Hibernate分页查询原理解读

Query q = session.createQuery("from Cat as c");
　　q.setFirstResult(20000);
　　q.setMaxResults(100);
　　List l = q.list();   

if (useLimit) sql = dialect.getLimitString(sql);
　　PreparedStatement st = session.getBatcher().prepareQueryStatement(sql, scrollable);   

　public boolean supportsLimit() ...{
　　return true;
　　}
　　public String getLimitString(String sql) ...{
　　StringBuffer pagingSelect = new StringBuffer(100);
　　pagingSelect.append(sql);
　　pagingSelect.append(" limit ?, ?");
　　return pagingSelect.toString();
　　}   

public boolean supportsLimit() ...{
　　return true;
　　}

　　public String getLimitString(String sql) ...{
　　StringBuffer pagingSelect = new StringBuffer(100);
　　pagingSelect.append("select * from ( select row_.*, rownum rownum_ from ( ");
　　pagingSelect.append(sql);
　　pagingSelect.append(" ) row_ where rownum <= ?) where rownum_ > ?");
　　return pagingSelect.toString();
　　}   

if ( session.getFactory().useScrollableResultSets() ) ...{
　　// we can go straight to the first required row    
　　rs.absolute(firstRow);
　　}
　　else ...{
　　// we need to step through the rows one row at a time (slow)    
　　for ( int m=0; m　　}