SQLite

      }else if( isOpen==0 ){
#ifdef SQLITE_DEFAULT_WAL_SAFETYLEVEL
        /* Default to specified safety_level for WAL mode */
        if( pBt->db!=0 && pBt->db->aDb!=0 ){
          int iDb;
          sqlite3 *db = pBt->db;
          Db *aDb = db->aDb;
          u8 level = 0;
          for(iDb=0; iDb<db->nDb; iDb++){
            if( aDb[iDb].pBt && aDb[iDb].pBt->pBt==pBt ) break;
          }
          assert( iDb<db->nDb );
          level = db->aDb[iDb].safety_level;
          if( !SQLITE_DbSafetyLevelIsFixed(level) && 
             (SQLITE_DbSafetyLevelValue(level) != SQLITE_DEFAULT_WAL_SAFETYLEVEL) ){
            aDb[iDb].safety_level = SQLITE_DEFAULT_WAL_SAFETYLEVEL;
            sqlite3PagerSetSafetyLevel(pBt->pPager, SQLITE_DEFAULT_WAL_SAFETYLEVEL, 
                                       (db->flags&SQLITE_FullFSync)!=0,
                                       (db->flags&SQLITE_CkptFullFSync)!=0);
          }
        }
#endif

    }
    if( eMode==PAGER_JOURNALMODE_QUERY && pId2->n==0 ){
      /* Convert "PRAGMA journal_mode" into "PRAGMA main.journal_mode" */
      iDb = 0;
      pId2->n = 1;
    }
#ifdef SQLITE_DEFAULT_WAL_SAFETYLEVEL
    if( ! SQLITE_DbSafetyLevelIsFixed(pDb->safety_level) ){
      if( eMode == PAGER_JOURNALMODE_WAL ){
        /* when entering wal mode, immediately switch the safety_level
        ** so that a query to pragma synchronous returns the correct value */
      
        pDb->safety_level = SQLITE_DEFAULT_WAL_SAFETYLEVEL;
      }else{
        /* If the user hasn't overridden the synchronous setting, use the 
        ** default for non-wal databases */
        pDb->safety_level = 3;
      }
    }
#endif /* SQLITE_DEFAULT_WAL_SAFETYLEVEL */
    for(ii=db->nDb-1; ii>=0; ii--){
      if( db->aDb[ii].pBt && (ii==iDb || pId2->n==0) ){
        sqlite3VdbeUsesBtree(v, ii);
        sqlite3VdbeAddOp3(v, OP_JournalMode, ii, 1, eMode);
      }

  ** the local value does not make changes to the disk file and the
  ** default value will be restored the next time the database is
  ** opened.
  */
  if( sqlite3StrICmp(zLeft,"synchronous")==0 ){
    if( sqlite3ReadSchema(pParse) ) goto pragma_out;
    if( !zRight ){
      u8 level = pDb->safety_level;
      i64 safetyLevel = (i64)(SQLITE_DbSafetyLevelValue(level)-1);
      returnSingleInt(pParse, "synchronous", &safetyLevel);
    }else{
      if( !db->autoCommit ){
        sqlite3ErrorMsg(pParse, 
            "Safety level may not be changed inside a transaction");
      }else{
        u8 level = getSafetyLevel(zRight)+1;
        pDb->safety_level = (level | SQLITE_SAFETYLEVEL_FIXED);
      }
    }
  }else
#endif /* SQLITE_OMIT_PAGER_PRAGMAS */

#ifndef SQLITE_OMIT_FLAG_PRAGMAS
  if( flagPragma(pParse, zLeft, zRight) ){

  /*
  ** Reset the safety level, in case the fullfsync flag or synchronous
  ** setting changed.
  */
#ifndef SQLITE_OMIT_PAGER_PRAGMAS
  if( db->autoCommit ){
    sqlite3BtreeSetSafetyLevel(pDb->pBt, SQLITE_DbSafetyLevelValue(pDb->safety_level),
               (db->flags&SQLITE_FullFSync)!=0,
               (db->flags&SQLITE_CkptFullFSync)!=0);
  }
#endif
pragma_out:
  sqlite3DbFree(db, zLeft);
  sqlite3DbFree(db, zRight);
}

#endif /* SQLITE_OMIT_PRAGMA */

#include "vdbe.h"
#include "pager.h"
#include "pcache.h"

#include "os.h"
#include "mutex.h"

/* When using a default wal safety level, the safety level should only 
** change with the journal mode if the user hasn't manually specified 
** pragma synchronous, if they have the defaults shouldn't be applied.
** The SQLITE_SAFETYLEVEL_FIXED value is ORed into the Db->safety_level
** field when the user has specified a synchronous setting via pragma.
*/
#define SQLITE_SAFETYLEVEL_FIXED 0x10
#define SQLITE_SAFETYLEVEL_VALUE_MASK 0x03
#define SQLITE_DbSafetyLevelValue(level) (level&SQLITE_SAFETYLEVEL_VALUE_MASK)
#define SQLITE_DbSafetyLevelIsFixed(level) (level&SQLITE_SAFETYLEVEL_FIXED)

/*
** Each database file to be accessed by the system is an instance
** of the following structure.  There are normally two of these structures
** in the sqlite.aDb[] array.  aDb[0] is the main database file and
** aDb[1] is the database file used to hold temporary tables.  Additional
** databases may be attached.