SQLite

  int rc = SQLITE_OK;     /* Return code from service routines */
  Btree *pMain;           /* The database being vacuumed */
  Btree *pTemp;           /* The temporary database we vacuum into */
  char *zSql = 0;         /* SQL statements */
  int saved_flags;        /* Saved value of the db->flags */
  int saved_nChange;      /* Saved value of db->nChange */
  int saved_nTotalChange; /* Saved value of db->nTotalChange */
  void (*saved_xTrace)(void*,const char*);  /* Saved db->xTrace */
  Db *pDb = 0;            /* Database to detach at end of vacuum */
  int isMemDb;            /* True if vacuuming a :memory: database */
  int nRes;

  if( !db->autoCommit ){
    sqlite3SetString(pzErrMsg, db, "cannot VACUUM from within a transaction");
    return SQLITE_ERROR;
  }

  /* Save the current value of the database flags so that it can be 
  ** restored before returning. Then set the writable-schema flag, and
  ** disable CHECK and foreign key constraints.  */
  saved_flags = db->flags;
  saved_nChange = db->nChange;
  saved_nTotalChange = db->nTotalChange;
  saved_xTrace = db->xTrace;
  db->flags |= SQLITE_WriteSchema | SQLITE_IgnoreChecks;
  db->flags &= ~SQLITE_ForeignKeys;
  db->xTrace = 0;

  pMain = db->aDb[0].pBt;
  isMemDb = sqlite3PagerIsMemdb(sqlite3BtreePager(pMain));

  /* 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

  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;
  db->xTrace = saved_xTrace;

  /* Currently there is an SQL level transaction open on the vacuum
  ** database. No locks are held on any other files (since the main file
  ** was committed at the btree level). So it safe to end the transaction
  ** by manually setting the autoCommit flag to true and detaching the
  ** vacuum database. The vacuum_db journal file is deleted when the pager
  ** is closed by the DETACH.

do_test trace-2.4 {
  execsql {SELECT * FROM t1}
} {1 2 2 3 2 3}
do_test trace-2.5 {
  set TRACE_OUT
} {SELECT * FROM t1}
catch {sqlite3_finalize $STMT}

do_test trace-2.6 {
  set TRACE_OUT {}
  db eval VACUUM
  set TRACE_OUT
} {VACUUM}

# Similar tests, but this time for profiling.
# 
do_test trace-3.1 {
  set rc [catch {db profile 1 2 3} msg]
  lappend rc $msg
} {1 {wrong # args: should be "db profile ?CALLBACK?"}}