Hash Aggregate Python SequenceIterator Methods

Hash Aggregate methods take various input arguments and return two iterators: one for the grouping values and one for the group aggregates.

hash_agg_max( ... )	Returns a sequence of the same type with the maximum value for each group of elements
hash_agg_min( ... )	Returns a sequence of the same type with the minimum value for each group of elements
hash_agg_sum( ... )	Returns a sequence of the same type with the sum of each group of elements
hash_agg_avg( ... )	Returns a double result sequence with the average of each group of elements
hash_agg_approxdc( ... )	Returns a uint4 result sequence with the approximate district count for each group of elements
hash_agg_count( ... )	Returns a uint8 result_count sequence with the count of the number of elements in each group
hash_agg_distinct_count( ... )	Returns a uint8 result_count sequence with the count of the number of distinct elements in each group
hash_agg_dup_count()	Returns a uint8 sequence with the count of duplicates in each group. Parameter min_occurrences specifies minimal number for occurrences of a particular value to be counted. With min_occurrences=1 this function is equivalent to mco_seq_hash_agg_distinct_count(), with min_occurrences=2 it counts items encountered more than once... If n_pairs parameter is 0, then mco_seq_hash_init_size is used to specify size of hash table and it is automatically extended when threshold determined by mco_seq_hash_load_factor is reached.

Example

Following is an example code snippet demonstrating how to use a hash aggregate function to calculate the average Close price for Volume values in ranges of 0..9, 10..19, 20..29, etc.:

    {
        mco_trans_h trans;
        mco_cursor_t quote_cursor;
        Quote quote;
        mco_seq_iterator_t close_iterator, volume_div_10_iterator; 
        mco_seq_iterator_t group_iterator,  avg_iterator;
        MCO_RET rc;
        ...
         
        for (rc = mco_cursor_first(trans, &quote_cursor); 
            rc != MCO_S_CURSOR_END; 
            rc = mco_cursor_next(trans, &quote_cursor)) 
        {
            Quote_from_cursor(trans, &quote_cursor, &quote);
            Quote_close_iterator(&quote, &close_iterator);
            Quote_volume_iterator(&quote, &volume_iterator);
             
            rc = mco_seq_const_uint4(&const_iterator, 10));
            rc = mco_seq_div_uint4(&volume_div_10_iterator, &volume_iterator, &const_iterator);
             
             
            rc = mco_seq_hash_agg_avg_float(&avg_iterator, &group_iterator, 
            
                    &close_iterator, &volume_div_10_iterator, 0);
            
            ...
            mco_seq_free_hash(&avg_iterator);
        }
        ...
    }