badgerdb::BufMgr Class Reference

The central class which manages the buffer pool including frame allocation and deallocation to pages in the file. More...

#include <buffer.h>

Public Member Functions
	BufMgr (std::uint32_t bufs)
	~BufMgr ()
void	readPage (File *file, const PageId PageNo, Page *&page)
void	unPinPage (File *file, const PageId PageNo, const bool dirty)
void	allocPage (File *file, PageId &PageNo, Page *&page)
void	flushFile (const File *file)
void	disposePage (File *file, const PageId PageNo)
void	printSelf ()
BufStats &	getBufStats ()
void	clearBufStats ()

Public Attributes
Page *	bufPool

Detailed Description

The central class which manages the buffer pool including frame allocation and deallocation to pages in the file.

Definition at line 160 of file buffer.h.

Constructor & Destructor Documentation

badgerdb::BufMgr::BufMgr

(

std::uint32_t

bufs

)

Constructor of BufMgr class

Definition at line 19 of file buffer.cpp.

  : numBufs(bufs) {
  bufDescTable = new BufDesc[bufs];

  for (FrameId i = 0; i < bufs; i++) 
  {
    bufDescTable[i].frameNo = i;
    bufDescTable[i].valid = false;
  }

  bufPool = new Page[bufs];

  int htsize = ((((int) (bufs * 1.2))*2)/2)+1;
  hashTable = new BufHashTbl (htsize);  // allocate the buffer hash table

  clockHand = bufs - 1;
}

badgerdb::BufMgr::~BufMgr

(

)

Destructor of BufMgr class

Definition at line 38 of file buffer.cpp.

                {

  // 1. Flush all dirty pages to disk
  for ( std::uint32_t i = 0 ; i < numBufs; ++i ) {
    if (bufDescTable[i].dirty) {
      bufDescTable[i].file->writePage(bufPool[i]);
    }
  }
  // 2. deallocate buffer pool
  delete hashTable; // ?? not mentioned in the pdf
  delete [] bufPool;
  // 3. deallocate BufDesc table
  delete [] bufDescTable;


}

Member Function Documentation

void badgerdb::BufMgr::allocPage	(	File *	file,
		PageId &	PageNo,
		Page *&	page
	)

Allocates a new, empty page in the file and returns the Page object. The newly allocated page is also assigned a frame in the buffer pool.

Parameters

file	File object
PageNo	Page number. The number assigned to the page in the file is returned via this reference.
page	Reference to page pointer. The newly allocated in-memory Page object is returned via this reference.

Definition at line 177 of file buffer.cpp.

{
  FrameId frameNo;
  allocBuf(frameNo);
  bufPool[frameNo] = file->allocatePage();
  pageNo = bufPool[frameNo].page_number();
// fprintf(stderr, "info: %s +%d %s\n", __FILE__, __LINE__, __func__);

  hashTable->insert(file, pageNo, frameNo);
  bufDescTable[frameNo].Set(file, pageNo);
  page = &bufPool[frameNo];
}

void badgerdb::BufMgr::clearBufStats ( )

inline

Clear buffer pool usage statistics

Definition at line 284 of file buffer.h.

  {
    bufStats.clear();
  }

void badgerdb::BufMgr::disposePage	(	File *	file,
		const PageId	PageNo
	)

Delete page from file and also from buffer pool if present. Since the page is entirely deleted from file, its unnecessary to see if the page is dirty.

Parameters

file	File object
PageNo	Page number

Definition at line 191 of file buffer.cpp.

{
  FrameId frameNo;
  if ( hashTable->lookup(file, PageNo, frameNo) ) {
    BufDesc* tmpbuf = &bufDescTable[frameNo];
    hashTable->remove(tmpbuf->file, tmpbuf->pageNo);
    tmpbuf->Clear();
  }
  file->deletePage(PageNo);

}

void badgerdb::BufMgr::flushFile

(

const File *

file

)

Writes out all dirty pages of the file to disk. All the frames assigned to the file need to be unpinned from buffer pool before this function can be successfully called. Otherwise Error returned.

