/**
* Added to flush a particular page of the buffer pool to disk
*
* @param pageid the page number in the database.
* @exception HashOperationException if there is a hashtable error.
* @exception PageUnpinnedException if there is a page that is already unpinned.
* @exception PagePinnedException if a page is left pinned.
* @exception PageNotFoundException if a page is not found.
* @exception BufMgrException other error occured in bufmgr layer
* @exception IOException if there is other kinds of I/O error.
*/
public void flushPage(PageId pageId)
throws HashOperationException, PageUnpinnedException, PagePinnedException,
PageNotFoundException, BufMgrException, IOException {
BufMgrFrameDesc frame = pageTable.get(pageId);
if (frame != null) {
if (frame.isDirty()) {
try {
SystemDefs.JavabaseDB.write_page(pageId, new Page(frame.getData()));
} catch (Exception e) {
throw new BufMgrException(e, "BufrMgr::flushPage: page cant be freed by diskmanager");
}
}
frame.setDirtybit(false);
if (frame.getPinCount() > 0) {
throw new PagePinnedException(null, "BufrMgr::flushPage: page is still pinned");
}
} else {
throw new PageNotFoundException(null, "BufrMgr::flushPage: page to be flushed not loaded");
}
}
/**
* Gets the total number of unpinned buffer frames.
*
* @return total number of unpinned buffer frames.
*/
public int getNumUnpinnedBuffers() {
int unpinned = 0;
for (int i = 0; i < frameTable.length; i++) {
BufMgrFrameDesc frame = frameTable[i];
if (frame != null && frame.getPinCount() == 0) {
unpinned++;
} else if (frame == null) {
unpinned++;
}
}
return unpinned;
}
/**
* Check if this page is in buffer pool, otherwise find a frame for this page, read in and pin it.
* Also write out the old page if it's dirty before reading. If emptyPage==TRUE, then actually no
* read is done to bring the page in.
*
* @param pin_pgid page number in the minibase.
* @param page the pointer poit to the page.
* @param emptyPage true (empty page); false (non-empty page)
* @exception ReplacerException if there is a replacer error.
* @exception HashOperationException if there is a hashtable error.
* @exception PageUnpinnedException if there is a page that is already unpinned.
* @exception InvalidFrameNumberException if there is an invalid frame number .
* @exception PageNotReadException if a page cannot be read.
* @exception BufferPoolExceededException if the buffer pool is full.
* @exception PagePinnedException if a page is left pinned .
* @exception BufMgrException other error occured in bufmgr layer
* @exception IOException if there is other kinds of I/O error.
*/
public void pinPage(PageId pageId, Page page, boolean emptyPage)
throws ReplacerException, HashOperationException, PageUnpinnedException,
InvalidFrameNumberException, PageNotReadException, BufferPoolExceededException,
PagePinnedException, BufMgrException, IOException {
BufMgrFrameDesc frame = pageTable.get(pageId);
byte[] frameData;
if (frame != null) {
// page is already loaded
returnPageInfo(page, frame);
} else {
// page has to be loaded
// we need a victim frame
int victimFrameNo;
victimFrameNo = replacer.pick_victim();
BufMgrFrameDesc victimFrame = frameTable[victimFrameNo];
if (victimFrame != null && victimFrame.isDirty()) {
try {
flushPage(victimFrame.getPageNo());
} catch (PageNotFoundException e) {
throw new BufMgrException(e, "BufrMgr::pinPage: page number not found in flushPage");
}
}
frameData = buffer[victimFrameNo];
frameTable[victimFrameNo] = new BufMgrFrameDesc(pageId, frameData, victimFrameNo);
frame = frameTable[victimFrameNo];
// delete the entry from pageTable
if (victimFrame != null) {
pageTable.remove(victimFrame.getPageNo());
}
createPageTableEntry(pageId, page, emptyPage, frame);
}
}
/**
* User should call this method if s/he needs to delete a page. this routine will call DB to
* deallocate the page.
*
* @param globalPageId the page number in the data base.
* @exception InvalidBufferException if buffer pool corrupted.
* @exception ReplacerException if there is a replacer error.
* @exception HashOperationException if there is a hash table error.
* @exception InvalidFrameNumberException if there is an invalid frame number.
* @exception PageNotReadException if a page cannot be read.
* @exception BufferPoolExceededException if the buffer pool is already full.
* @exception PagePinnedException if a page is left pinned.
* @exception PageUnpinnedException if there is a page that is already unpinned.
* @exception HashEntryNotFoundException if there is no entry of page in the hash table.
* @exception IOException if there is other kinds of I/O error.
* @exception BufMgrException other error occured in bufmgr layer
* @exception DiskMgrException other error occured in diskmgr layer
*/
public void freePage(PageId pageId)
throws InvalidBufferException, ReplacerException, HashOperationException,
InvalidFrameNumberException, PageNotReadException, BufferPoolExceededException,
PagePinnedException, PageUnpinnedException, HashEntryNotFoundException, BufMgrException,
DiskMgrException, IOException {
BufMgrFrameDesc frame = pageTable.get(pageId);
if (frame != null) {
int pinCount = frame.getPinCount();
if (pinCount > 1) {
throw new PagePinnedException(null, "BufrMgr::freePage: page to be freed not loaded");
} else {
if (pinCount == 1) {
frame.unpin();
replacer.unpin(frame.getFrameNumber());
}
// remove from pagetable/frametable
pageTable.remove(pageId);
// add it to empty list
frameTable[frame.getFrameNumber()] = null;
replacer.free(frame.getFrameNumber());
// free it on disk
try {
SystemDefs.JavabaseDB.deallocate_page(pageId);
} catch (Exception e1) {
throw new DiskMgrException(
e1, "BUFMGR::freepage failed " + "after pinPage failed and deallocate page failed");
}
}
} else {
// free it on disk
try {
SystemDefs.JavabaseDB.deallocate_page(pageId);
} catch (Exception e1) {
throw new DiskMgrException(e1, "BUFMGR::freepage failed");
}
}
}
/**
* To unpin a page specified by a pageId. If pincount>0, decrement it and if it becomes zero, put
* it in a group of replacement candidates. if pincount=0 before this call, return error.
*
* @param globalPageId_in_a_DB page number in the minibase.
* @param dirty the dirty bit of the frame
* @exception ReplacerException if there is a replacer error.
* @exception PageUnpinnedException if there is a page that is already unpinned.
* @exception InvalidFrameNumberException if there is an invalid frame number .
* @exception HashEntryNotFoundException if there is no entry of page in the hash table.
*/
public void unpinPage(PageId pageId, boolean dirty)
throws ReplacerException, PageUnpinnedException, HashEntryNotFoundException,
InvalidFrameNumberException {
BufMgrFrameDesc frame = pageTable.get(pageId);
if (frame != null) {
int pinCount = frame.getPinCount();
if (pinCount == 0) {
throw new PageUnpinnedException(
null, "BufrMgr::unPinPage: page to be unpinned is already unpinned");
} else {
frame.unpin();
if (frame.getPinCount() == 0) replacer.unpin(frame.getFrameNumber());
}
frame.setDirtybit(dirty);
} else {
throw new HashEntryNotFoundException(
null, "BufrMgr::unPinPage: page to be unpinned not loaded");
}
}
private void returnPageInfo(Page page, BufMgrFrameDesc frame) throws InvalidFrameNumberException {
frame.pin();
replacer.pin(frame.getFrameNumber());
page.setpage(frame.getData());
}
