vdbeaux.c

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** has been modified, "trip" or invalidate each cursor in
** that Btree might have been modified so that the cursor
** can never be used again.  This happens when a rollback
*** occurs.  We have to trip all the other cursors, even
** cursor from other VMs in different database connections,
** so that none of them try to use the data at which they
** were pointing and which now may have been changed due
** to the rollback.
**
** Remember that a rollback can delete tables complete and
** reorder rootpages.  So it is not sufficient just to save
** the state of the cursor.  We have to invalidate the cursor
** so that it is never used again.
*/
static void invalidateCursorsOnModifiedBtrees(sqlite3 *db){
  int i;
  for(i=0; i<db->nDb; i++){
    Btree *p = db->aDb[i].pBt;
    if( p && sqlite3BtreeIsInTrans(p) ){
      sqlite3BtreeTripAllCursors(p, SQLITE_ABORT);
    }
  }
}

/*
** This routine is called the when a VDBE tries to halt.  If the VDBE
** has made changes and is in autocommit mode, then commit those
** changes.  If a rollback is needed, then do the rollback.
**
** This routine is the only way to move the state of a VM from
** SQLITE_MAGIC_RUN to SQLITE_MAGIC_HALT.  It is harmless to
** call this on a VM that is in the SQLITE_MAGIC_HALT state.
**
** Return an error code.  If the commit could not complete because of
** lock contention, return SQLITE_BUSY.  If SQLITE_BUSY is returned, it
** means the close did not happen and needs to be repeated.
*/
int sqlite3VdbeHalt(Vdbe *p){
  sqlite3 *db = p->db;
  int i;
  int (*xFunc)(Btree *pBt) = 0;  /* Function to call on each btree backend */
  int isSpecialError;            /* Set to true if SQLITE_NOMEM or IOERR */

  /* This function contains the logic that determines if a statement or
  ** transaction will be committed or rolled back as a result of the
  ** execution of this virtual machine. 
  **
  ** If any of the following errors occur:
  **
  **     SQLITE_NOMEM
  **     SQLITE_IOERR
  **     SQLITE_FULL
  **     SQLITE_INTERRUPT
  **
  ** Then the internal cache might have been left in an inconsistent
  ** state.  We need to rollback the statement transaction, if there is
  ** one, or the complete transaction if there is no statement transaction.
  */

  if( p->db->mallocFailed ){
    p->rc = SQLITE_NOMEM;
  }
  closeAllCursorsExceptActiveVtabs(p);
  if( p->magic!=VDBE_MAGIC_RUN ){
    return SQLITE_OK;
  }
  checkActiveVdbeCnt(db);

  /* No commit or rollback needed if the program never started */
  if( p->pc>=0 ){
    int mrc;   /* Primary error code from p->rc */

    /* Lock all btrees used by the statement */
    sqlite3BtreeMutexArrayEnter(&p->aMutex);

    /* Check for one of the special errors */
    mrc = p->rc & 0xff;
    isSpecialError = mrc==SQLITE_NOMEM || mrc==SQLITE_IOERR
                     || mrc==SQLITE_INTERRUPT || mrc==SQLITE_FULL;
    if( isSpecialError ){
      /* This loop does static analysis of the query to see which of the
      ** following three categories it falls into:
      **
      **     Read-only
      **     Query with statement journal
      **     Query without statement journal
      **
      ** We could do something more elegant than this static analysis (i.e.
      ** store the type of query as part of the compliation phase), but 
      ** handling malloc() or IO failure is a fairly obscure edge case so 
      ** this is probably easier. Todo: Might be an opportunity to reduce 
      ** code size a very small amount though...
      */
      int notReadOnly = 0;
      int isStatement = 0;
      assert(p->aOp || p->nOp==0);
      for(i=0; i<p->nOp; i++){ 
        switch( p->aOp[i].opcode ){
          case OP_Transaction:
            notReadOnly |= p->aOp[i].p2;
            break;
          case OP_Statement:
            isStatement = 1;
            break;
        }
      }

