Fix numeric modulo operator for case of fractional right argument.

diff --git a/src/backend/utils/adt/numeric.c b/src/backend/utils/adt/numeric.c
index 3eb733c6d71d242895155d0cc93c3bbf249e9132..d18d3003a0888bdf35e196b08554d167d757ff41 100644 (file)
--- a/src/backend/utils/adt/numeric.c
+++ b/src/backend/utils/adt/numeric.c
@@ -5,7 +5,7 @@
  *
  * 1998 Jan Wieck
  *
- * $Header: /cvsroot/pgsql/src/backend/utils/adt/numeric.c,v 1.36 2000/12/07 02:47:35 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/utils/adt/numeric.c,v 1.37 2001/03/14 16:50:37 tgl Exp $
  *
  * ----------
  */
@@ -3355,16 +3355,19 @@ mod_var(NumericVar *var1, NumericVar *var2, NumericVar *result)
    init_var(&tmp);
 
    /* ----------
-    * We do it by fiddling around with global_rscale and truncating
-    * the result of the division.
+    * We do this using the equation
+    *      mod(x,y) = x - trunc(x/y)*y
+    * We fiddle a bit with global_rscale to control result precision.
     * ----------
     */
    save_global_rscale = global_rscale;
    global_rscale = var2->rscale + 2;
 
    div_var(var1, var2, &tmp);
+
+   /* do trunc() by forgetting digits to the right of the decimal point */
+   tmp.ndigits = MAX(0, MIN(tmp.ndigits, tmp.weight + 1));
    tmp.rscale = var2->rscale;
-   tmp.ndigits = MAX(0, MIN(tmp.ndigits, tmp.weight + tmp.rscale + 1));
 
    global_rscale = var2->rscale;
    mul_var(var2, &tmp, &tmp);