Cannot use multiple database in my application

Question

I have written a C++/CLI wrapper for use berkeleydb without lost performance. This wrapper run perfectly with one database but when i open a second database ( i create a new instance of the wrapper ) the application crash.
I have written a minimal pure C++ application that use the pure C++ classe of my wrapper, when a open and use only one database the code run perfectly but with two databases, the application be crazy.
infos : compiler VC++ 2008, OS : Vista 32bit
this the code of my berkeleydb class :
#pragma comment (lib, "libdb47.lib")
#if defined(WIN32) || defined(WIN64)
#include <windows.h>
#include <list>
#endif
#ifndef ParamsStructCpp
#include "ParamsStruct.h"
#endif
#include <db_cxx.h>
#include "BerkeleyMethods.h"
using namespace std;
using namespace stdext;
// type
//typedef list<ParamsStructCpp>::iterator it;
typedef list<ParamsStructCpp> fetchbuffer;
// Db objects
Db * db; // Database object
DbEnv env(0); // Environment for transaction
u_int32_t oFlags = DB_CREATE|DB_AUTO_COMMIT|DB_READ_UNCOMMITTED; // Open flags; //
u_int32_t env_oFlags = DB_CREATE |
DB_THREAD |
                         DB_INIT_LOCK |
                         DB_INIT_LOG |
                         DB_INIT_MPOOL |
                         DB_INIT_TXN |
                         DB_MULTIVERSION; // Flags for environement
// Constructeurs
BerkeleyMethods::BerkeleyMethods()
BerkeleyMethods::BerkeleyMethods(char * dbname, unsigned int db_cache_gbyte, unsigned int db_cache_size,
                    int db_cache_number, int db_type, char * dberr_file, char * envdir, unsigned int dbtxn_timeout,
                         unsigned int dbtxn_max)
     strcpy_s(this->db_name, strlen(_db_name)+1, dbname);
     this->db_cache_gbyte = db_cache_gbyte;
this->db_cache_size = db_cache_size;
     this->db_cache_number = db_cache_number;
this->db_type = db_type;
     this->db_txn_timeout = dbtxn_timeout;
     this->db_txn_max = dbtxn_max;
     strcpy_s(this->db_err_file, strlen(_db_err_file)+1, dberr_file);
     strcpy_s(this->env_dir, strlen(_env_dir)+1, envdir);
     this->Set_restoremode(false);
// ==========
// Fonctions
// http://www.codeproject.com/KB/string/UtfConverter.aspx
bool BerkeleyMethods::OpenDatabase()
     try
          std::cout << "Dbname " << this->db_name << std::endl;
          if (strlen(this->db_name) < 2) {
throw new std::exception("Database name is unset");
          // Set database cache
          env.set_cachesize(this->db_cache_gbyte, this->db_cache_size, this->db_cache_number);
          // Set transaction timeout
          if (this->db_txn_timeout > 0) {
               env.set_timeout(this->db_txn_timeout, DB_SET_TXN_TIMEOUT);
// Set max opened transactions
          if (this->db_txn_max > 0) {
               env.set_tx_max(this->db_txn_max);
          // Dupplicate key support;
          if (this->Get_dup_support()) {
env_oFlags = env_oFlags|DB_DUPSORT;
          // Deadlokcs gesture
          env.set_lk_detect(DB_LOCK_MINWRITE);
// Set the error file
          env.set_errfile(fopen(this->db_err_file, "w+"));
// Error prefix
          env.set_errpfx("Error > ");
          // Open environement
          env.open(this->env_dir, env_oFlags, 0);
          // Create database object
          db = new Db(&env, 0);
          // Open the database
          switch(this->db_type)
          case 1:
               db->open(NULL, this->db_name, NULL, DB_BTREE, oFlags, 0);
               break;
          case 2:
               db->open(NULL, this->db_name, NULL, DB_HASH, oFlags, 0);
               break;
          case 3:
               db->open(NULL, this->db_name, NULL, DB_QUEUE, oFlags, 0);
               break;
          case 4:
               db->open(NULL, this->db_name, NULL, DB_RECNO, oFlags, 0);
               break;
