feat(query): add diff function scalar version

include/libs/scalar/scalar.h

@@ -113,6 +113,7 @@ int32_t twaScalarFunction(SScalarParam *pInput, int32_t inputNum, SScalarParam *
 int32_t mavgScalarFunction(SScalarParam *pInput, int32_t inputNum, SScalarParam *pOutput);
 int32_t hllScalarFunction(SScalarParam *pInput, int32_t inputNum, SScalarParam *pOutput);
 int32_t csumScalarFunction(SScalarParam *pInput, int32_t inputNum, SScalarParam *pOutput);
+int32_t diffScalarFunction(SScalarParam *pInput, int32_t inputNum, SScalarParam *pOutput);
 
 #ifdef __cplusplus
 }

source/libs/function/src/builtins.c

@@ -2408,6 +2408,7 @@ const SBuiltinFuncDefinition funcMgtBuiltins[] = {
     .getEnvFunc   = getDiffFuncEnv,
     .initFunc     = diffFunctionSetup,
     .processFunc  = diffFunction,
+    .sprocessFunc = diffScalarFunction,
     .finalizeFunc = functionFinalize
   },
   {

source/libs/scalar/src/sclfunc.c

@@ -2408,6 +2408,10 @@ int32_t irateScalarFunction(SScalarParam *pInput, int32_t inputNum, SScalarParam
   return nonCalcScalarFunction(pInput, inputNum, pOutput);
 }
 
+int32_t diffScalarFunction(SScalarParam *pInput, int32_t inputNum, SScalarParam *pOutput) {
+  return nonCalcScalarFunction(pInput, inputNum, pOutput);
+}
+
 int32_t twaScalarFunction(SScalarParam *pInput, int32_t inputNum, SScalarParam *pOutput) {
   return avgScalarFunction(pInput, inputNum, pOutput);
 }