Hey again,

I´m trying to update the data of a specific key/data pair. The problem is
that i does not do that. I use the put() method to store the new DBT in the
database. The only thing I do is changing the data part of the DBT and stor
it again.
Is this the right way or should I delete the specific DBT from the database
and store a new DBT but with the same Key?

Here is my code (the code compiles and links properly, but does not update
the DBT):

Db db(0,0);
db.open(NULL,"the_db.db",NULL,DB_BTREE,DB_CREATE,0 664);

try
{
Dbt key;
Dbt data;
memset(&key,0,sizeof(key));
memset(&data,0,sizeof(data));
key.set_data("0");
key.set_size(sizeof("0"));

ret = db.get(NULL,&key,&data,0);
if(ret == 0)
{
char *the_data = (char *)data.get_data();
}
else if(ret = EINVAL)
{
std::cout << "error: EINVAL" << "\n";
}

data.set_data("0");
data.set_size(sizeof("0"));

ret = db.put(0,&key,&data,0);
if(ret == 0)
{
std::cout << "updated succesfull.\n";
}
else if(ret == EACCES)
{
std::cout << "error: EACCES\n";
}
else if(ret == EINVAL)
{
std::cout << "error: EINVAL\n";
}
}
catch (DbException &dbe) {
std::cerr << "Exception: " << dbe.what() << "\n";
}
db.close(0);


Thanks in advance!
/Bogdan

Hey,

I have found a way around the earlier problem, but now I have another
problem.
When I retrieve a specific DBT and want to display the data (from the
key/data pair) then it only shows a part of the string I stored in the
database.

Here is my code:

//=========================================
//Storing the DBT
//=========================================

int ret;

Db db(0,0);
db.set_error_stream(&std::cerr);
db.set_errpfx("Persistens");
db.set_pagesize(1024); /* Page size: 1K. */
db.set_cachesize(0,32 * 1024,0);
db.open(NULL,"Test.db",NULL,DB_BTREE,DB_CREATE,066 4);

try
{
Dbt key;
Dbt data;
memset(&key,0,sizeof(key));
memset(&data,0,sizeof(data));
key.set_flags(DB_DBT_MALLOC);
data.set_flags(DB_DBT_MALLOC);

key.set_data("Test");
key.set_size(sizeof("Test"));
data.set_data(indData);
data.set_size(sizeof(indData));

ret = db.put(0,&key,&data,0);
if(ret == 0)
{
std::cout << "Saved: " << indData << "\n";
}
}
catch (DbException &dbe) {
std::cout << "Persistens: " << dbe.what() << "\n";
}

db.sync(0);
db.close(0);


//=========================================
//Retrieving the DBT
//=========================================

int ret;

Db db(0,0);
db.open(NULL,"Test.db",NULL,DB_BTREE,DB_CREATE,066 4);

try
{
Dbt key;
Dbt data;
memset(&key,0,sizeof(key));
memset(&data,0,sizeof(data));
key.set_flags(DB_DBT_MALLOC);
data.set_flags(DB_DBT_MALLOC);

Dbc *dbcp;
db.cursor(NULL, &dbcp, 0);

key.set_data("Test");
key.set_size(sizeof("Test"));

ret = dbcp->get(&key, &data, DB_SET);
if(ret == 0)
{
char *text = (char *)data.get_data();
std::cout << text << std::endl;
}

dbcp->close();
}
catch (DbException &dbe) {
std::cout << "Persistens: " << dbe.what() << "\n";
}

db.close(0);