为所有列实施搜索过滤器

Question

我在PostgreSQL http://www.postgresql.org/docs/current/interactive/textsearch-tables.html#TEXTSEARCH-TABLES-SEARCH

中找到了这个搜索示例

我尝试以这种方式为此表实现此代码：

CREATE TABLE ACCOUNT(
 ID INTEGER NOT NULL,
 USER_NAME TEXT,
 PASSWD TEXT,
 FIRST_NAME TEXT,
 LAST_NAME TEXT,
 LAST_LOGIN DATE,
 DATE_REGISTERED DATE,
 ROLE INTEGER,
 CAN_LOGIN INTEGER
)
;

-- ADD KEYS FOR TABLE ACCOUNT

ALTER TABLE ACCOUNT ADD CONSTRAINT KEY1 PRIMARY KEY (ID)
;

Java代码

public List<AccountsObj> list(int firstRow, int rowCount, String sortField, boolean sortAscending) throws SQLException
    {
        String SqlStatement = null;

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

        String sortDirection = sortAscending ? "ASC" : "DESC";

        SqlStatement = "SELECT * FROM ACCOUNT "
//            + " WHERE ? IS NULL OR ? IN (USER_NAME, FIRST_NAME, LAST_NAME)"
            + " WHERE to_tsvector('english', USER_NAME || ' ' ) @@ plainto_tsquery(?)"
            + " ORDER BY %S %S offset ? limit ? ";

        String sql = String.format(SqlStatement, sortField, sortDirection);

        PreparedStatement ps = null;
        ResultSet resultSet = null;
        List<AccountsObj> resultList = new ArrayList<>();

        try
        {
            conn.setAutoCommit(false);
            boolean committed = false;

            ps = conn.prepareStatement(sql);

            ps.setString(1, searchString);
            ps.setInt(2, firstRow);
            ps.setInt(3, rowCount);

            resultSet = ps.executeQuery();
            resultList = ProcessorArrayList(resultSet);

            conn.commit();
            committed = true;

        }
        finally
        {
            ps.close();
            conn.close();
        }

        return resultList;
    }

但我有两个问题。当搜索字符串为空时，表也为空。我怎么能解决这个问题？我还可以如何为每个表格列实现此搜索？

P.S我试过WHERE to_tsvector('english', USER_NAME || ' ' ) @@ plainto_tsquery(?) IS NOT NULL

但未应用搜索过滤器。