Database hangs after retrieving some records....

Question

hi,
I create a two level B+-tree index, for the first level i'm using key as logical database name, for the second level B+-tree i'm using some other field in my data. I am retrieving the records based on logical database name. I am using C++ to implement my index.
In the following code i'm retrieving records from database. Program is behaving differently for different logical database names. For example in my database i have around 4 lakhs records with logical database name 'A' and around 1 lakh of records with logical database name 'B'. The following code displays all B records but programs hangs after retrieving some A records.
I'm using PAGE_SIZE=8192, numBuffers=2048, and runnig in Fedora Core3.
DbEnv myEnv(0);
     myEnv.set_cachesize(0, PAGE_SIZE * numBuffers, 0);
     myEnv.set_data_dir("/home/raviov/new/database");
          try {
               myEnv.open("./", DB_CREATE | DB_INIT_MPOOL, 0);
          catch (DbException &e) {
               cerr << "Exception occurred: " << e.what() << endl;
               exit(1);
          db=new Db(&myEnv,0);
          db->set_pagesize(PAGE_SIZE);     
          db->set_bt_compare(compare_int);
     dbname=itoa(p);
     try
     db->open(NULL,
               "treedb.db",
               dbname,
               DB_BTREE,
               0,
               0);
     catch(DbException &e)
          cerr << "Failed to open DB object" << endl;
          exit(1);
     db->cursor(NULL,&cursorp,0);
     key=new Dbt();
     data=new Dbt();
     while(ret=(cursorp->get(key,data,DB_NEXT))==0)
          j=*((int*)key->get_data());
          q=(*((struct tuple*)data->get_data())).startPos;
          r=(*((struct tuple*)data->get_data())).endPos;
          s=(*((struct tuple*)data->get_data())).level;
          cout<<"position : "<<j<<"\t";
          cout<<"start : "<<q<<"\t";
          cout<<"end : "<<r<<"\t";
          cout<<"level : "<<s<<"\n";
     if(ret==DB_NOTFOUND)
          cout<<"no records";
          exit(1);
     if(cursorp!=NULL)
          cursorp->close();
     try
          db->close(0);
     catch(DbException &e)
          cerr << "Failed to close DB object" << endl;
          exit(1);
     myEnv.close(0);

