Using a database

Hi,
I want to use a database for storing a certain information (e.g phone numbers for my contacts). I want the information to be stored even if my application is not running so when I close my application the data will still be in the database.
I tried using HSQL but I have no idea how I create my own database for creating tables. What database should I use for this purpose ? I need the database to allow me to access/update existing tables through my application.
thx.

Javaist wrote:
Hi,
I want to use a database for storing a certain information (e.g phone numbers for my contacts). I want the information to be stored even if my application is not running so when I close my application the data will still be in the database.That is how databases work.
I tried using HSQL but I have no idea how I create my own database for creating tables. What database should I use for this purpose ? Since you haven't actually provided any requirements the answer would be any database. Or even just use a file.
I need the database to allow me to access/update existing tables through my application.Any database.

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Check the following Document & Links
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http://www.geekinterview.com/question_details/1506
http://help.sap.com/saphelp_46c/helpdata/EN/35/2cd77bd7705394e10000009b387c12/frameset.htm
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http://help.sap.com/saphelp_46c/helpdata/en/9f/db9bed35c111d1829f0000e829fbfe/frameset.htm
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     if (this->Get_restoremode())
          return false;
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          if (exist == DB_KEYEXIST) {
               std::cout << "This record already exist" << std::endl;
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          std::cout << e.what() << std::endl;
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     if (this->Get_restoremode())
          return false;
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     try
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          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

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

Using a database

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