1 files changed, 61 insertions, 0 deletions
diff --git a/src/backend/utils/adt/numeric.c b/src/backend/utils/adt/numeric.c
index 682200f636b..9525ade1f7c 100644
--- a/src/backend/utils/adt/numeric.c
+++ b/src/backend/utils/adt/numeric.c
@@ -4092,6 +4092,67 @@ int64_to_numeric(int64 val)
 	return res;
 }
 
+/*
+ * Convert val1/(10**val2) to numeric.  This is much faster than normal
+ * numeric division.
+ */
+Numeric
+int64_div_fast_to_numeric(int64 val1, int log10val2)
+{
+	Numeric		res;
+	NumericVar	result;
+	int64		saved_val1 = val1;
+	int			w;
+	int			m;
+
+	/* how much to decrease the weight by */
+	w = log10val2 / DEC_DIGITS;
+	/* how much is left */
+	m = log10val2 % DEC_DIGITS;
+
+	/*
+	 * If there is anything left, multiply the dividend by what's left, then
+	 * shift the weight by one more.
+	 */
+	if (m > 0)
+	{
+		static int	pow10[] = {1, 10, 100, 1000};
+
+		StaticAssertStmt(lengthof(pow10) == DEC_DIGITS, "mismatch with DEC_DIGITS");
+		if (unlikely(pg_mul_s64_overflow(val1, pow10[DEC_DIGITS - m], &val1)))
+		{
+			/*
+			 * If it doesn't fit, do the whole computation in numeric the slow
+			 * way.  Note that va1l may have been overwritten, so use
+			 * saved_val1 instead.
+			 */
+			int			val2 = 1;
+
+			for (int i = 0; i < log10val2; i++)
+				val2 *= 10;
+			res = numeric_div_opt_error(int64_to_numeric(saved_val1), int64_to_numeric(val2), NULL);
+			res = DatumGetNumeric(DirectFunctionCall2(numeric_round,
+													  NumericGetDatum(res),
+													  Int32GetDatum(log10val2)));
+			return res;
+		}
+		w++;
+	}
+
+	init_var(&result);
+
+	int64_to_numericvar(val1, &result);
+
+	result.weight -= w;
+	result.dscale += w * DEC_DIGITS - (DEC_DIGITS - m);
+
+	res = make_result(&result);
+
+	free_var(&result);
+
+	return res;
+}
+
 Datum
 int4_numeric(PG_FUNCTION_ARGS)
 {