Answer 1

HI Andrei,
thank you for giving reply, I'm not using any secondary indecies, subdatabases and not using any threads.
the following code displays index...
#include <stdio.h>
#include <db_cxx.h>
#include <iostream.h>
#include <db.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
int PAGE_SIZE=8192;
int numBuffers=2048;
char *itoa(const int x)
      char buf[100];
      snprintf(buf, sizeof(buf), "%d", x);
       return strdup(buf);
int compare_int(Db dbp, const Dbt a, const Dbt *b)
  int ai;
  int bi;
  memcpy(&ai,a->get_data(),sizeof(int));
  memcpy(&bi,b->get_data(),sizeof(int));
  return(ai-bi);
struct tuple
       int startPos;
       int endPos;
       int level;
main()
     FILE *fp;
     int i,j,k,l,m,n,total=0;
     char dbname[500],filename[500],str [500];
     tuple t;
     Db *db;
     Dbt key,data;
     DbEnv myEnv(0);
     myEnv.set_cachesize(0, PAGE_SIZE * numBuffers, 0);
     try {
            myEnv.open("/home/raviov/Desktop/example", DB_CREATE | DB_INIT_MPOOL, 0);
       catch (DbException &e) {
              cerr << "Exception occurred: " << e.what() << endl;
              exit(1);
     for(n=0;n<=84;n++)
          db = new Db(&myEnv, 0);     // Instantiate the Db object
                db->set_bt_compare(compare_int);
           db->set_pagesize(PAGE_SIZE);
          strcpy(filename,"/home/raviov/Desktop/GTCReport/code/sequence/splitter/tree/");
          strcat(filename,itoa(n));
          fp=fopen(filename,"r");
          if(fp==NULL)
               cout<<"error in opening the file";
               exit(0);
          while(fgets (str , 500 , fp)!=NULL)
               sscanf(str,"%d(%d,%d,%d,%d)",&i,&j,&k,&l,&m);
               key=new Dbt(&i,sizeof(int));
               if(total==0)
                    strcpy(dbname,itoa(j));
               t.startPos=k;
               t.endPos=l;
               t.level=m;
               data=new Dbt(&t,sizeof(t));     
               if(total==0)
                    try
                         db->open(NULL,
                         "tree.db",
                                   dbname,
                          DB_BTREE,
                            DB_CREATE,
                            0);
                    catch(DbException &e)
                           cerr << "Failed to create DB object" << endl;
                         exit(1);
                    total=99;
               int ret=db->put(NULL,key,data,DB_NOOVERWRITE);
               if(ret==DB_KEYEXIST)
                    cout<<"key already exist\n";
                    exit(1);
               delete key;
               delete data;
          total=0;
          fclose(fp);
          try
               db->close(0);
          catch(DbException &e)
                 cerr << "Failed to close DB object" << endl;
               exit(1);
     myEnv.close(0);
}The following code retrieves the records from database that we had built above...
#include <stdio.h>
#include <db_cxx.h>
#include <iostream.h>
#include <db.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
int PAGE_SIZE=8192;
int numBuffers=2048;
char *itoa(const int x)
      char buf[100];
      snprintf(buf, sizeof(buf), "%d", x);
       return strdup(buf);
int compare_int(Db dbp, const Dbt a, const Dbt *b)
  int ai;
  int bi;
  memcpy(&ai,a->get_data(),sizeof(int));
  memcpy(&bi,b->get_data(),sizeof(int));
  return(ai-bi);
struct tuple
       int startPos;
       int endPos;
       int level;
main()
     FILE *fp;
     int i,j,k,l,m,n,total=0;
     char *dbname;
     char filename[200],str [100];
     tuple t;
     Db *db;
     Dbt key,data;
     Dbc *cursorp=NULL;
     int ret,x=4;
     char *ravi;
     int p=84763;
     int y=2134872;
     int r,s,q,count=0;
     DbEnv myEnv(0);
     myEnv.set_cachesize(0, PAGE_SIZE * numBuffers, 0);
     myEnv.set_data_dir("/home/raviov/new/database");
          try {
                  myEnv.open("./", DB_CREATE | DB_INIT_MPOOL, 0);
           catch (DbException &e) {
                  cerr << "Exception occurred: " << e.what() << endl;
                  exit(1);
          db=new Db(&myEnv,0);
          db->set_pagesize(PAGE_SIZE);     
          db->set_bt_compare(compare_int);
     dbname=itoa(p);
     try
          db->open(NULL,
                "tree.db",
                 dbname,
                 DB_BTREE,
                 0,
                 0);
     catch(DbException &e)
            cerr << "Failed to open DB object" << endl;
          exit(1);
     db->cursor(NULL,&cursorp,0);
     key=new Dbt();
     data=new Dbt();
     while(ret=(cursorp->get(key,data,DB_NEXT))==0)
          j=*((int*)key->get_data());
          q=(*((struct tuple*)data->get_data())).startPos;
          r=(*((struct tuple*)data->get_data())).endPos;
          s=(*((struct tuple*)data->get_data())).level;
          cout<<"position   : "<<j<<"\t";
          cout<<"start : "<<q<<"\t";
          cout<<"end   : "<<r<<"\t";
          cout<<"level   : "<<s<<"\n";
          delete key;
          delete data;
     if(ret==DB_NOTFOUND)
          cout<<"no records";
          exit(1);
     if(cursorp!=NULL)
          cursorp->close();
     try
          db->close(0);
     catch(DbException &e)
            cerr << "Failed to close DB object" << endl;
          exit(1);
     myEnv.close(0);     
}