**
** Various scripts scan this source file in order to generate HTML
** documentation, headers files, or other derived files.  The formatting
** of the code in this file is, therefore, important.  See other comments
** in this file for details.  If in doubt, do not deviate from existing
** commenting and indentation practices when changing or adding code.
**
** $Id: vdbe.c,v 1.848 2009/06/05 16:46:53 drh Exp $
*/
#include "sqliteInt.h"
#include "vdbeInt.h"

/*
** The following global variable is incremented every time a cursor
** moves, either by the OP_SeekXX, OP_Next, or OP_Prev opcodes.  The test
................................................................................
** VMs (apart from this one), then a ROLLBACK fails.  A COMMIT fails if
** there are active writing VMs or active VMs that use shared cache.
**
** This instruction causes the VM to halt.
*/
case OP_AutoCommit: {
  int desiredAutoCommit;
  int rollback;
  int turnOnAC;

  desiredAutoCommit = pOp->p1;
  rollback = pOp->p2;
  turnOnAC = desiredAutoCommit && !db->autoCommit;
  assert( desiredAutoCommit==1 || desiredAutoCommit==0 );
  assert( desiredAutoCommit==1 || rollback==0 );
  assert( db->activeVdbeCnt>0 );  /* At least this one VM is active */

  if( turnOnAC && rollback && db->activeVdbeCnt>1 ){
    /* If this instruction implements a ROLLBACK and other VMs are
    ** still running, and a transaction is active, return an error indicating
    ** that the other VMs must complete first. 
    */
    sqlite3SetString(&p->zErrMsg, db, "cannot rollback transaction - "
        "SQL statements in progress");
    rc = SQLITE_BUSY;
  }else if( turnOnAC && !rollback && db->writeVdbeCnt>1 ){
    /* If this instruction implements a COMMIT and other VMs are writing
    ** return an error indicating that the other VMs must complete first. 
    */
    sqlite3SetString(&p->zErrMsg, db, "cannot commit transaction - "
        "SQL statements in progress");
    rc = SQLITE_BUSY;
  }else if( desiredAutoCommit!=db->autoCommit ){
    if( rollback ){
      assert( desiredAutoCommit==1 );
      sqlite3RollbackAll(db);
      db->autoCommit = 1;
    }else{
      db->autoCommit = (u8)desiredAutoCommit;
      if( sqlite3VdbeHalt(p)==SQLITE_BUSY ){
        p->pc = pc;
................................................................................
    }else{
      rc = SQLITE_ERROR;
    }
    goto vdbe_return;
  }else{
    sqlite3SetString(&p->zErrMsg, db,
        (!desiredAutoCommit)?"cannot start a transaction within a transaction":(
        (rollback)?"cannot rollback - no transaction is active":
                   "cannot commit - no transaction is active"));
         
    rc = SQLITE_ERROR;
  }
  break;
}

**
** Various scripts scan this source file in order to generate HTML
** documentation, headers files, or other derived files.  The formatting
** of the code in this file is, therefore, important.  See other comments
** in this file for details.  If in doubt, do not deviate from existing
** commenting and indentation practices when changing or adding code.
**
** $Id: vdbe.c,v 1.849 2009/06/09 18:14:18 shane Exp $
*/
#include "sqliteInt.h"
#include "vdbeInt.h"

/*
** The following global variable is incremented every time a cursor
** moves, either by the OP_SeekXX, OP_Next, or OP_Prev opcodes.  The test
................................................................................
** VMs (apart from this one), then a ROLLBACK fails.  A COMMIT fails if
** there are active writing VMs or active VMs that use shared cache.
**
** This instruction causes the VM to halt.
*/
case OP_AutoCommit: {
  int desiredAutoCommit;
  int iRollback;
  int turnOnAC;

  desiredAutoCommit = pOp->p1;
  iRollback = pOp->p2;
  turnOnAC = desiredAutoCommit && !db->autoCommit;
  assert( desiredAutoCommit==1 || desiredAutoCommit==0 );
  assert( desiredAutoCommit==1 || iRollback==0 );
  assert( db->activeVdbeCnt>0 );  /* At least this one VM is active */

  if( turnOnAC && iRollback && db->activeVdbeCnt>1 ){
    /* If this instruction implements a ROLLBACK and other VMs are
    ** still running, and a transaction is active, return an error indicating
    ** that the other VMs must complete first. 
    */
    sqlite3SetString(&p->zErrMsg, db, "cannot rollback transaction - "
        "SQL statements in progress");
    rc = SQLITE_BUSY;
  }else if( turnOnAC && !iRollback && db->writeVdbeCnt>1 ){
    /* If this instruction implements a COMMIT and other VMs are writing
    ** return an error indicating that the other VMs must complete first. 
    */
    sqlite3SetString(&p->zErrMsg, db, "cannot commit transaction - "
        "SQL statements in progress");
    rc = SQLITE_BUSY;
  }else if( desiredAutoCommit!=db->autoCommit ){
    if( iRollback ){
      assert( desiredAutoCommit==1 );
      sqlite3RollbackAll(db);
      db->autoCommit = 1;
    }else{
      db->autoCommit = (u8)desiredAutoCommit;
      if( sqlite3VdbeHalt(p)==SQLITE_BUSY ){
        p->pc = pc;
................................................................................
    }else{
      rc = SQLITE_ERROR;
    }
    goto vdbe_return;
  }else{
    sqlite3SetString(&p->zErrMsg, db,
        (!desiredAutoCommit)?"cannot start a transaction within a transaction":(
        (iRollback)?"cannot rollback - no transaction is active":
                   "cannot commit - no transaction is active"));
         
    rc = SQLITE_ERROR;
  }
  break;
}