SQLite

** The pager is used to access a database disk file.  It implements
** atomic commit and rollback through the use of a journal file that
** is separate from the database file.  The pager also implements file
** locking to prevent two processes from writing the same database
** file simultaneously, or one process from reading the database while
** another is writing.
**
** @(#) $Id: pager.c,v 1.545 2009/01/10 16:15:09 danielk1977 Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"

/*
** Macros for troubleshooting.  Normally turned off
*/

    }

    /* If the PGHDR_NEED_SYNC flag is set for any of the nPage pages 
    ** starting at pg1, then it needs to be set for all of them. Because
    ** writing to any of these nPage pages may damage the others, the
    ** journal file must contain sync()ed copies of all of them
    ** before any of them can be written out to the database file.
    **
    ** 2009-01-07:  This block of code appears to be a no-op.  I do not
    ** believe it is possible for any page on the sector to not have
    ** the PGHDR_NEED_SYNC flag set.  The "pPage->flags |= PGHDR_NEED_SYNC"
    ** line below does nothing, I think.  But it does no harm to leave
    ** this code in place until we can definitively prove this is the case.
    */
    if( needSync ){
      assert( !MEMDB && pPager->noSync==0 );
      for(ii=0; ii<nPage && needSync; ii++){
        PgHdr *pPage = pager_lookup(pPager, pg1+ii);
        if( pPage ){
          assert( pPage->flags & PGHDR_NEED_SYNC ); /* 2009-01-07 conjecture */
          pPage->flags |= PGHDR_NEED_SYNC;
          sqlite3PagerUnref(pPage);
        }
      }
      assert(pPager->needSync);
    }