java - How to improve performance of Updating data using JPA -

i using ejb , container managed em ( local testing creating em here). have requirement need update database based on condition, issue update taking long time, how reduce ?

i tried 2 approach 1> update query 2> update in entity

please let me know if doing mistake, or other approach exist.

note : code update below

    public class test {     private static final int oaonaccount = 0;     private static final int arraylist = 0;     private static entitymanagerfactory emf;     private static entitymanager em;     static int test_size = 20000/4;      public static void main(string[] args) { //       createbulk();         createupdatequery(); //       update();      }      private static void createupdatequery() {         long st = system.currenttimemillis();         emf = persistence.createentitymanagerfactory("jpa");         em = emf.createentitymanager();         system.out.println("---- createupdatequery ---");         entitytransaction tx = em.gettransaction();         query query = em.createquery("select p oaonaccount p");         tx.begin();         java.util.vector<oaonaccount> list = (java.util.vector<oaonaccount>) query.getresultlist();         (int = 0; < list.size(); i++) {             string m = 1000000 + (i / 20) + "";             query = em                     .createquery("update oaonaccount p set p.status='completed', p.billingdoc='12112abcs' p.crdrindicator='h' , p.status ='open' , p.documentnumber="+ m);             query.executeupdate();         }          em.flush();         tx.commit();          long et = system.currenttimemillis();          system.out.println("test.createupdatequery() time " + (et - st));      }      private static void update() {          long st = system.currenttimemillis();         emf = persistence.createentitymanagerfactory("jpa");         em = emf.createentitymanager();         system.out.println("---- update ---");         entitytransaction tx = em.gettransaction();         query query = em.createquery("select p oaonaccount p");         tx.begin();          java.util.vector<oaonaccount> list = (java.util.vector<oaonaccount>) query                 .getresultlist();         (int = 0; < list.size(); i++) {             string m = 1000000 + (i / 20) + "";             query = em                     .createquery("select p oaonaccount p p.crdrindicator='h' , p.status ='open' , p.documentnumber="                             + m);             java.util.vector<oaonaccount> listen = (java.util.vector<oaonaccount>) query                     .getresultlist();             (int j = 0; j < listen.size(); j++) {                 listen.get(j).setbillingdoc("12112abcs");                 listen.get(j).setstatus("completed");             }         }          em.flush();         tx.commit();          long et = system.currenttimemillis();          system.out.println("test.update() time " + (et - st));      }      public static void createbulk() {         long st = system.currenttimemillis();         emf = persistence.createentitymanagerfactory("jpa");         em = emf.createentitymanager();         system.out.println("-------");         entitytransaction tx = em.gettransaction();         tx.begin();          (int = 0; < test_size; i++) {             oaonaccount entity = new oaonaccount();             entity.setid("id-" + i);             entity.setcrdrindicator(i % 2 == 0 ? "h" : "s");             entity.setdocumentnumber(1000000 + (i / 20) + "");             entity.setassignment(89000000 + (i / 27) + "");             entity.setstatus("open");             em.persist(entity);         }         em.flush();         tx.commit();          long et = system.currenttimemillis();          system.out.println("test.createbulk() time " + (et - st));      }  } 

you should execute em.flush() every n- number of iterations. example if n- low more number of db interactions hence slow in executing code . if n- high many objects resides in memory more swappings hence slow in executing code . please choose n value moderately , apply it. tried update 2.4 million records, faced same problem.

      (int = 0; < list.size(); i++) {         string m = 1000000 + (i / 20) + "";         query = em                 .createquery("update oaonaccount p set p.status='completed', p.billingdoc='12112abcs' p.crdrindicator='h' , p.status ='open' , p.documentnumber="+ m);         query.executeupdate();         if(i%100==0){// 100 show example-- % operation costly. can use better logic flush. frequent flushing necessary           em.flush();           }     }