   
      /* If the query was read-only, we need do no rollback at all. Otherwise,
      ** proceed with the special handling.
      */
      if( notReadOnly || mrc!=SQLITE_INTERRUPT ){
        if( p->rc==SQLITE_IOERR_BLOCKED && isStatement ){
          xFunc = sqlite3BtreeRollbackStmt;
          p->rc = SQLITE_BUSY;
        } else if( (mrc==SQLITE_NOMEM || mrc==SQLITE_FULL) && isStatement ){
          xFunc = sqlite3BtreeRollbackStmt;
        }else{
          /* We are forced to roll back the active transaction. Before doing
          ** so, abort any other statements this handle currently has active.
          */
          invalidateCursorsOnModifiedBtrees(db);
          sqlite3RollbackAll(db);
          db->autoCommit = 1;
        }
      }
    }
  
    /* If the auto-commit flag is set and this is the only active vdbe, then
    ** we do either a commit or rollback of the current transaction. 
    **
    ** Note: This block also runs if one of the special errors handled 
    ** above has occured. 
    */
    if( db->autoCommit && db->activeVdbeCnt==1 ){
      if( p->rc==SQLITE_OK || (p->errorAction==OE_Fail && !isSpecialError) ){
        /* The auto-commit flag is true, and the vdbe program was 
        ** successful or hit an 'OR FAIL' constraint. This means a commit 
        ** is required.
        */
        int rc = vdbeCommit(db);
        if( rc==SQLITE_BUSY ){
          sqlite3BtreeMutexArrayLeave(&p->aMutex);
          return SQLITE_BUSY;
        }else if( rc!=SQLITE_OK ){
          p->rc = rc;
          sqlite3RollbackAll(db);
        }else{
          sqlite3CommitInternalChanges(db);
        }
      }else{
        sqlite3RollbackAll(db);
      }
    }else if( !xFunc ){
      if( p->rc==SQLITE_OK || p->errorAction==OE_Fail ){
        if( p->openedStatement ){
          xFunc = sqlite3BtreeCommitStmt;
        } 
      }else if( p->errorAction==OE_Abort ){
        xFunc = sqlite3BtreeRollbackStmt;
      }else{
        invalidateCursorsOnModifiedBtrees(db);
        sqlite3RollbackAll(db);
        db->autoCommit = 1;
      }
    }
  
    /* If xFunc is not NULL, then it is one of sqlite3BtreeRollbackStmt or
    ** sqlite3BtreeCommitStmt. Call it once on each backend. If an error occurs
    ** and the return code is still SQLITE_OK, set the return code to the new
    ** error value.
    */
    assert(!xFunc ||
      xFunc==sqlite3BtreeCommitStmt ||
      xFunc==sqlite3BtreeRollbackStmt
    );
    for(i=0; xFunc && i<db->nDb; i++){ 
      int rc;
      Btree *pBt = db->aDb[i].pBt;
      if( pBt ){
        rc = xFunc(pBt);
        if( rc && (p->rc==SQLITE_OK || p->rc==SQLITE_CONSTRAINT) ){
          p->rc = rc;
          sqlite3SetString(&p->zErrMsg, 0);
        }
      }
    }
  
    /* If this was an INSERT, UPDATE or DELETE and the statement was committed, 
    ** set the change counter. 
    */
    if( p->changeCntOn && p->pc>=0 ){
      if( !xFunc || xFunc==sqlite3BtreeCommitStmt ){
        sqlite3VdbeSetChanges(db, p->nChange);
      }else{
        sqlite3VdbeSetChanges(db, 0);
      }
      p->nChange = 0;
    }
  
    /* Rollback or commit any schema changes that occurred. */
    if( p->rc!=SQLITE_OK && db->flags&SQLITE_InternChanges ){
      sqlite3ResetInternalSchema(db, 0);
      db->flags = (db->flags | SQLITE_InternChanges);
    }

