Explanation of small Redis snippet -

i'm referring great answer given @sripathi krishnan question asked here on so: redis cache

i'm trying learn how use redis , research brought me question on so.

can please explain reason these 2 lines in code because i'm still finding difficult understand usefulness in code sripathi gave in answer.

$ hincrby unique_ids question 1 $ hincrby unique_ids answer 1 

i know creates hash 'unique_ids' key fields 'question' , 'answer' first initialised 0 increased 1. apart this, don't see link of unique_ids key flow i'm not sure if noob mind missing something.

these commands way generate synthetic primary keys.

in sri's example, people can add questions , answers in system. these entities need referenced, need identified unique keys. may imagine using kind of uuid mechanism this, using numeric keys simpler.

the unique_ids convenient container store next available keys of objects stored in system. add new question, increment question field of unique_ids (atomic operation redis) , use returned value key of new question. guarantees new questions have different key value.

in relational data stores, such feature provided sequences (oracle, postgresql) or autoincrement primary keys (mysql).