SQLite

/*
** 2004 April 6
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** $Id: btree.c,v 1.589 2009/04/02 20:16:59 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
** Including a description of file format and an overview of operation.
*/
#include "btreeInt.h"

  sqlite3BtreeLeave(p);
  return rc;
}

#if !defined(SQLITE_OMIT_PAGER_PRAGMAS) || !defined(SQLITE_OMIT_VACUUM)
/*
** Change the default pages size and the number of reserved bytes per page.
** Or, if the page size has already been fixed, return SQLITE_READONLY 
** without changing anything.
**
** The page size must be a power of 2 between 512 and 65536.  If the page
** size supplied does not meet this constraint then the page size is not
** changed.
**
** Page sizes are constrained to be a power of two so that the region
** of the database file used for locking (beginning at PENDING_BYTE,
** the first byte past the 1GB boundary, 0x40000000) needs to occur
** at the beginning of a page.
**
** If parameter nReserve is less than zero, then the number of reserved
** bytes per page is left unchanged.
**
** If the iFix!=0 then the pageSizeFixed flag is set so that the page size
** and autovacuum mode can no longer be changed.
*/
int sqlite3BtreeSetPageSize(Btree *p, int pageSize, int nReserve, int iFix){
  int rc = SQLITE_OK;
  BtShared *pBt = p->pBt;
  assert( nReserve>=-1 && nReserve<=255 );
  sqlite3BtreeEnter(p);
  if( pBt->pageSizeFixed ){
    sqlite3BtreeLeave(p);
    return SQLITE_READONLY;

    assert( (pageSize & 7)==0 );
    assert( !pBt->pPage1 && !pBt->pCursor );
    pBt->pageSize = (u16)pageSize;
    freeTempSpace(pBt);
    rc = sqlite3PagerSetPagesize(pBt->pPager, &pBt->pageSize);
  }
  pBt->usableSize = pBt->pageSize - (u16)nReserve;
  if( iFix ) pBt->pageSizeFixed = 1;
  sqlite3BtreeLeave(p);
  return rc;
}

/*
** Return the currently defined page size
*/

**    May you share freely, never taking more than you give.
**
*************************************************************************
** This header file defines the interface that the sqlite B-Tree file
** subsystem.  See comments in the source code for a detailed description
** of what each interface routine does.
**
** @(#) $Id: btree.h,v 1.112 2009/04/02 20:16:59 drh Exp $
*/
#ifndef _BTREE_H_
#define _BTREE_H_

/* TODO: This definition is just included so other modules compile. It
** needs to be revisited.
*/

#define BTREE_READWRITE    16  /* Open for both reading and writing */
#define BTREE_CREATE       32  /* Create the database if it does not exist */

int sqlite3BtreeClose(Btree*);
int sqlite3BtreeSetCacheSize(Btree*,int);
int sqlite3BtreeSetSafetyLevel(Btree*,int,int);
int sqlite3BtreeSyncDisabled(Btree*);
int sqlite3BtreeSetPageSize(Btree*,int,int,int);
int sqlite3BtreeGetPageSize(Btree*);
int sqlite3BtreeMaxPageCount(Btree*,int);
int sqlite3BtreeGetReserve(Btree*);
int sqlite3BtreeSetAutoVacuum(Btree *, int);
int sqlite3BtreeGetAutoVacuum(Btree *);
int sqlite3BtreeBeginTrans(Btree*,int);
int sqlite3BtreeCommitPhaseOne(Btree*, const char *zMaster);

/*
** 2003 April 6
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains code used to implement the PRAGMA command.
**
** $Id: pragma.c,v 1.205 2009/04/02 20:16:59 drh Exp $
*/
#include "sqliteInt.h"

/* Ignore this whole file if pragmas are disabled
*/
#if !defined(SQLITE_OMIT_PRAGMA) && !defined(SQLITE_OMIT_PARSER)

      int size = ALWAYS(pBt) ? sqlite3BtreeGetPageSize(pBt) : 0;
      returnSingleInt(pParse, "page_size", size);
    }else{
      /* Malloc may fail when setting the page-size, as there is an internal
      ** buffer that the pager module resizes using sqlite3_realloc().
      */
      db->nextPagesize = atoi(zRight);
      if( SQLITE_NOMEM==sqlite3BtreeSetPageSize(pBt, db->nextPagesize, -1, 0) ){
        db->mallocFailed = 1;
      }
    }
  }else

  /*
  **  PRAGMA [database.]max_page_count

**
*************************************************************************
** This file contains code used to implement the VACUUM command.
**
** Most of the code in this file may be omitted by defining the
** SQLITE_OMIT_VACUUM macro.
**
** $Id: vacuum.c,v 1.87 2009/04/02 20:16:59 drh Exp $
*/
#include "sqliteInt.h"
#include "vdbeInt.h"

#if !defined(SQLITE_OMIT_VACUUM) && !defined(SQLITE_OMIT_ATTACH)
/*
** Execute zSql on database db. Return an error code.

    int nKey;
    char *zKey;
    sqlite3CodecGetKey(db, 0, (void**)&zKey, &nKey);
    if( nKey ) db->nextPagesize = 0;
  }
#endif

  if( sqlite3BtreeSetPageSize(pTemp, sqlite3BtreeGetPageSize(pMain), nRes, 0)
   || (!isMemDb && sqlite3BtreeSetPageSize(pTemp, db->nextPagesize, nRes, 0))
   || db->mallocFailed 
  ){
    rc = SQLITE_NOMEM;
    goto end_of_vacuum;
  }
  rc = execSql(db, "PRAGMA vacuum_db.synchronous=OFF");
  if( rc!=SQLITE_OK ){

    if( rc!=SQLITE_OK ) goto end_of_vacuum;
#ifndef SQLITE_OMIT_AUTOVACUUM
    sqlite3BtreeSetAutoVacuum(pMain, sqlite3BtreeGetAutoVacuum(pTemp));
#endif
  }

  if( rc==SQLITE_OK ){
    rc = sqlite3BtreeSetPageSize(pMain, sqlite3BtreeGetPageSize(pTemp), nRes,1);
  }

end_of_vacuum:
  /* Restore the original value of db->flags */
  db->flags = saved_flags;
  db->nChange = saved_nChange;
  db->nTotalChange = saved_nTotalChange;