java - Transaction Isolation Level -



java - Transaction Isolation Level -

i seek describe problem in jpa transaction isolation levels.

database structure:

table1 -> pk defined date ('ddmmyyyy') table2 -> fk table1

jpa( isolation level :: read_commited) - code:

query query = em.createquery("from table1 trd trd.id = :d"); query.setparameter("d", date); table1 t = null; try{ t = (table1) query.getsingleresult(); }catch(javax.persistence.noresultexception e){ t = null; } if(t==null){ t=new table1 (date); em.persist(trd); } for(table2 q:tables2){ q.settable1(t); em.merge(q); }

so procedure check if record exists in db , if not create new one. method corect if scheme in based on 1 thread. otherwise there possible situation this:

thread 1 : check if entity represent date exists in database thread 2 : same

both of them think such record has not exist yet, add together new one. ok until moment of commiting transactions. first 1 commited without exception, purchase sec 1 rising exception related primary key duplication.

is possibility preserve such situation except changing isolation level serializable?

yes, in general isolation level = serializable should solve problem. not underestimate side effects when changing isolation level stiff option. may influence database utilization request throughput. maybe can explicitly commit trx after creating t1, open trx: entitymanager.gettransaction().commit()

you still have grab duplicate key exception.

java database hibernate jpa transactions

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