Question

我想优化此SQL查询的性能。如果我使用一百万个密钥填充此哈希表，则查询将花费大约一分钟。我如何优化这种Java方法以加快执行速度？

private HashMap<String, Boolean> selectedIds = new HashMap<>();

public void deleteSelectedIDs() throws SQLException {

        if (ds == null) {
            throw new SQLException();
        }

        Connection conn = ds.getConnection();
        if (conn == null) {
            throw new SQLException();
        }

        PreparedStatement ps = null;
        ResultSet resultSet = null;

        try {
            conn.setAutoCommit(false);
            boolean committed = false;
            try {
                String sqlDeleteQuery = "DELETE FROM ACTIVESESSIONSLOG WHERE ASESSIONID = ?";

                Set<String> keySet = selectedIds.keySet();
                String[] keys = new String[]{};
                keys = selectedIds.keySet().toArray(keys);
                ps = conn.prepareStatement(sqlDeleteQuery);

                for (int i = 0; i < keys.length; i++) {
                    if (selectedIds.get(keys[i]).booleanValue()) {
                        ps.setString(1, keys[i]);
                        ps.executeUpdate();
                        ps.clearParameters();
                        selectedIds.put(keys[i], false); //get(keys[i]) = false;
                    }
                }

                conn.commit();
                committed = true;

                //selectedIds.clear();
            } finally {
                if (!committed) {
                    conn.rollback();
                }
            }
        } finally {
            ps.close();
            conn.close();
        }
    }

Answer 1

如果您的JDBC驱动程序支持它，请使用batch processing。它易于使用，并且在这种情况下往往效果很好。

Answer 2

有人可能有更好的想法，但您是否考虑过通过临时表将密钥列表传递给Oracle，然后在PL / SQL函数中执行循环。它会降低流量，DB会进行处理。

Answer 3

创建一个临时表并将所有ID插入其中。然后对临时表中的那些进行单个删除。

Answer 4

我认为最好使用CallableStatement和oracle procedure。

代码段

SQL> create type temp_tbl
  2  is
  3  table of number;
  4  /

...


SQL> create or replace procedure stored_p
  2  (
  3    list in temp_tbl,
  4    p_rc  out sys_refcursor )
  5  as
  6  begin
  7    open
  8   p_rc for delete from ACTIVESESSIONSLOG  where ASESSIONID
      in (select * from table(list));
  9  end;
 10  /

如何优化此SQL删除

4 个答案: