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Copy pathBufferPool.java
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312 lines (272 loc) · 8.74 KB
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package simpledb;
import java.io.*;
import java.util.ArrayList;
import java.util.Set;
//import java.util.ArrayList;
import java.util.concurrent.ConcurrentHashMap;
/**
* BufferPool manages the reading and writing of pages into memory from
* disk. Access methods call into it to retrieve pages, and it fetches
* pages from the appropriate location.
* <p>
* The BufferPool is also responsible for locking; when a transaction fetches
* a page, BufferPool checks that the transaction has the appropriate
* locks to read/write the page.
*
* @Threadsafe, all fields are final
*/
public class BufferPool {
/** Bytes per page, including header. */
private static final int PAGE_SIZE = 4096;
//private static final int PAGE_SIZE = 4;
private static int pageSize = PAGE_SIZE;
private ConcurrentHashMap<PageId, Page> pages;
private int maxPages;
/** Default number of pages passed to the constructor. This is used by
other classes. BufferPool should use the numPages argument to the
constructor instead. */
public static final int DEFAULT_PAGES = 50;
/**
* Creates a BufferPool that caches up to numPages pages.
*
* @param numPages maximum number of pages in this buffer pool.
*/
public BufferPool(int numPages) {
// some code goes here
//pageSize = numPages; //wrong
pages = new ConcurrentHashMap<PageId, Page>(numPages);
maxPages = numPages;
}
public static int getPageSize() {
return pageSize;
}
// THIS FUNCTION SHOULD ONLY BE USED FOR TESTING!!
public static void setPageSize(int pageSize) {
BufferPool.pageSize = pageSize;
}
// THIS FUNCTION SHOULD ONLY BE USED FOR TESTING!!
public static void resetPageSize() {
BufferPool.pageSize = PAGE_SIZE;
}
/**
* Retrieve the specified page with the associated permissions.
* Will acquire a lock and may block if that lock is held by another
* transaction.
* <p>
* The retrieved page should be looked up in the buffer pool. If it
* is present, it should be returned. If it is not present, it should
* be added to the buffer pool and returned. If there is insufficient
* space in the buffer pool, an page should be evicted and the new page
* should be added in its place.
*
* @param tid the ID of the transaction requesting the page
* @param pid the ID of the requested page
* @param perm the requested permissions on the page
*/
public Page getPage(TransactionId tid, PageId pid, Permissions perm)
throws TransactionAbortedException, DbException {
// some code goes here
//System.out.println("BufferPool getPage()");
Page output;
//int key = pid.hashCode();
if(pages.containsKey(pid))
{
//System.out.println("found pageID in bufferPool");
output = pages.get(pid);
}
else
{
if(pages.size()>= maxPages)
{
try {
evictPage();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
//System.out.println("didn't find pageID in bufferPool");
Catalog current_catalog = Database.getCatalog();
int tableid = pid.getTableId();
DbFile current_dbf = current_catalog.getDatabaseFile(tableid);
Page to_add = current_dbf.readPage(pid);
//System.out.println("Pages - before: " + pages);
output = pages.put(pid, to_add);
//System.out.println("Pages - after: " + pages);
//System.out.println("Output page: " + output);
output = to_add;
}
return output;
}
/**
* Releases the lock on a page.
* Calling this is very risky, and may result in wrong behavior. Think hard
* about who needs to call this and why, and why they can run the risk of
* calling it.
*
* @param tid the ID of the transaction requesting the unlock
* @param pid the ID of the page to unlock
*/
public void releasePage(TransactionId tid, PageId pid) {
// some code goes here
// not necessary for lab1|lab2
}
/**
* Release all locks associated with a given transaction.
*
* @param tid the ID of the transaction requesting the unlock
*/
public void transactionComplete(TransactionId tid) throws IOException {
// some code goes here
// not necessary for lab1|lab2
}
/** Return true if the specified transaction has a lock on the specified page */
public boolean holdsLock(TransactionId tid, PageId p) {
// some code goes here
// not necessary for lab1|lab2
return false;
}
/**
* Commit or abort a given transaction; release all locks associated to
* the transaction.
