Fix zerofill double calc hash inconsistent

src/sql/engine/expr/ob_expr_cast.cpp

@@ -743,7 +743,10 @@ int ObExprCast::cg_expr(ObExprCGCtx &op_cg_ctx,
         if (OB_UNLIKELY(UINT_MAX8 < src_res_type.get_length())) {
           ret = OB_ERR_UNEXPECTED;
           LOG_WARN("unexpected zerofill length", K(ret), K(src_res_type.get_length()));
-        } else {
+        } else if (ob_is_string_or_lob_type(out_type)) {
+          // The zerofill information will only be used when cast to string/lob type.
+          // for these types, scale is unused, so the previous design is to save child length
+          // to the scale of the rt_expr.
           rt_expr.datum_meta_.scale_ = static_cast<int8_t>(src_res_type.get_length());
         }
       }