Added function "sleepEachRow" for testing purposes #1713

dbms/src/Functions/FunctionsMiscellaneous.cpp

@@ -40,6 +40,7 @@ namespace ErrorCodes
     extern const int NUMBER_OF_ARGUMENTS_DOESNT_MATCH;
     extern const int FUNCTION_IS_SPECIAL;
     extern const int ARGUMENT_OUT_OF_BOUND;
+    extern const int TOO_SLOW;
 }
 
 /** Helper functions
@@ -624,7 +625,15 @@ public:
 
         /// We do not sleep if the block is empty.
         if (size > 0)
-            usleep(static_cast<unsigned>(seconds * (variant == FunctionSleepVariant::PerBlock ? 1 : size) * 1e6));
+        {
+            unsigned useconds = seconds * (variant == FunctionSleepVariant::PerBlock ? 1 : size) * 1e6;
+
+            /// When sleeping, the query cannot be cancelled. For abitily to cancel query, we limit sleep time.
+            if (useconds > 3000000)   /// The choice is arbitary
+                throw Exception("The maximum sleep time is 3000000 microseconds. Requested: " + toString(useconds), ErrorCodes::TOO_SLOW);
+
+            usleep(useconds);
+        }
 
         /// convertToFullColumn needed, because otherwise (constant expression case) function will not get called on each block.
         block.getByPosition(result).column = block.getByPosition(result).type->createColumnConst(size, UInt64(0))->convertToFullColumnIfConst();