I am also a graduate student majoring in computer science, and my postgraduate direction is data mining. In fact, the requirements for mathematics depend on the direction you want to go after graduation. If it is a data warehouse, it is based on strong database knowledge and modeling (requires business knowledge). If we want to take the algorithm, that is, the algorithm of data mining, we need mathematics, and the tools of data mining, SPSS and SAS, are almost all statistical algorithms. Personal advice can take the route of data warehouse and learn more databases.