stasis-aries-wal/lladd/bufferManager.h

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---*/
/**
 * @file
 * Manages the page buffer

    pageManager - Provides cached page handling, delegates to blob
    manager when necessary.  Doesn't implement an eviction policy.
    That is left to a cacheManager.  (Multiple cacheManagers could be
    used with a single page manager.)

  @todo Allow error checking!  
 
  @todo Refactoring for lock manager
 
  Possible interface for lockManager:

       Define three classes of objects that the lock manager is interested in:

         Transactions,
	 Operations,
	 Predicates.

       LLADD already has operations and transactions, and these can be
       relatively unchanged.  Predicates are read only operations that
       return a set of tuples.  Tread() is the simplest predicate.
       Index scans provide a motivating example.  

       See http://research.microsoft.com/%7Eadya/pubs/icde00.pdf
       (Generalized Isolation Level Definitions, Adya, Liskov, O'Neil,
       2000) for a theoretical discussion of general locking schemes..

       Locking functions can return errors such as DEADLOCK, etc.
       When such a value is returned, the transaction aborts, and an
       error is passed up to the application.

 * @ingroup LLADD_CORE
 * $Id$
 */

#include <lladd/constants.h>
#include <lladd/transactional.h>

#ifndef __BUFFERMANAGER_H__
#define __BUFFERMANAGER_H__

BEGIN_C_DECLS

/**
   Page is defined in bufferManager.h as an incomplete type to enforce
   an abstraction barrier between page.h and the rest of the system.

   If you need to muck with page internals, first consider the
   implications that doing so has on locking.  In particular, rwlatch
   is currently entirely handled in page.c.
*/
typedef struct Page_s Page_s;
typedef struct Page_s Page;

/**
 * @param xid The transaction that is pinning the page (used by page-level locking implementations.)
 * @param pageid ID of the page you want to load
 * @return fully formed Page type
 */
compensated_function Page * loadPage(int xid, int pageid);

/**
   loadPage aquires a lock when it is called, effectively pinning it
   in memory.  releasePage releases this lock.
*/
void releasePage(Page * p);

//#define loadPage(xid, pageid) loadPage(xid, pageid); printf("%s %d: thread=%d loadPage(%d, %d)\n", __FILE__, __LINE__, pthread_self(), (xid), (pageid));
//#define releasePage(pageid) releasePage(pageid); printf("%s,%d: thread=%d releasePage()\n", __FILE__, __LINE__, pthread_self()); 

#ifdef PROFILE_LATCHES_WRITE_ONLY
#define loadPage(x,y) __profile_loadPage((x), (y), __FILE__, __LINE__)
#define releasePage(x) __profile_releasePage((x))
compensated_function void  __profile_releasePage(Page * p);
compensated_function Page * __profile_loadPage(int xid, int pageid, char * file, int line);
#endif


/**
 * initialize buffer manager
 * @return 0 on success
 * @return error code on failure
 */
int bufInit();

/**
 * will write out any dirty pages, assumes that there are no running
 * transactions
 */
void bufDeinit();

END_C_DECLS

#endif