Added avg for half vectors [skip ci]

src/halfvec.c

@@ -23,6 +23,9 @@
 #define TYPALIGN_INT 'i'
 #endif
 
+#define STATE_DIMS(x) (ARR_DIMS(x)[0] - 1)
+#define CreateStateDatums(dim) palloc(sizeof(Datum) * (dim + 1))
+
 /*
  * Get a half from a message buffer
  */
@@ -146,6 +149,20 @@ halfvec_isspace(char ch)
 	return false;
 }
 
+/*
+ * Check state array
+ */
+static float8 *
+CheckStateArray(ArrayType *statearray, const char *caller)
+{
+	if (ARR_NDIM(statearray) != 1 ||
+		ARR_DIMS(statearray)[0] < 1 ||
+		ARR_HASNULL(statearray) ||
+		ARR_ELEMTYPE(statearray) != FLOAT8OID)
+		elog(ERROR, "%s: expected state array", caller);
+	return (float8 *) ARR_DATA_PTR(statearray);
+}
+
 #if PG_VERSION_NUM < 120003
 static pg_noinline void
 float_overflow_error(void)
@@ -1016,3 +1033,98 @@ halfvec_cmp(PG_FUNCTION_ARGS)
 
 	PG_RETURN_INT32(halfvec_cmp_internal(a, b));
 }
+
+/*
+ * Accumulate half vectors
+ */
+PGDLLEXPORT PG_FUNCTION_INFO_V1(halfvec_accum);
+Datum
+halfvec_accum(PG_FUNCTION_ARGS)
+{
+	ArrayType  *statearray = PG_GETARG_ARRAYTYPE_P(0);
+	HalfVector *newval = PG_GETARG_HALFVEC_P(1);
+	float8	   *statevalues;
+	int16		dim;
+	bool		newarr;
+	float8		n;
+	Datum	   *statedatums;
+	half	   *x = newval->x;
+	ArrayType  *result;
+
+	/* Check array before using */
+	statevalues = CheckStateArray(statearray, "halfvec_accum");
+	dim = STATE_DIMS(statearray);
+	newarr = dim == 0;
+
+	if (newarr)
+		dim = newval->dim;
+	else
+		CheckExpectedDim(dim, newval->dim);
+
+	n = statevalues[0] + 1.0;
+
+	statedatums = CreateStateDatums(dim);
+	statedatums[0] = Float8GetDatum(n);
+
+	if (newarr)
+	{
+		for (int i = 0; i < dim; i++)
+			statedatums[i + 1] = Float8GetDatum((double) HalfToFloat4(x[i]));
+	}
+	else
+	{
+		for (int i = 0; i < dim; i++)
+		{
+			double		v = statevalues[i + 1] + (double) HalfToFloat4(x[i]);
+
+			/* Check for overflow */
+			if (isinf(v))
+				float_overflow_error();
+
+			statedatums[i + 1] = Float8GetDatum(v);
+		}
+	}
+
+	/* Use float8 array like float4_accum */
+	result = construct_array(statedatums, dim + 1,
+							 FLOAT8OID,
+							 sizeof(float8), FLOAT8PASSBYVAL, TYPALIGN_DOUBLE);
+
+	pfree(statedatums);
+
+	PG_RETURN_ARRAYTYPE_P(result);
+}
+
+/*
+ * Average half vectors
+ */
+PGDLLEXPORT PG_FUNCTION_INFO_V1(halfvec_avg);
+Datum
+halfvec_avg(PG_FUNCTION_ARGS)
+{
+	ArrayType  *statearray = PG_GETARG_ARRAYTYPE_P(0);
+	float8	   *statevalues;
+	float8		n;
+	uint16		dim;
+	HalfVector *result;
+
+	/* Check array before using */
+	statevalues = CheckStateArray(statearray, "halfvec_avg");
+	n = statevalues[0];
+
+	/* SQL defines AVG of no values to be NULL */
+	if (n == 0.0)
+		PG_RETURN_NULL();
+
+	/* Create half vector */
+	dim = STATE_DIMS(statearray);
+	CheckDim(dim);
+	result = InitHalfVector(dim);
+	for (int i = 0; i < dim; i++)
+	{
+		result->x[i] = Float4ToHalf(statevalues[i + 1] / n);
+		CheckElement(result->x[i]);
+	}
+
+	PG_RETURN_POINTER(result);
+}

src/vector.c

@@ -1100,7 +1100,7 @@ vector_accum(PG_FUNCTION_ARGS)
 }
 
 /*
- * Combine vectors
+ * Combine vectors or half vectors
  */
 PGDLLEXPORT PG_FUNCTION_INFO_V1(vector_combine);
 Datum