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dicero
 Post subject: insert and select of the same data in the same session
PostPosted: Mon Jan 28, 2013 2:06 pm 
Newbie

Joined: Mon Jan 28, 2013 1:54 pm
Posts: 2
Hi,
i have a problem. if I run this code:

Code:
public void insertContext(final int time, final int day, final String weather, final String events) {
       this.getHibernateTemplate().execute(
            new HibernateCallback() {
               public Object doInHibernate(Session session)
                     throws PersistenceException {
                  session.flush();
               
                  String sqlString = new StringBuffer("insert into context (time_slot, day, weather,events) values (").append(time).append(",").append(day).append(",'").append(weather).append("','").append(events).append("');").toString();
                                 
                          System.out.println(sqlString);

                  Query qry = session.createSQLQuery(sqlString);
                  qry.executeUpdate();
               
                  return null;


and then execute this code:

Code:
public boolean existContext(final int time, final int day) {
      return (boolean) this.getHibernateTemplate().execute(
            new HibernateCallback() {

               public Object doInHibernate(Session session)
                     throws PersistenceException {

                  session.flush();
                  String sqlString = new StringBuffer("select count(*) from context where time_slot=").append(time).append(" and day=").append(day).append(";").toString();
                  System.out.println(sqlString);

                  Query qry = session.createSQLQuery(sqlString).addScalar("count", Hibernate.INTEGER);
                  qry.setCacheable(true);
                  List result = (List)qry.setResultTransformer(Transformers.TO_LIST).list().get(0);
                  int count = (Integer)result.get(0);
                  System.out.println(count+"<------------------------count");
                  if (count==0) {
                  ...


if everything is performed in the same run (JAVA) and in the same session, the data entered by the first query is not found in the second query. why?


Last edited by dicero on Thu Jan 31, 2013 9:36 am, edited 1 time in total.

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pb00067
 Post subject: Re: insert and select of the same data in the same session
PostPosted: Thu Jan 31, 2013 4:58 am 
Expert
Expert

Joined: Tue Jun 16, 2009 3:36 am
Posts: 990
Are you sure that both operations (insert-query, select-query) are acting within the same session?
Eventually I suggest you to log all jdbc-activities with a JDBC-Logger like p6spy, so you can effectively check if it happens is different sessions (transactions) or not.
If it happens in different sessions, then the select-query might not see the inserted records because of Isolation-settings (READ_COMMITED or higher) due to the fact that the inserted data isn't commited yet.
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dicero
 Post subject: Re: insert and select of the same data in the same session
PostPosted: Thu Jan 31, 2013 8:05 am 
Newbie

Joined: Mon Jan 28, 2013 1:54 pm
Posts: 2
pb00067 wrote:
Are you sure that both operations (insert-query, select-query) are acting within the same session?
Eventually I suggest you to log all jdbc-activities with a JDBC-Logger like p6spy, so you can effectively check if it happens is different sessions (transactions) or not.
If it happens in different sessions, then the select-query might not see the inserted records because of Isolation-settings (READ_COMMITED or higher) due to the fact that the inserted data isn't commited yet.


thanks for the reply. I installed p6spy and gave me back the log file. But how do I know if it uses the same session?
these are the strings of my interest:
Code:
1359633434916|2|1|statement|select count(*) from context where time_slot=34 and day=0;|select count(*) from context where time_slot=34 and day=0;
1359633434916|-1||resultset|select count(*) from context where time_slot=34 and day=0;|count = 0
1359633434922|3|2|statement|insert into context (time_slot, day, weather,events) values (34,0,'sunny','nothing') returning id;|insert into context (time_slot, day, weather,events) values (34,0,'sunny','nothing') returning id;
1359633434922|-1||resultset|insert into context (time_slot, day, weather,events) values (34,0,'sunny','nothing') returning id;|
1359633434950|26|3|statement|insert into context (time_slot, day, weather,events) values (34,0,'sunny','nothing') returning id;|insert into context (time_slot, day, weather,events) values (34,0,'sunny','nothing') returning id;
1359633434951|-1||resultset|insert into context (time_slot, day, weather,events) values (34,0,'sunny','nothing') returning id;|
1359633434955|2|1|statement|insert into context (time_slot, day, weather,events) values (34,0,'sunny','nothing') returning id;|insert into context (time_slot, day, weather,events) values (34,0,'sunny','nothing') returning id;
1359633434956|-1||resultset|insert into context (time_slot, day, weather,events) values (34,0,'sunny','nothing') returning id;|

As you can see the insert of the same context is executed multiple times.
In practice, before I do the insert I check if the entry is already present with the "count" and if "count == 0" proceed with the insert but if i do all this in the same run java the count is always ==0.

PS: i have found a solution. If I set this string <property name="hibernate.cache.use_query_cache">true</property> to false in the hibernate configuration the problem is solved but the execution time increases considerably. Can I disable the cache only for a specific query?
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pb00067
 Post subject: Re: insert and select of the same data in the same session
PostPosted: Mon Feb 04, 2013 3:09 am 
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Expert

Joined: Tue Jun 16, 2009 3:36 am
Posts: 990
Quote:
But how do I know if it uses the same session?


The third parameter in the p6spy-log-line shows the session-id.
Looking at your p6-spy output, we can see that 3 different sessions (1,2,3) are used to do the operations.
Instead to disable the query-cache. I would try to get all working with one unique session.
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