    /* Release the locks */
    sqlite3BtreeMutexArrayLeave(&p->aMutex);
  }

  /* We have successfully halted and closed the VM.  Record this fact. */
  if( p->pc>=0 ){
    db->activeVdbeCnt--;
  }
  p->magic = VDBE_MAGIC_HALT;
  checkActiveVdbeCnt(db);
  if( p->db->mallocFailed ){
    p->rc = SQLITE_NOMEM;
  }
  checkActiveVdbeCnt(db);

  return SQLITE_OK;
}


/*
** Each VDBE holds the result of the most recent sqlite3_step() call
** in p->rc.  This routine sets that result back to SQLITE_OK.
*/
void sqlite3VdbeResetStepResult(Vdbe *p){
  p->rc = SQLITE_OK;
}

/*
** Clean up a VDBE after execution but do not delete the VDBE just yet.
** Write any error messages into *pzErrMsg.  Return the result code.
**
** After this routine is run, the VDBE should be ready to be executed
** again.
**
** To look at it another way, this routine resets the state of the
** virtual machine from VDBE_MAGIC_RUN or VDBE_MAGIC_HALT back to
** VDBE_MAGIC_INIT.
*/
int sqlite3VdbeReset(Vdbe *p){
  sqlite3 *db;
  db = p->db;

  /* If the VM did not run to completion or if it encountered an
  ** error, then it might not have been halted properly.  So halt
  ** it now.
  */
  sqlite3SafetyOn(db);
  sqlite3VdbeHalt(p);
  sqlite3SafetyOff(db);

  /* If the VDBE has be run even partially, then transfer the error code
  ** and error message from the VDBE into the main database structure.  But
  ** if the VDBE has just been set to run but has not actually executed any
  ** instructions yet, leave the main database error information unchanged.
  */
  if( p->pc>=0 ){
    if( p->zErrMsg ){
      sqlite3ValueSetStr(db->pErr,-1,p->zErrMsg,SQLITE_UTF8,sqlite3_free);
      db->errCode = p->rc;
      p->zErrMsg = 0;
    }else if( p->rc ){
      sqlite3Error(db, p->rc, 0);
    }else{
      sqlite3Error(db, SQLITE_OK, 0);
    }
  }else if( p->rc && p->expired ){
    /* The expired flag was set on the VDBE before the first call
    ** to sqlite3_step(). For consistency (since sqlite3_step() was
    ** called), set the database error in this case as well.
    */
    sqlite3Error(db, p->rc, 0);
    sqlite3ValueSetStr(db->pErr, -1, p->zErrMsg, SQLITE_UTF8, sqlite3_free);
    p->zErrMsg = 0;
  }

  /* Reclaim all memory used by the VDBE
  */
  Cleanup(p);

  /* Save profiling information from this VDBE run.
  */
  assert( p->pTos<&p->aStack[p->pc<0?0:p->pc] || !p->aStack );
#ifdef VDBE_PROFILE
  {
    FILE *out = fopen("vdbe_profile.out", "a");
    if( out ){
      int i;
      fprintf(out, "---- ");
      for(i=0; i<p->nOp; i++){
        fprintf(out, "%02x", p->aOp[i].opcode);
      }
      fprintf(out, "\n");
      for(i=0; i<p->nOp; i++){
        fprintf(out, "%6d %10lld %8lld ",
           p->aOp[i].cnt,
           p->aOp[i].cycles,
           p->aOp[i].cnt>0 ? p->aOp[i].cycles/p->aOp[i].cnt : 0
        );
        sqlite3VdbePrintOp(out, i, &p->aOp[i]);
      }
      fclose(out);
    }
  }
#endif
  p->magic = VDBE_MAGIC_INIT;
  p->aborted = 0;
  return p->rc & db->errMask;
}
 
/*
** Clean up and delete a VDBE after execution.  Return an integer which is
** the result code.  Write any error message text into *pzErrMsg.
*/
int sqlite3VdbeFinalize(Vdbe *p){
  int rc = SQLITE_OK;
  if( p->magic==VDBE_MAGIC_RUN || p->magic==VDBE_MAGIC_HALT ){
    rc = sqlite3VdbeReset(p);
    assert( (rc & p->db->errMask)==rc );
  }else if( p->magic!=VDBE_MAGIC_INIT ){
    return SQLITE_MISUSE;
  }
  sqlite3VdbeDelete(p);
  return rc;
}

