IntHashMap key is int64, value is an uint64 (start from 1) before you use the IntHashMap, the user should make sure that sum of vectors' length equal to 8.

JoinMap is used for join.

StrHashMap key is []byte, value is an uint64 value (starting from 1) each time a new key is inserted, the hashtable returns a last-value+1 or, if the old key is inserted, the value corresponding to that key.

HashMap is the encapsulated hash table interface exposed to the outside.

Iterator allows users to do insert or find operations on hash tables in bulk.