          default:
               throw new std::exception("Database name is unset");
               break;
          u_int32_t gbcacheSize = 0;
u_int32_t bytecacheSize=0;
int ncache=0;
env.get_cachesize(&gbcacheSize,&bytecacheSize,&ncache);
std::cerr << "Taille du cache est:" << gbcacheSize << "Go plus " << bytecacheSize << " octets." << std::endl;
std::cerr << "Number of caches : " << ncache << std::endl;
          return true;
     catch(DbException &e)
          std::cout << e.what() << std::endl;
     catch(std::exception &e)
          std::cout << e.what() << std::endl;
     return false;
bool BerkeleyMethods::CloseDatabase()
     try
          db->close(0);
          env.close(0);
          return true;
     catch(DbException &e)
          std::cout << e.what() << std::endl;
     catch(std::exception &e)
          std::cout << e.what() << std::endl;
     return false;
bool BerkeleyMethods::AddData(char * key, unsigned long int value)
     if (this->Get_restoremode())
          return false;
     DbTxn * txn;
     try
          env.txn_begin(NULL, &txn, 0); // Bebin transaction
          // Set datas
Dbt _key(key, strlen(key)+1);
Dbt _value(&value, sizeof(unsigned long int));
          env.txn_checkpoint(512, 2, 0);
          int exist = db->put(txn, &_key, &_value, DB_NOOVERWRITE);
          if (exist == DB_KEYEXIST) {
               std::cout << "This record already exist" << std::endl;
          txn->commit(0);
          return true;
     catch(DbException &e)
          std::cout << e.what() << std::endl;
          txn->abort();
     catch(...)
          std::cout << "Error" << std::endl;
          txn->abort();
     return false;
bool BerkeleyMethods::AddData(unsigned long int key, char * value)
     if (this->Get_restoremode())
          return false;
     DbTxn * txn;
     try
          env.txn_begin(NULL, &txn, 0); // Bebin transaction
Dbt _key(&key, sizeof(unsigned long int));
          Dbt _value(value, strlen(value)+1);
          env.txn_checkpoint(512, 2, 0);
          int exist = db->put(txn, &_key, &_value, DB_NOOVERWRITE);
          if (exist == DB_KEYEXIST) {
               std::cout << "This record already exist" << std::endl;
          txn->commit(0);     
          return true;
     catch(DbException &e)
          std::cout << e.what() << std::endl;
          txn->abort();
     catch(...)
          txn->abort();
     return false;
bool BerkeleyMethods::AddData(char * key, char * value)
     if (this->Get_restoremode())
          return false;
     DbTxn * txn;
     try
          env.txn_begin(NULL, &txn, 0); // Bebin transaction
Dbt _key(key, strlen(key)+1);
          Dbt _value(value, strlen(value)+1);
          env.txn_checkpoint(512, 2, 0);
          int exist = db->put(txn, &_key, &_value, DB_NOOVERWRITE);
          if (exist == DB_KEYEXIST) {
               std::cout << "This record already exist" << std::endl;
          txn->commit(0);     
          return true;
     catch(DbException &e)
          std::cout << e.what() << std::endl;
          txn->abort();
     catch(...)
          txn->abort();
     return false;
bool BerkeleyMethods::AddData(unsigned long int key, unsigned long int value)
     if (this->Get_restoremode())
          return false;
     DbTxn * txn;
     try
          env.txn_begin(NULL, &txn, 0); // Bebin transaction
Dbt _key(&key, sizeof(unsigned long int));
          Dbt _value(&value, sizeof(unsigned long int));
          env.txn_checkpoint(512, 2, 0);
          int exist = db->put(txn, &_key, &_value, DB_NOOVERWRITE);
          if (exist == DB_KEYEXIST) {
               std::cout << "This record already exist" << std::endl;
          txn->commit(0);     
          return true;
     catch(DbException &e)
          std::cout << e.what() << std::endl;
          txn->abort();
     catch(...)
