How to delete the fist 10 recods from a table ? The problem is real.

Question

Hi,
the code below shows that deleting a records using a cursor works well, if your table is out of a environment, but if you are using a environment the things goes different. Please help me, what i am doing wrong ?
This code is the most clean code i now to do.
// THE CODE (BEGIN).
// BDBTEST.cpp : Clean code.
#include "X:\include\berkeleydb\db_cxx.h"
#define DWORD               unsigned long int
#define UINT               unsigned int
#define DB_ENV_PATH          "Z:\\Test"
#define DB_FULL_NAME     "Z:\\Test\\Test.db"
typedef     struct STRTEST
     DWORD     dwID;
     char     caTxt[64];
} strTest;
//     Functions.
int          compare_int     (     Db               *dbp,
                              const Dbt     *a,
                              const Dbt     *b);
void     Save();
void     Load();
void     DeleteAll();
//     Global variables.
DbEnv     *g_penvDbEnv;
Db          *g_pdbTest;
Dbc          *g_pdbcCursor;
Dbt          g_dbtTestKey;
Dbt          g_dbtTestData;
UINT     g_ui32ENVOpenFlags;
char     g_caError[256];
int          g_iResult;
//     Main function.
int main(int argc, char* argv[])
     g_penvDbEnv     =     NULL;
     g_pdbTest     =     NULL;
     //     First we run without environment (NO ERROR USING g_pdbcCursor->Del(0)).
     remove(DB_FULL_NAME);
     Save();
     Load();
     DeleteAll();
     Load();
     //     Now we run with environment ("Dbc::del: Invalid argument" (err_ = 22) - ERROR USING g_pdbcCursor->Del(0)).
     try
          g_penvDbEnv     =     new     DbEnv(0);
          if(g_penvDbEnv == NULL)
               return 0;
     catch(DbException &e)
          sprintf(g_caError, "ERRO -> DSDBBD: %s\n", e.what());
          return 0;
     // Set the normal flags for a transactional subsystem. Note that
     // we DO NOT specify DB_RECOVER.
     g_ui32ENVOpenFlags     =     DB_CREATE          |     // If the environment does not exist, create it.
                                   DB_INIT_LOCK     |     // Initialize locking.
                                   DB_INIT_LOG          |     // Initialize logging.
                                   DB_INIT_MPOOL     |     // Initialize the cache.
                                   DB_THREAD          |     // Free-thread the env handle.
                                   DB_INIT_TXN;          // Initialize transactions.
     //     Open/Create environment.
     try
          //     Environment settings.
          g_iResult     =     g_penvDbEnv->set_encrypt("1234", DB_ENCRYPT_AES);
          g_iResult     =     g_penvDbEnv->set_lg_bsize     (1024 * 256);                    //     LOG MEMORY FILE MAX SIZE.
          g_iResult     =     g_penvDbEnv->set_cachesize(0, 1024 * 512, 0);
          g_iResult     =     g_penvDbEnv->set_flags     (DB_AUTO_COMMIT,     1);
          g_iResult     =     g_penvDbEnv->set_flags     (DB_LOG_AUTOREMOVE,     1);
          g_iResult     =     g_penvDbEnv->set_lg_max     (1025 * 1024);                    //     LOG FILE MAX SIZE.
          // Open the environment with full transactional support.
          g_iResult     =     g_penvDbEnv->open(DB_ENV_PATH, g_ui32ENVOpenFlags, 0);
     catch(DbException &e)
          sprintf(g_caError, "ERRO -> DSDBBD: %s\n", e.what());
          return 0;
     remove(DB_FULL_NAME);
     Save();
     Load();
     DeleteAll();     //     Error goes here.
     Load();
     g_penvDbEnv->close(0);
     delete     g_penvDbEnv;
     g_penvDbEnv     =     NULL;
     return 0;
void     Save()
     int          i;
     int          iResult;
     DWORD     dwID;
     strTest     sttTest;
     if(g_penvDbEnv == NULL)
          g_pdbTest     =     new     Db(NULL, 0);
     else
          g_pdbTest     =     new     Db(g_penvDbEnv, 0);
          //     Setting databases flags     (Just use with environment).
          g_pdbTest     ->set_flags(DB_CHKSUM | DB_ENCRYPT);
     if(g_penvDbEnv == NULL)
          g_pdbTest     ->set_encrypt("1234", DB_ENCRYPT_AES);
     g_pdbTest->set_bt_compare(compare_int);
     g_iResult     =     g_pdbTest->open(NULL, DB_FULL_NAME, NULL, DB_BTREE, DB_CREATE | DB_THREAD, 0);
     dwID     =     1;
     for(i=0;i<100;i++)
          sttTest.dwID     =     dwID;
          sprintf(sttTest.caTxt, "ID = %04u", sttTest.dwID);
          g_dbtTestKey     .set_data((void*) &sttTest.dwID);
          g_dbtTestKey     .set_size(sizeof(DWORD));
          g_dbtTestData     .set_data((void*) &sttTest);
          g_dbtTestData     .set_size(sizeof(sttTest));
          iResult = g_pdbTest->put(0, &g_dbtTestKey, &g_dbtTestData, DB_NOOVERWRITE);
          dwID++;
     g_pdbTest->sync(0);
     g_pdbTest->close(0);
     delete     g_pdbTest;
     g_pdbTest     =     NULL;
void     Load()
     strTest     *psttTest;
     if(g_penvDbEnv == NULL)
          g_pdbTest     =     new     Db(NULL, 0);
     else
          g_pdbTest     =     new     Db(g_penvDbEnv, 0);
          //     Setting databases flags     (Just use with environment).
          g_pdbTest     ->set_flags(DB_CHKSUM | DB_ENCRYPT);
     if(g_penvDbEnv == NULL)
          g_pdbTest     ->set_encrypt("1234", DB_ENCRYPT_AES);
     g_pdbTest->set_bt_compare(compare_int);
     g_iResult     =     g_pdbTest->open(NULL, DB_FULL_NAME, NULL, DB_BTREE, DB_CREATE | DB_THREAD, 0);
     // Get a cursor
     g_pdbTest->cursor(NULL, &g_pdbcCursor, 0);
     // Iterate over the database, retrieving each record in turn.
     while((g_iResult = g_pdbcCursor->get(&g_dbtTestKey, &g_dbtTestData, DB_NEXT)) == 0)
          //     Get temp struct.
          psttTest     =     (strTest*)     g_dbtTestData.get_data();
     g_pdbcCursor->close();
     g_pdbTest->close(0);
     delete     g_pdbTest;
     g_pdbTest     =     NULL;
void     DeleteAll()
     strTest     *psttTest;
     try
          if(g_penvDbEnv == NULL)
               g_pdbTest     =     new     Db(NULL, 0);
          else
               g_pdbTest     =     new     Db(g_penvDbEnv, 0);
               //     Setting databases flags     (Just use with environment).
               g_pdbTest     ->set_flags(DB_CHKSUM | DB_ENCRYPT);
          if(g_penvDbEnv == NULL)
               g_pdbTest     ->set_encrypt("1234", DB_ENCRYPT_AES);
          g_pdbTest->set_bt_compare(compare_int);
          g_iResult     =     g_pdbTest->open(NULL, DB_FULL_NAME, NULL, DB_BTREE, DB_CREATE | DB_THREAD, 0);
          // Get a cursor
          g_pdbTest->cursor(NULL, &g_pdbcCursor, 0);
          // Iterate over the database, retrieving each record in turn.
          while((g_iResult = g_pdbcCursor->get(&g_dbtTestKey, &g_dbtTestData, DB_NEXT)) == 0)
               //     Get temp struct.
               psttTest     =     (strTest*)     g_dbtTestData.get_data();
               g_iResult     =     g_pdbcCursor->del(0);
     catch (DbException &dbe)
          sprintf(g_caError,     
                    "%s",
                    dbe.what());
     g_pdbcCursor->close();
     g_pdbTest->close(0);
     delete     g_pdbTest;
     g_pdbTest     =     NULL;
int compare_int(Db dbp, const Dbt a, const Dbt *b)
     int          iReturn;
     DWORD     dwKey1;
     DWORD     dwKey2;
     dwKey1     =     0;
     dwKey2     =     0;
     iReturn     =     0;
     dwKey1     =     *((DWORD*) a->get_data());
     dwKey2     =     *((DWORD*) b->get_data());
     if(dwKey1 > dwKey2)
          iReturn     =     1;
     else
          if(dwKey1 < dwKey2)
               iReturn     =     -1;
     return     iReturn;
// THE CODE (END).
Thanks,
DelNeto

