endless loop
-        assert(working_buffer.size() > 0);
+        assert(!working_buffer.empty());
 
         while (bytes_copied < n)
         {
diff --git a/src/IO/ZlibInflatingReadBuffer.cpp b/src/IO/ZlibInflatingReadBuffer.cpp
index 0b23bef1b10..bea83c74e21 100644
--- a/src/IO/ZlibInflatingReadBuffer.cpp
+++ b/src/IO/ZlibInflatingReadBuffer.cpp
@@ -70,7 +70,7 @@ bool ZlibInflatingReadBuffer::nextImpl()
         if (in->eof())
         {
             eof = true;
-            return working_buffer.size() != 0;
+            return !working_buffer.empty();
         }
         else
         {
diff --git a/src/IO/ZstdInflatingReadBuffer.cpp b/src/IO/ZstdInflatingReadBuffer.cpp
index 94a0b56fc6d..b441a6a7210 100644
--- a/src/IO/ZstdInflatingReadBuffer.cpp
+++ b/src/IO/ZstdInflatingReadBuffer.cpp
@@ -54,7 +54,7 @@ bool ZstdInflatingReadBuffer::nextImpl()
     if (in->eof())
     {
         eof = true;
-        return working_buffer.size() != 0;
+        return !working_buffer.empty();
     }
 
     return true;
diff --git a/src/Server/HTTPHandler.cpp b/src/Server/HTTPHandler.cpp
index e161b5752ae..5e0d1f0ac66 100644
--- a/src/Server/HTTPHandler.cpp
+++ b/src/Server/HTTPHandler.cpp
@@ -219,8 +219,11 @@ void HTTPHandler::pushDelayedResults(Output & used_output)
         }
     }
 
-    ConcatReadBuffer concat_read_buffer(read_buffers_raw_ptr);
-    copyData(concat_read_buffer, *used_output.out_maybe_compressed);
+    if (!read_buffers_raw_ptr.empty())
+    {
+        ConcatReadBuffer concat_read_buffer(read_buffers_raw_ptr);
+        copyData(concat_read_buffer, *used_output.out_maybe_compressed);
+    }
 }