          txn->abort();
     return false;
bool BerkeleyMethods::AddData(char * key, ParamsStructCpp value)
     if (this->Get_restoremode())
          return false;
     DbTxn * txn;
     try
          env.txn_begin(NULL, &txn, 0); // Bebin transaction
Dbt _key(key, strlen(key)+1);
          Dbt _value(&value, sizeof(ParamsStructCpp));
          env.txn_checkpoint(512, 2, 0);
          int exist = db->put(txn, &_key, &_value, DB_NOOVERWRITE);
          if (exist == DB_KEYEXIST) {
               std::cout << "This record already exist" << std::endl;
          txn->commit(0);     
          return true;
     catch(DbException &e)
          std::cout << e.what() << std::endl;
          txn->abort();
     catch(...)
          txn->abort();
     return false;
bool BerkeleyMethods::AddData(unsigned long int key, struct ParamsStructCpp value)
     if (this->Get_restoremode())
          return false;
     DbTxn * txn;
     try
          env.txn_begin(NULL, &txn, 0); // Bebin transaction
Dbt _key(&key, sizeof(unsigned long int));
          Dbt _value(&value, sizeof(ParamsStructCpp));
          env.txn_checkpoint(512, 2, 0);
          int exist = db->put(txn, &_key, &_value, DB_NOOVERWRITE);
          if (exist == DB_KEYEXIST) {
               std::cout << "This record already exist" << std::endl;
          txn->commit(0);     
          return true;
     catch(DbException &e)
          std::cout << e.what() << std::endl;
          txn->abort();
     catch(...)
          txn->abort();
     return false;
bool BerkeleyMethods::Exist(unsigned long int key)
     if (this->Get_restoremode())
          return true;
     DbTxn * txn;
     try
          env.txn_begin(NULL, &txn, DB_TXN_SNAPSHOT); // Bebin transaction
Dbt _key(&key, sizeof(unsigned long int));
          int state = db->exists(txn, &_key, DB_READ_COMMITTED);
          txn->commit(0);
          if (state == 0) {
               return true;
     catch(DbException &e)
          std::cout << e.what() << std::endl;
          txn->abort();
     catch(...)
          txn->abort();
     return false;
bool BerkeleyMethods::Exist(char * key)
     if (this->Get_restoremode())
          return true;
     DbTxn * txn;
     try
          env.txn_begin(NULL, &txn, DB_TXN_SNAPSHOT); // Bebin transaction
          Dbt _key(key, strlen(key)+1);
          int state = db->exists(txn, &_key,DB_READ_COMMITTED);
          txn->commit(0);
          if (state == 0) {
               return true;
     catch(DbException &e)
          std::cout << e.what() << std::endl;
          txn->abort();
     catch(...)
          txn->abort();
     return false;
void BerkeleyMethods::GetData (char * pData, int nbr, unsigned long int key)
     if (this->Get_restoremode())
          return;
     DbTxn * txn;
     Dbc *dbcp;
     try
env.txn_begin(NULL, &txn, DB_TXN_SNAPSHOT); // Bebin transaction
          db->cursor(txn, &dbcp, 0);
          Dbt _key;
          Dbt data;
          key.setdata(&key);
          key.setsize(sizeof(unsigned long int));
          dbcp->get(&_key, &data, DB_FIRST);
          char * temp = (char *)data.get_data();
strcpy_s(pData, strlen(temp)+1, temp);
          dbcp->close();
          txn->commit(0);
     catch(DbException &e)
          std::cout << e.what() << std::endl;
          if (dbcp != NULL)
               dbcp->close();
          if (txn != NULL)
               txn->abort();
     catch(...)