Answer 1

Hi all
I solved it. No documentation about it, but the solution is to use transaction.
Just use this DeleteAll function that all works fine.
void     DeleteAll()
     strTest     *psttTest;
     DbTxn     *pTxn;
     try
          pTxn          =     NULL;
          g_pdbTest     =     NULL;
          if(g_penvDbEnv == NULL)
               g_pdbTest     =     new     Db(NULL, 0);
          else
               g_pdbTest     =     new     Db(g_penvDbEnv, 0);
               //     Setting databases flags     (Just use with environment).
               g_pdbTest     ->set_flags(DB_CHKSUM | DB_ENCRYPT);
          if(g_penvDbEnv == NULL)
               g_pdbTest     ->set_encrypt("1234", DB_ENCRYPT_AES);
          g_pdbTest->set_bt_compare(compare_int);
          g_iResult     =     g_pdbTest->open(NULL, DB_FULL_NAME, NULL, DB_BTREE, DB_CREATE | DB_THREAD, 0);
          if(g_penvDbEnv == NULL)
               g_pdbTest->cursor(NULL, &g_pdbcCursor, 0);
          else
               // Get a cursor.
               g_penvDbEnv->txn_begin(NULL, &pTxn, 0);
               g_pdbTest->cursor(pTxn, &g_pdbcCursor, 0);
          // Iterate over the database, retrieving each record in turn.
          while((g_iResult = g_pdbcCursor->get(&g_dbtTestKey, &g_dbtTestData, DB_NEXT)) == 0)
               //     Get temp struct.
               psttTest     =     (strTest*)     g_dbtTestData.get_data();
               g_iResult     =     g_pdbcCursor->del(0);
          g_pdbcCursor->close();
          if(g_penvDbEnv != NULL)
               pTxn->commit(0);
     catch (DbException &dbe)
          sprintf(g_caError,     
                    "%s",
                    dbe.what());
          g_pdbcCursor->close();
          if(g_penvDbEnv != NULL)
               pTxn->abort();
     g_pdbTest->close(0);
     delete     g_pdbTest;
     g_pdbTest     =     NULL;
Thanks to all readers,
DelNeto