/*
** Call the destructor for each auxdata entry in pVdbeFunc for which
** the corresponding bit in mask is clear.  Auxdata entries beyond 31
** are always destroyed.  To destroy all auxdata entries, call this
** routine with mask==0.
*/
void sqlite3VdbeDeleteAuxData(VdbeFunc *pVdbeFunc, int mask){
  int i;
  for(i=0; i<pVdbeFunc->nAux; i++){
    struct AuxData *pAux = &pVdbeFunc->apAux[i];
    if( (i>31 || !(mask&(1<<i))) && pAux->pAux ){
      if( pAux->xDelete ){
        pAux->xDelete(pAux->pAux);
      }
      pAux->pAux = 0;
    }
  }
}

/*
** Delete an entire VDBE.
*/
void sqlite3VdbeDelete(Vdbe *p){
  int i;
  if( p==0 ) return;
  Cleanup(p);
  if( p->pPrev ){
    p->pPrev->pNext = p->pNext;
  }else{
    assert( p->db->pVdbe==p );
    p->db->pVdbe = p->pNext;
  }
  if( p->pNext ){
    p->pNext->pPrev = p->pPrev;
  }
  if( p->aOp ){
    for(i=0; i<p->nOp; i++){
      Op *pOp = &p->aOp[i];
      freeP3(pOp->p3type, pOp->p3);
    }
    sqlite3_free(p->aOp);
  }
  releaseMemArray(p->aVar, p->nVar);
  sqlite3_free(p->aLabel);
  sqlite3_free(p->aStack);
  releaseMemArray(p->aColName, p->nResColumn*COLNAME_N);
  sqlite3_free(p->aColName);
  sqlite3_free(p->zSql);
  p->magic = VDBE_MAGIC_DEAD;
  sqlite3_free(p);
}

/*
** If a MoveTo operation is pending on the given cursor, then do that
** MoveTo now.  Return an error code.  If no MoveTo is pending, this
** routine does nothing and returns SQLITE_OK.
*/
int sqlite3VdbeCursorMoveto(Cursor *p){
  if( p->deferredMoveto ){
    int res, rc;
#ifdef SQLITE_TEST
    extern int sqlite3_search_count;
#endif
    assert( p->isTable );
    rc = sqlite3BtreeMoveto(p->pCursor, 0, p->movetoTarget, 0, &res);
    if( rc ) return rc;
    *p->pIncrKey = 0;
    p->lastRowid = keyToInt(p->movetoTarget);
    p->rowidIsValid = res==0;
    if( res<0 ){
      rc = sqlite3BtreeNext(p->pCursor, &res);
      if( rc ) return rc;
    }
#ifdef SQLITE_TEST
    sqlite3_search_count++;
#endif
    p->deferredMoveto = 0;
    p->cacheStatus = CACHE_STALE;
  }
  return SQLITE_OK;
}

/*
** The following functions:
**
** sqlite3VdbeSerialType()
** sqlite3VdbeSerialTypeLen()
** sqlite3VdbeSerialRead()
** sqlite3VdbeSerialLen()
** sqlite3VdbeSerialWrite()
**
** encapsulate the code that serializes values for storage in SQLite
** data and index records. Each serialized value consists of a
** 'serial-type' and a blob of data. The serial type is an 8-byte unsigned
** integer, stored as a varint.
**
** In an SQLite index record, the serial type is stored directly before
** the blob of data that it corresponds to. In a table record, all serial
** types are stored at the start of the record, and the blobs of data at
** the end. Hence these functions allow the caller to handle the
** serial-type and data blob seperately.
**
** The following table describes the various storage classes for data:
**
**   serial type        bytes of data      type
**   --------------     ---------------    ---------------
**      0                     0            NULL
**      1                     1            signed integer
**      2                     2            signed integer