Refactor utility function to be used by both SUM and AVG Aggregates (y…

…ugabyte#82)

Description
Refactor the previously introduced helper function into a common utility (bigint_utility) function which can be used by both SUM and AVG aggregates for BIGINT datatype

Issues Resolved
BABEL-3507

Extension PR
babelfish-for-postgresql/babelfish_extensions#1045

Signed-off-by: Nirmit Shah nirmisha@amazon.com

src/postgres/src/backend/utils/adt/numeric.c

@@ -5941,8 +5941,14 @@ numeric_poly_sum(PG_FUNCTION_ARGS)
 #endif
 }
 
+/*
+ *	Final function for BIGINT datatype for TSQL Aggregates (SUM,AVG).
+ *  The tsql aggregate return non-default return types when compared with 
+ *  Default aggregate for integer datatypes , this function takes the accumlated
+ *  State and tranform the result into return type expected by tsql.
+ */
 Datum
-bigint_poly_sum(PG_FUNCTION_ARGS)
+bigint_poly_aggr_final(FunctionCallInfo fcinfo, tsqlAggType aggType)
 {
 
 	PolyNumAggState		*state;
@@ -5969,10 +5975,23 @@ bigint_poly_sum(PG_FUNCTION_ARGS)
 					(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
 						errmsg("Arithmetic overflow error converting expression to data type bigint.")));
 		}
-		else
-			PG_RETURN_INT64((int64) result);
+		else {
+			if (aggType == TSQL_SUM)
+				PG_RETURN_INT64((int64) result);
+			/* If the aggregate type is TSQL_AVG */
+			else
+			{
+				result /= state->N;
+				PG_RETURN_INT64((int64) result);
+			}
+		}
 	#else
-		temp = numeric_sum(fcinfo);
+		if (tsqlAggType == TSQL_SUM)
+			temp = numeric_sum(fcinfo);
+		/* If the aggregate type is TSQL_AVG */
+		else
+			temp = numeric_avg(fcinfo);
+
 		init_var(&nvar);
 		set_var_from_num(DatumGetNumeric(temp), &nvar);
 		is_overflow = !(numericvar_to_int64(&nvar, &result));

src/postgres/src/include/utils/numeric.h

@@ -53,6 +53,12 @@
 struct NumericData;
 typedef struct NumericData *Numeric;
 
+/* Enum type for bigint aggregates for tsql dialect */
+typedef enum tsqlAggType {
+	TSQL_SUM,
+	TSQL_AVG
+} tsqlAggType;
+
 /*
  * fmgr interface macros
  */
@@ -95,7 +101,7 @@ extern Numeric numeric_mod_opt_error(Numeric num1, Numeric num2,
 									 bool *have_error);
 extern int32 numeric_int4_opt_error(Numeric num, bool *error);
 
-extern Datum bigint_poly_sum(PG_FUNCTION_ARGS);
+extern Datum bigint_poly_aggr_final(FunctionCallInfo fcinfo, tsqlAggType aggType);
 
 /* Hook interface to calculate exact numeric digits before generating numeric overflow error in TSQL */
 typedef bool (*detect_numeric_overflow_hook_type) (int weight, int dscale, int first_block, int numeric_base);