code: public String deleteByExample(MappedStatement ms) {
          Class<?> entityClass = getEntityClass(ms);
          StringBuilder sql = new StringBuilder();
          if (isCheckExampleEntityClass()) {
              sql.append(SqlHelper.exampleCheck(entityClass));
          }
          //如果设置了安全删除，就不允许执行不带查询条件的 delete 方法
          if (getConfig().isSafeDelete()) {
              sql.append(SqlHelper.exampleHasAtLeastOneCriteriaCheck("_parameter"));
          }
          if (SqlHelper.hasLogicDeleteColumn(entityClass)) {
              sql.append(SqlHelper.updateTable(entityClass, tableName(entityClass)));
              sql.append("<set>");
              sql.append(SqlHelper.logicDeleteColumnEqualsValue(entityClass, true));
              sql.append("</set>");
              MetaObjectUtil.forObject(ms).setValue("sqlCommandType", SqlCommandType.UPDATE);
          } else {
              sql.append(SqlHelper.deleteFromTable(entityClass, tableName(entityClass)));
          }
          sql.append(SqlHelper.exampleWhereClause());
          return sql.toString();
      }
docs: 根据Example删除
  
  @param ms
  @return