          if (dbcp != NULL)
               dbcp->close();
          if (txn != NULL)
               txn->abort();
unsigned long int BerkeleyMethods::GetData(char * key)
     if (this->Get_restoremode())
          return 0;
     DbTxn * txn;
     Dbc *dbcp;
     try
env.txn_begin(NULL, &txn, DB_TXN_SNAPSHOT); // Bebin transaction
          db->cursor(txn, &dbcp, 0);
Dbt _key;
          Dbt data;
          key.setdata(key);
          key.setulen(strlen(key)+1);
          dbcp->get(&_key, &data, DB_FIRST);
unsigned long int xdata = *((unsigned long int *)data.get_data());
          dbcp->close();
          txn->commit(0);
          return xdata;
     catch(DbException &e)
          std::cout << e.what() << std::endl;
          dbcp->close();
          txn->abort();
     catch(...)
          dbcp->close();
          txn->abort();
     return 0;
ParamsStructCpp * BerkeleyMethods::GetData(unsigned long int key, bool null)
     if (this->Get_restoremode()) {
          return new ParamsStructCpp();
     DbTxn * txn;
     Dbc *dbcp;
     try
env.txn_begin(NULL, &txn, DB_TXN_SNAPSHOT); // Bebin transaction
          db->cursor(txn, &dbcp, 0);
          Dbt _key;
          Dbt data;
          key.setdata(&key);
          key.setsize(sizeof(unsigned long int));
dbcp->get(&_key, &data, DB_FIRST);
          ParamsStructCpp * temp = (ParamsStructCpp *)data.get_data();
          dbcp->close();
          txn->commit(0);
          return temp;
     catch(DbException &e)
          std::cout << e.what() << std::endl;
          dbcp->close();
          txn->abort();
     catch(...)
          dbcp->close();
          txn->abort();
     return new ParamsStructCpp();
ParamsStructCpp * BerkeleyMethods::GetData(char * key, bool null)
     if (this->Get_restoremode()) {
          return new ParamsStructCpp();
     DbTxn * txn;
     Dbc *dbcp;
     try
env.txn_begin(NULL, &txn, DB_TXN_SNAPSHOT); // Bebin transaction
          db->cursor(txn, &dbcp, 0);
Dbt _key;
          Dbt data;
          key.setdata(key);
          key.setulen(strlen(key)+1);
          dbcp->get(&_key, &data, DB_FIRST);
ParamsStructCpp * xdata = (ParamsStructCpp *)data.get_data();
          dbcp->close();
          txn->commit(0);
          return xdata;
     catch(DbException &e)
          std::cout << e.what() << std::endl;
          dbcp->close();
          txn->abort();
     catch(...)
          dbcp->close();
          txn->abort();
     return new ParamsStructCpp();
list<ParamsStruct> BerkeleyMethods::FetchAllDatabase ()
     list<ParamsStruct> temp;
     Dbc *dbcp;
     try
          db->cursor(NULL, &dbcp, 0);
Dbt _key;
          Dbt data;
while(dbcp->get(&_key, &data, DB_NEXT))
               unsigned long int key = *((unsigned long int *)_key.get_data());
               char * datetime = (char *)data.get_data();
               ParamsStruct p;
               strcpy_s(p.lastaccess, strlen(datetime)+1, datetime);
               p.downloaded
               temp.push_back(
               //temp.insert(Tuple(datetime, key));
     catch(DbException &e)
          std::cout << e.what() << std::endl;
     catch(...)
     return temp;
bool BerkeleyMethods::DeleteData(unsigned long int key)
     if (this->Get_restoremode())
          return true;
     DbTxn * txn;
     try
          env.txn_checkpoint(128, 1, 0);
          env.txn_begin(NULL, &txn, 0); // Bebin transaction
Dbt _key;
          key.setdata(&key);
          key.setsize(sizeof(unsigned long int));
          db->del(txn, &_key, 0);
          txn->commit(0);
          return true;
     catch(DbException &e)
          std::cout << e.what() << std::endl;
          txn->abort();
     catch(...)
