comment

dbms/src/DataStreams/ParallelParsingBlockInputStream.cpp

@@ -15,7 +15,7 @@ void ParallelParsingBlockInputStream::segmentatorThreadFunction()
 
             {
                 std::unique_lock lock(mutex);
-                segmentator_condvar.wait(lock, [&]{ return status[current_unit_number] == READY_TO_INSERT || is_exception_occured || is_cancelled || executed; });
+                segmentator_condvar.wait(lock, [&]{ return status[current_unit_number] == READY_TO_INSERT || is_exception_occured || executed; });
             }
 
             if (is_exception_occured)
@@ -119,7 +119,7 @@ Block ParallelParsingBlockInputStream::readImpl()
 
     std::unique_lock lock(mutex);
     const auto current_number = reader_ticket_number % max_threads_to_use;
-    reader_condvar.wait(lock, [&](){ return status[current_number] == READY_TO_READ || is_exception_occured || is_cancelled || executed; });
+    reader_condvar.wait(lock, [&](){ return status[current_number] == READY_TO_READ || is_exception_occured || executed; });
 
     /// Check for an exception and rethrow it
     if (is_exception_occured)

dbms/src/DataStreams/ParallelParsingBlockInputStream.h

@@ -100,6 +100,8 @@ public:
         if (!is_cancelled.compare_exchange_strong(old_val, true))
             return;
 
+        executed = true;
+
         for (auto& reader: readers)
             if (!reader->isCancelled())
                 reader->cancel(kill);

dbms/src/IO/ReadHelpers.h

@@ -914,6 +914,14 @@ void skipToUnescapedNextLineOrEOF(ReadBuffer & buf);
 
 /** Returns buffer eof() result.
   * And saves data if there is no pending data in buffer or it was explicitly asked.
+  * Why we have to use this strange function? Consider we have begin_pos in the middle of our buffer
+  * and the cursor in the end of the buffer. When we call eof() it calls next().
+  * And this function can fill the buffer with new data, so we will lose the data from previous buffer state.
+  * @param buf - original buffer to read from.
+  *        memory - where to put data from buf
+  *        used_size - special parameter not to do useless reallocations
+  *        begin_pos - defines from which position we will copy the data.
+  *        forse_saving_buffer_state - allows to explicitly copy all the data from begin_pos to current_position.
   */
 bool eofWithSavingBufferState(ReadBuffer & buf, DB::Memory<> & memory, size_t & used_size, char * & begin_pos, bool force_saving_buffer_state = false);