Cursor skip entry during iteration

[billon-pl]

This is issue is identical to issue-106 from https://github.com/cruppstahl/upscaledb
See cruppstahl/upscaledb#106

Please consider following sample:

int main()
{
    ups_env_t* env;
    ups_env_create(&env, "test.db", UPS_ENABLE_TRANSACTIONS, 0664, 0); // required to reproduce
    //ups_env_create(&env, "test.db", 0, 0664, 0);

    ups_parameter_t params[] = {
    {UPS_PARAM_KEY_TYPE, UPS_TYPE_UINT32},
    {0, }
    };

    ups_db_t* db;
    ups_env_create_db(env, &db, 1, 0, &params[0]);

    int item_count = 57;

    for (int i = 0; i < item_count; i++)
    {
        ups_key_t key = ups_make_key(&i, sizeof(i));
        ups_record_t record = {0};

        ups_db_insert(db, 0, &key, &record, 0);
    }

    ups_cursor_t* cur;

    ups_cursor_create(&cur, db, 0, 0);

    int key_data = 0;
    ups_key_t key = {0}; key.data = &key_data; key.size = sizeof(key_data);
    ups_record_t rec = {0};

    auto st = ups_cursor_find(cur, &key, &rec, UPS_FIND_GEQ_MATCH); // required to reproduce

    int counter = 0;
    do{
        ups_cursor_move(cur, &key, &rec, 0); // required to reproduce
        if(counter != *reinterpret_cast<int*>(key.data)){
            std::cout << "Invalid entry: " << counter << std::endl;
        }
        counter++;
    }while(UPS_SUCCESS == ups_cursor_move(cur, &key, &rec, UPS_CURSOR_NEXT));

    ups_cursor_close(cur);

    ups_db_close(db, 0);

    return 0;
}

What is printed to the output:

    Invalid entry: 51 Should be:50
    Invalid entry: 52 Should be:51
    Invalid entry: 53 Should be:52
    Invalid entry: 54 Should be:53
    Invalid entry: 55 Should be:54
    Invalid entry: 56 Should be:55

50th entry is skipped by the cursor during iteration.

In this case ups_cursor_move(cur, &key, &rec, 0) was inserted to simulate situation when there is a possibility for invalidation of key/rec values by subsequent ups api calls, so just before reading them I want to update their values according to cursor position. (I actually experience this scenario in my app).

Since ups_cursor_find(cur, &key, &rec, UPS_FIND_GEQ_MATCH) is also required is this issue connected to 105 ?

[billon-pl]

• This case is added to test suite of the project.

• The source code can be found in file issue106.cc

• There is work around for this issue: do not use ups_cursor_move(cur, &key, &rec, 0)