          txn->abort();
     return false;;
bool BerkeleyMethods::DeleteData(char * key)
     if (this->Get_restoremode())
          return true;
     DbTxn * txn;
     try
          env.txn_begin(NULL, &txn, 0); // Bebin transaction
Dbt _key;
          key.setdata(key);
          key.setulen(strlen(key)+1);
          db->del(txn, &_key, 0);
          txn->commit(0);
          return true;
     catch(DbException &e)
          std::cout << e.what() << std::endl;
          txn->abort();
     catch(...)
          txn->abort();
     return false;
int BerkeleyMethods::Sync()
     if (this->Get_restoremode())
          return -1;
     try
          return db->sync(0);
     catch(...)
return -1;
int BerkeleyMethods::Count()
     if (this->Get_restoremode())
          return -1;
     Dbc *dbcp;
     int count = 0;
     try
Dbt key;
          Dbt data;
          db->cursor(NULL, &dbcp, 0);
          while (dbcp->get(&key, &data, DB_NEXT) == 0) {
count++;
          dbcp->close();
          return count;
     catch(...)
return -1;
BerkeleyMethods::~BerkeleyMethods()
     if (db) {
     db->sync(0);
db->close(0);
     env.close(0);
=====
The code the use this class :
     BerkeleyMethods db("test.db", 0, 524288000, 1, 1, "log.txt", "./Env_dir", 1000000 * 5, 600000);
               BerkeleyMethods db1("test2.db", 0, 524288000, 1, 1, "log2.txt", "./Env_dir2", 1000000 * 5, 600000);
bool z = db.OpenDatabase();
db1.OpenDatabase();
if (z)
                    std::cout << "Base de données ouverte" << std::endl;
               for (unsigned int i = 0; i < 1000; i++)
                    ParamsStructCpp p = { 10, "02/08/2008 14:46:23", 789 };
               bool a = db.AddData(i, p);
                    db1.AddData(i, p);
if (a)
                    std::cout << "Ajout de données ok" << std::endl;
               for (unsigned int i = 0; i < 1000; i++)
                    ParamsStructCpp * c = db.GetData(i, false);
                    ParamsStructCpp * c1 = db1.GetData(i, false);
                    std::cout << "Donné récupéré " << c->downloaded << " : " << c->lastaccess << " : " << c->waittime << std::endl;
                    std::cout << "Donné récupéré " << c1->downloaded << " : " << c1->lastaccess << " : " << c1->waittime << std::endl;
/ ====
The application output show that when using two database the data is not correctly set. It seems that db and db1 is the same object :|.
For example in db i insert a key => toto with value 4, and in db1 i insert the same value nomaly have no problem. But berkeleydb say the the key toto in db1 already exist while not
I don't understand.
NB : sorry for my english

Answer 1

Michael Cahill wrote:
As a side note, it is unlikely that you want both
DB_READ_UNCOMMITTED and DB_MULTIVERSION to be set.
This combination pays a price during updates for
maintaining multiple versions, but still requires
(short term) locks to be held during reads. The BDB/XML Transaction Processing Guide states the following:
[...]in addition to BDB XML's normal degrees of isolation, you can also use snapshot isolation. This allows you to avoid the read locks that serializable isolation requires.
http://www.oracle.com/technology/documentation/berkeley-db/xml/gsg_xml_txn/cxx/isolation.html
This seems to contradict what you're saying here.
Is there a general guideline on whether or not to use MVCC together with a relaxed isolation degree like DB_READ_UNCOMMITTED? Should the statement in the BDB/XML TP Guide rather have "as an alternative to" instead of "in addition to"?
Michael Ludwig