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Comment:Add comment to speculate when setting journal_mode=OFF on VACUUM does not help performance. No changes to code. (CVS 5071)
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SHA1: 9c8b4babb2222a5e0c2ecf7a116b7df90084c81d
User & Date: drh 2008-04-30 16:38:23.000
Context
2008-05-01
02:47
Test versions of getVarint functions. The updates essentially utilize loop unrolling and some shifting/anding tricks to minimize the number of logical operations required. (CVS 5072) (check-in: 682dc24dbe user: shane tags: trunk)
2008-04-30
16:38
Add comment to speculate when setting journal_mode=OFF on VACUUM does not help performance. No changes to code. (CVS 5071) (check-in: 9c8b4babb2 user: drh tags: trunk)
15:55
Improved option handling in speedtest8.c. Added -quiet and -priority options. Added reporting of total user and system time. (CVS 5070) (check-in: aa59974ec1 user: shane tags: trunk)
Changes
Unified Diff Ignore Whitespace Patch
Changes to src/vacuum.c.
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**
*************************************************************************
** 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 1.77 2008/03/20 11:04:21 danielk1977 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.








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**
*************************************************************************
** 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 1.78 2008/04/30 16:38:23 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.
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  /* Attach the temporary database as 'vacuum_db'. The synchronous pragma
  ** can be set to 'off' for this file, as it is not recovered if a crash
  ** occurs anyway. The integrity of the database is maintained by a
  ** (possibly synchronous) transaction opened on the main database before
  ** sqlite3BtreeCopyFile() is called.
  **
  ** An optimisation would be to use a non-journaled pager.






  */
  zSql = "ATTACH '' AS vacuum_db;";
  rc = execSql(db, zSql);
  if( rc!=SQLITE_OK ) goto end_of_vacuum;
  pDb = &db->aDb[db->nDb-1];
  assert( strcmp(db->aDb[db->nDb-1].zName,"vacuum_db")==0 );
  pTemp = db->aDb[db->nDb-1].pBt;








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  /* Attach the temporary database as 'vacuum_db'. The synchronous pragma
  ** can be set to 'off' for this file, as it is not recovered if a crash
  ** occurs anyway. The integrity of the database is maintained by a
  ** (possibly synchronous) transaction opened on the main database before
  ** sqlite3BtreeCopyFile() is called.
  **
  ** An optimisation would be to use a non-journaled pager.
  ** (Later:) I tried setting "PRAGMA vacuum_db.journal_mode=OFF" but
  ** that actually made the VACUUM run slower.  Very little journalling
  ** actually occurs when doing a vacuum since the vacuum_db is initially
  ** empty.  Only the journal header is written.  Apparently it takes more
  ** time to parse and run the PRAGMA to turn journalling off than it does
  ** to write the journal header file.
  */
  zSql = "ATTACH '' AS vacuum_db;";
  rc = execSql(db, zSql);
  if( rc!=SQLITE_OK ) goto end_of_vacuum;
  pDb = &db->aDb[db->nDb-1];
  assert( strcmp(db->aDb[db->nDb-1].zName,"vacuum_db")==0 );
  pTemp = db->aDb[db->nDb-1].pBt;
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