Parameters

file	File object

Exceptions

PagePinnedException	If any page of the file is pinned in the buffer pool
BadBufferException	If any frame allocated to the file is found to be invalid

Definition at line 148 of file buffer.cpp.

{

  BufDesc* tmpbuf;
  for (std::uint32_t i = 0 ; i < numBufs ; ++i ) {
    tmpbuf = &bufDescTable[i];
    if ( tmpbuf->file == file ) { //Is this the way to check if belong to same file?
      if ( tmpbuf->pinCnt > 0 )  {
        throw PagePinnedException(file->filename(), 
                                tmpbuf->pageNo,
                                tmpbuf->frameNo);
      }
      if ( ! tmpbuf->valid ) {
          throw BadBufferException(tmpbuf->frameNo,
                                   tmpbuf->dirty,
                                   tmpbuf->valid,
                                   tmpbuf->refbit);
      }
      if ( tmpbuf->dirty )
        tmpbuf->file->writePage(bufPool[i]);
      hashTable->remove(tmpbuf->file, tmpbuf->pageNo);
      tmpbuf->Clear();

    }
  }

}

BufStats& badgerdb::BufMgr::getBufStats ( )

inline

Get buffer pool usage statistics

Definition at line 276 of file buffer.h.

  {
    return bufStats;
  }

void badgerdb::BufMgr::printSelf

(

void

)

Print member variable values.

Definition at line 204 of file buffer.cpp.

{
  BufDesc* tmpbuf;
  int validFrames = 0;
  
  for (std::uint32_t i = 0; i < numBufs; i++)
  {
        tmpbuf = &(bufDescTable[i]);
    std::cout << "FrameNo:" << i << " ";
    tmpbuf->Print();

    if (tmpbuf->valid == true)
      validFrames++;
  }

  std::cout << "Total Number of Valid Frames:" << validFrames << "\n";
}

void badgerdb::BufMgr::readPage	(	File *	file,
		const PageId	PageNo,
		Page *&	page
	)

Reads the given page from the file into a frame and returns the pointer to page. If the requested page is already present in the buffer pool pointer to that frame is returned otherwise a new frame is allocated from the buffer pool for reading the page.

Parameters

file	File object
PageNo	Page number in the file to be read
page	Reference to page pointer. Used to fetch the Page object in which requested page from file is read in.

Definition at line 117 of file buffer.cpp.

{
  FrameId frameNo;
  if ( hashTable->lookup(file, pageNo, frameNo) ) { // found
    bufDescTable[frameNo].refbit = true;
    bufDescTable[frameNo].pinCnt++;
  } else { // not found
    allocBuf(frameNo);
    bufPool[frameNo] = file->readPage(pageNo);
    hashTable->insert(file, pageNo, frameNo);
    bufDescTable[frameNo].Set(file, pageNo);
  }
  page = &bufPool[frameNo];
}

void badgerdb::BufMgr::unPinPage	(	File *	file,
		const PageId	PageNo,
		const bool	dirty
	)

Unpin a page from memory since it is no longer required for it to remain in memory.

Parameters

file	File object
PageNo	Page number
dirty	True if the page to be unpinned needs to be marked dirty

Exceptions

PageNotPinnedException

If the page is not already pinned

Definition at line 133 of file buffer.cpp.

{
  FrameId frameNo;
  if ( hashTable->lookup(file, pageNo, frameNo)) { // found
    if ( dirty ) bufDescTable[frameNo].dirty = true;
    if ( bufDescTable[frameNo].pinCnt > 0 ) {
      bufDescTable[frameNo].pinCnt--;
    } else {
      throw PageNotPinnedException(file->filename(), pageNo, frameNo);
    }
  }

}

Member Data Documentation

Page* badgerdb::BufMgr::bufPool

Actual buffer pool from which frames are allocated

Definition at line 205 of file buffer.h.

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The documentation for this class was generated from the following files:

• /afs/cs.wisc.edu/u/h/a/haiyun/private/cs564-spr17/projects/p2/BufMgr/src/buffer.h
• /afs/cs.wisc.edu/u/h/a/haiyun/private/cs564-spr17/projects/p2/BufMgr/src/buffer.cpp