*
* @param tid the ID of the transaction requesting the unlock
* @param commit a flag indicating whether we should commit or abort
*/
public void transactionComplete(TransactionId tid, boolean commit)
throws IOException {
// some code goes here
// not necessary for lab1|lab2
}
/**
* Add a tuple to the specified table on behalf of transaction tid. Will
* acquire a write lock on the page the tuple is added to and any other
* pages that are updated (Lock acquisition is not needed for lab2).
* May block if the lock(s) cannot be acquired.
*
* Marks any pages that were dirtied by the operation as dirty by calling
* their markDirty bit, and adds versions of any pages that have
* been dirtied to the cache (replacing any existing versions of those pages) so
* that future requests see up-to-date pages.
*
* @param tid the transaction adding the tuple
* @param tableId the table to add the tuple to
* @param t the tuple to add
*/
public void insertTuple(TransactionId tid, int tableId, Tuple t)
throws DbException, IOException, TransactionAbortedException {
// some code goes here
// not necessary for lab1
DbFile table_needed = Database.getCatalog().getDatabaseFile(tableId);
ArrayList<Page> updated = table_needed.insertTuple(tid, t);
for(Page p : updated)
{
p.markDirty(true, tid);
pages.put(p.getId(), p);
}
}
/**
* Remove the specified tuple from the buffer pool.
* Will acquire a write lock on the page the tuple is removed from and any
* other pages that are updated. May block if the lock(s) cannot be acquired.
*
* Marks any pages that were dirtied by the operation as dirty by calling
* their markDirty bit, and adds versions of any pages that have
* been dirtied to the cache (replacing any existing versions of those pages) so
* that future requests see up-to-date pages.
*
* @param tid the transaction deleting the tuple.
* @param t the tuple to delete
*/
public void deleteTuple(TransactionId tid, Tuple t)
throws DbException, IOException, TransactionAbortedException {
// some code goes here
// not necessary for lab1
HeapPage hp = ((HeapPage) getPage(tid, t.getRecordId().getPageId(), Permissions.READ_WRITE));
hp.deleteTuple(t);
hp.markDirty(true, tid);
pages.put(hp.getId(), hp);
}
/**
* Flush all dirty pages to disk.
* NB: Be careful using this routine -- it writes dirty data to disk so will
* break simpledb if running in NO STEAL mode.
*/
public synchronized void flushAllPages() throws IOException {
// some code goes here
// not necessary for lab1
Set<PageId> bP_Keyset = pages.keySet();
for(PageId pid : bP_Keyset)
{
flushPage(pid);
}
}
/** Remove the specific page id from the buffer pool.
Needed by the recovery manager to ensure that the
buffer pool doesn't keep a rolled back page in its
cache.
Also used by B+ tree files to ensure that deleted pages
are removed from the cache so they can be reused safely
*/
public synchronized void discardPage(PageId pid) {
// some code goes here
// not necessary for lab1
pages.remove(pid);
}
/**
* Flushes a certain page to disk
* @param pid an ID indicating the page to flush
*/
private synchronized void flushPage(PageId pid) throws IOException {
// some code goes here
// not necessary for lab1
try
{
Page p = pages.remove(pid);
int tableid = pid.getTableId();
HeapFile hf = (HeapFile) Database.getCatalog().getDatabaseFile(tableid);
hf.writePage(p);
}
catch(IOException e)
{
e.printStackTrace();
}
}
/** Write all pages of the specified transaction to disk.
*/
public synchronized void flushPages(TransactionId tid) throws IOException {
// some code goes here
// not necessary for lab1|lab2
}
/**
* Discards a page from the buffer pool.
* Flushes the page to disk to ensure dirty pages are updated on disk.
* @throws IOException
*/
private synchronized void evictPage() throws DbException, IOException {
// some code goes here
// not necessary for lab1
boolean foundPage = false;
Set<PageId> bP_Keyset = pages.keySet();
for(PageId pid : bP_Keyset)
{
Page p = pages.get(pid);
//page clean
if(p.isDirty() == null)
{
discardPage(pid);
foundPage = true;
break;
}
}
if(!foundPage)
{
for(PageId pid : bP_Keyset)
{
flushPage(pid);
foundPage = true;
break;
}
}
}
}
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