/** if some pages are too old, remove them */
public void removeOldPages() {
// the oldest page is in the front of the list, and the most recent page is in the tail of the
// list
int duration = curTime - pageStartTimes.get(0).start_time;
int count = 0;
// pay special attention to >=, if ==, still need to go ahead.
while (duration >= Configuration.T_period) {
count++;
if (count >= pageStartTimes.size()) break;
duration = curTime - pageStartTimes.get(count).start_time + 1;
}
// all previous data need to be erased.
for (int i = 0; i < count - 1; i++) {
m_pStorageManager.deleteByteArray(pageStartTimes.get(i).pageId);
}
// shifting, move all the data Item to the front of the list
for (int j = count - 1; j >= 0 && j < pageStartTimes.size(); j++) {
pageStartTimes.set(j - count + 1, pageStartTimes.get(j));
}
// erase the data at the tail after shifting
for (int i = 0; i < count - 1; i++) {
pageStartTimes.remove(pageStartTimes.size() - 1);
}
}
/**
* check the size of linkedhashmap, if the size of the map is larger that the flush threshold,
* flush all the items in linkedhashmap into disk
*
* <p>Think more about
* it........................!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
*/
private void flushBuffer() {
if (traHash.size() >= Configuration.CapacityPerPage) {
try {
byte[] data = BinarySerializer.getByteSerialize(traHash);
int id = m_pStorageManager.storeByteArray(IStorageManager.NewPage, data);
countIO++;
if (pageStartTimes.size() >= 1) {
removeOldPages(); // too old disk page are discarded
}
PageStartTimeItem pstItem = new PageStartTimeItem(curPageStartTime, id);
pageStartTimes.add(pstItem);
traHash.clear();
} catch (Exception e) {
e.printStackTrace();
}
}
}