wiscdb::BufferManager 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
	BufferManager (std::uint32_t bufs)
	~BufferManager ()
void	readPage (File *file, const PageId PageNo, Page *&page)
void	unPinPage (File *file, const PageId PageNo, const bool dirty)
void	allocatePage (File *file, PageId &PageNo, Page *&page)
void	flushFile (const File *file)
void	disposePage (File *file, const PageId PageNo)
void	printSelf ()
BufferStats &	getBufferStats ()
void	clearBufferStats ()

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 131 of file buffer.h.

Constructor & Destructor Documentation

wiscdb::BufferManager::BufferManager

(

std::uint32_t

bufs

)

Constructor of BufferManager class

wiscdb::BufferManager::~BufferManager

(

)

Destructor of BufferManager class

Member Function Documentation

void wiscdb::BufferManager::allocatePage	(	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.

void wiscdb::BufferManager::clearBufferStats ( )

inline

Clear buffer pool usage statistics

Definition at line 271 of file buffer.h.

  {
    bufferStats.clear();
  }

void wiscdb::BufferManager::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

void wiscdb::BufferManager::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 an exception is thrown.

Parameters

file	File object to flush to disk

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

BufferStats& wiscdb::BufferManager::getBufferStats ( )

inline

Get buffer pool usage statistics

Definition at line 263 of file buffer.h.

  {
    return bufferStats;
  }

void wiscdb::BufferManager::printSelf

(

)

Print member variable values.

void wiscdb::BufferManager::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, its pin count is increased and a 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.

void wiscdb::BufferManager::unPinPage	(	File *	file,
		const PageId	PageNo,
		const bool	dirty
	)

Unpin a page from memory when one requesting application no longer requires 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

Member Data Documentation

Page* wiscdb::BufferManager::bufPool

Actual buffer pool of Pages. A table of Page objects, with each index corresponding to Frame at the same index of frameTable.

Definition at line 182 of file buffer.h.

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

• buffer.h