Bulk read problems: DB_MULTIPLE/DB_MULTIPLE_KEY buffers must be aligned

Question

Hi I am trying to bulk read a Btree database that has the following stats...
53162 Btree magic number
9 Btree version number
Little-endian Byte order
duplicates Flags
2 Minimum keys per-page
4096 Underlying database page size
1007 Overflow key/data size
5 Number of levels in the tree
16M Number of unique keys in the tree (16063325)
25M Number of data items in the tree (25429676)
13177 Number of tree internal pages
23M Number of bytes free in tree internal pages (56% ff)
788089 Number of tree leaf pages
1881M Number of bytes free in tree leaf pages (41% ff)
465 Number of tree duplicate pages
1003680 Number of bytes free in tree duplicate pages (47% ff)
0 Number of tree overflow pages
0 Number of bytes free in tree overflow pages (0% ff)
0 Number of empty pages
0 Number of pages on the free list
I have the following code...
     int bsize = 4096*1024;
     char *buffer = new char[bsize];
     Dbt datax(buffer, bsize);
     datax.set_flags(DB_DBT_USERMEM);
     ret = cursorp->get(&key, &datax, DB_SET_RANGE | DB_MULTIPLE_KEY);
However, I keep getting an error saying...
DB_MULTIPLE/DB_MULTIPLE_KEY buffers must be aligned, at least page size and multiples of 1KB
terminate called after throwing an instance of 'DbException'
what(): Dbc::get: Invalid argument
Any insight is appreciated.
thanks
Nishant

Answer 1

HI Michael, I changed as per your suggestion and it works now.. however the bulk read is giving worse performance than reading one at a time.
     int bsize = 4*4096*1024;     //64MB
     char *buffer = new char[bsize];
     Dbt datax(buffer, bsize);
     datax.set_ulen(bsize);
     datax.set_flags(DB_DBT_USERMEM);
     ret = cursorp->get(&key, &datax, DB_SET_RANGE | DB_MULTIPLE_KEY);
     if (ret != 0) {
          cout << "Could not find any trades data for " << bsid << endl;
     } else {
               do {
                    DbMultipleKeyDataIterator BulkIterator(datax);
                    while (BulkIterator.next(key, data)) {
                    clBidAskTrade d = (clBidAskTrade )data.get_data();
                         print_trade((char *)key.get_data(), d, "trades", format);
                    if (cursorp->get(&key, &datax, DB_NEXT | DB_MULTIPLE_KEY) == DB_NOTFOUND) {
                         break;
               } while (1);
     delete buffer;
is running slower than...
          ret = cursorp->get(&key, &data, DB_SET_RANGE);
          if (ret != 0) {
               cout << "Could not find any trades data for " << bsid << endl;
          } else {
               clBidAskTrade d = (clBidAskTrade )data.get_data();
                    while ((ret = cursorp->get(&key, &data, cur_flag)) == 0)) {
                         d = (clBidAskTrade *)data.get_data();
                         print_trade((char *)key.get_data(), d, "trades", format);
what am I doing wrong? thanks for your help.