stasis-aries-wal/lladd/operations.h

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/**
 * @file
 *
 * Interface for defining new logical operations.
 *
 * @ingroup LLADD_CORE OPERATIONS
 * @todo The functions in operations.h don't belong in the API, but it defines some constants and typedefs that should be there.
 * $Id$
 */

#ifndef __OPERATIONS_H__
#define __OPERATIONS_H__

#include <lladd/constants.h>
#include <lladd/transactional.h>
#include <lladd/logger/logEntry.h> 
#include <lladd/bufferManager.h>

BEGIN_C_DECLS


/** 
 * function pointer that the operation will run
 */
typedef int (*Function)(int xid, Page * p, lsn_t lsn, recordid r, const void *d);

/**

*/

/**
   If the Operation struct's sizeofData is set to this value, then the
   size field of the recordid is used to determine the size of the
   argument passed into the operation.
 */
#define SIZEOF_RECORD -1
/** If the Operation struct's undo field is set to this value, then
    physical logging is used in lieu of logical logging.
 */

#define NO_INVERSE -1
typedef struct {
  /**
   * ID of operation, also index into operations table
   */
	int id;
  /** 
      This value is the size of the arguments that this operation
      takes.  If set to SIZEOF_RECORD, then the size of the record
      that the operation affects will be used instead.
  */
	long sizeofData;
  /**
     Implementing operations that may span records is subtle.
     Recovery assumes that page writes (and therefore logical
     operations) are atomic.  This isn't the case for operations that
     span records.  Instead, there are two (and probably other) choices:

      - Periodically checkpoint, syncing the data store to disk, and
        writing a checkpoint operation.  No writes can be serviced
        during the sync, and this implies 'no steal'.  See: 

        @inproceedings{ woo97accommodating,
	author = "Seung-Kyoon Woo and Myoung-Ho Kim and Yoon-Joon Lee",
	title = "Accommodating Logical Logging under Fuzzy Checkpointing in Main Memory Databases",
	booktitle = "International Database Engineering and Application Symposium",
	pages = "53-62",
	year = "1997",
	url = "citeseer.ist.psu.edu/135200.html" }

	for a more complex scheme involving a hybrid logical/physical
	logging system that does not implement steal.

	The other option: 

      - Get rid of operations that span records entirely by
        splitting complex logical operations into simpler ones.

	We chose the second option for now.  This implies that the
	entries must be written to the log in an order, that if
	repeated, guarantees that the structure will be in a logically
	consistent state after the REDO phase, regardless of what
	prefix of the log actually makes it to disk.  Note that
	pinning pages before the log entry hits disk is inadequate, in
	general, since other transactions could read dirty information
	from the pinned pages, producsing nonsensical log entries that
	preceed the current transaction's log entry.
	
   */
  /**
     index into operations table of undo function
  */
  int undo;
  Function run;
} Operation;

/* These need to be installed, since they are required by applications that use LLADD. */

#include "operations/increment.h"
#include "operations/decrement.h"
#include "operations/set.h"
#include "operations/prepare.h"
#include "operations/lladdhash.h"
#include "operations/alloc.h"
#include "operations/pageOperations.h"
#include "operations/noop.h"
#include "operations/instantSet.h"
#include "operations/arrayList.h"
#include "operations/linearHash.h"
#include "operations/naiveLinearHash.h"
extern Operation operationsTable[]; /* [MAX_OPERATIONS];  memset somewhere */

/** Performs an operation during normal execution. 

    Does not write to the log, and assumes that the operation's
    results are not already in the buffer manager.
*/
void doUpdate(const LogEntry * e, Page * p);
/** Undo the update under normal operation, and during recovery. 

    Checks to see if the operation's results are reflected in the
    contents of the buffer manager.  If they are, then it performs the
    undo.  

    Does not write to the log.

    This function does not generate CLR because this would result in
    extra CLRs being generated during recovery.

    @param e The log entry containing the operation to be undone.  
    @param p A pointer to the memory resident copy of the page that is being managed by bufferManager.
    @param clr_lsn The lsn of the clr that corresponds to this undo operation.
*/
void undoUpdate(const LogEntry * e, Page * p, lsn_t clr_lsn);
/** 
    Redoes an operation during recovery.  This is different than
    doUpdate because it checks to see if the operation needs to be redone
    before redoing it. (if(e->lsn > e->rid.lsn) { doUpdate(e); } return)

    Also, this is the only function in operations.h that can take
    either CLR or UPDATE log entries.  The other functions can     handle update entries.

    Does not write to the log.
*/
void redoUpdate(const LogEntry * e);

END_C_DECLS

#endif