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how to use pg_column_size in hibernate?

I am trying to get the size of a row in a postgresql table, I found that pg_column_size would do the trick, but its not working with hibernate :
#Query("SELECT pg_column_size(t.*) as filesize FROM TABLE as t where name=:name")
int getSize(#Param("name") String name);
intellij is giving this error :
< operator > or AS expected, got '('
I guess the problem is that hibernate doesnt support specific postgresql queries, it only supports the basic sql queries.
so is there a way around this ? if not is there a way to get/estimate the size of a postgresql row in java ?

In order to use a built-in postgres function , you have to declare you JPA query as nativeQuery
you should first change query to native (hibernate will directly execute the query instead of jpa -> sql generation )
#Query(value="SELECT pg_column_size(t.*) as filesize FROM TABLE as t where name=:name",nativeQuery=true)
int getSize(#Param("name") String name);
Also be sur of the TABLE name to be correct .

Add nativeQuery = true after the native query.
#Query("SELECT pg_column_size(t.*) as filesize FROM users as t where t.name=:name",nativeQuery = true)
use above Query, Hope This will work.

Convert Postgresql query to Hibernate

In my Java Web application I use Postgresql and some data tables are filled automatically in server. In the database I have a STATUS table like below:
I want to select the data related to a vehicle between selected dates and where the vehicle stayed connected. Simply I want to select the data which are green in the above table which means I exactly want the data when firstly io1=true and the data when io1=false after the last io1=true. I have postgresql query statement which exactly gives me the desired data; however, I have to convert it to HQL because of my application logic.
working postgresql query:
WITH cte AS
( SELECT iostatusid, mtstrackid, io1,io2,io3, gpsdate,
(io1 <> LAG(io1) OVER (PARTITION BY mtstrackid
ORDER BY gpsdate)
) AS status_changed
FROM iostatus
WHERE mtstrackid = 'redcar' AND gpsdate between '2014-02-28 00:00:00' and '2014-02-28 23:59:59'
)
SELECT iostatusId, mtstrackid, io1, io2, io3,gpsdate
FROM cte
WHERE status_changed
OR io1 AND status_changed IS NULL
ORDER BY gpsdate ;
How should I convert the above query to HQL or how could I retrieve the desired data with HQL?

The goal of hibernate is mapping database entities to java objects. This kind of complex queries are not entities themselves. This is against the spirit of hibernate.
If this query generates an entity in your application logic, I recommend putting the results into a table and applying Hibernate queries to that table.
If this query generates some kind of aggregation or summary, there are two possible ways:
One way is you compute this aggregation/summary in your application after retrieving entities from iostatus table with hibernate.
If this query has nothing to do with your application logic then you can use Native SQL interface of Hibernate and execute the query directly. (You can even use JPA if you are willing to manipulate two database connections.)
If you absolutely need to convert it to HQL, you need to eliminate the partition function. If the order of iostatusId is identical to the order of gpsdate, you can do it similar to
SELECT i2.*
FROM iostatus i1
INNER JOIN iostatus i2 ON i1.iostatusId = i2.iostatusId - 1
AND i1.io1 <> i2.io1
AND i1.mstrackid = i2.mstrackid
WHERE i2.mtstrackid = 'redcar' AND
i2.gpsdate between '2014-02-28 00:00:00' and '2014-02-28 23:59:59'
If gpsdate is no way related to iostatusId then you need something like
SELECT i2.*
FROM iostatus i1
INNER JOIN iostatus i2 ON i1.gpsdate < i2.gpsdate
AND i1.io1 <> i2.io1
AND i1.mstrackid = i2.mstrackid
WHERE i2.mtstrackid = 'redcar' AND
i2.gpsdate between '2014-02-28 00:00:00' and '2014-02-28 23:59:59' AND
NOT EXISTS (SELECT * FROM iostatus i3
WHERE i3.gpsdate > i1.gpsdate AND
i2.gpsdate > i3.gpsdate AND
i3.io1 = i1.io1 AND
i1.mstrackid = i3.mstrackid)
I guess both of the queries can be converted to HQL, but I'm not positively sure.
By the way I must warn you that, these methods might not perform better then finding the changes in your application, because they involve joining the table onto itself, which is an expensive operation; and the second query involves a nested query after the join, which is also quite expensive.

Order by, group by, first result in HQL (convert from Oracle SQL)

How would represent the following Oracle SQL in Hibernate HQL.
select table_num
, room_id
, min(event_type) keep(dense_rank first order by changed_on desc)
from room_history
group by table_num, room_id;
The idea behind the query is to order the table "room_history" by "changed_on" datetime column and then group it by "table_num" and "room_id" pairs whilest keeping the first "event_type" for each group. The mentioned query works for Oracle but I have trouble converting it into HQL.
Purpose is to get the latest "event_type" for "table_num" and "room_id" pair.

It seems this is not achievable
I ended up converting the following SQL query instead. It is not perfect but it does the job for my purposes.
select table_num, event_type et from room_history where id in (select max(id) from privacy_history group by msisdn);
I was able to do this assumptions since when for this table always a.id > b.id then also a.changed_on> b.changed_on.

jpa select statement with subnets

I am trying to write query with multiple select subnets in it.But I defined a nativequery
I am giving error. Compiler specifies that "(" after "from" is not proper. How can I define
a native query in JPA 2.0
For eaxmple:
SELECT *
from (SELECT ****C) REI3 where column1 != 1
GROUP BY REI3.column2 order by REI3.column3 ASC

JPA does not have too much to do with validating SQL syntax, query is passed to JDBC driver. Likely you are trying run query such a way, that it is interpreted as JP QL. Instead try following method to execute it as
Query q = em.createNativeQuery("Your SQL here");
Other alternative is to use NamedNativeQuery Example

How to construct advanced Hibernate Query with OR and summarize functions

I have a rather complex query which works in SQL, but I would like to express this in HQL for portability. I'm going to fetch a user configured preference value if they exist, if not I must use a default value. This value must be subtracted from current date and the matched against a column in the table which I'm interested in:
select d.id, d.guid, d.deletetimestamp, u.id
from descriptor d, ownerkey ow, user u
where
d.parentid in
(select td.id
from descriptor td, store s
where s.type = 'Trash'
and s.descriptorid = td.id
)
and d.ownerkeyid = ow.id
and ow.ownerid = u.id
and
(
(d.deletetimestamp < CURRENT_TIMESTAMP() - INTERVAL
(select pv.value
from preferencevalue pv, userpreference up
where u.id = up.userid
and up.preferenceid = 26
and up.value = pv.id)
DAY)
or
(d.deletetimestamp < CURRENT_TIMESTAMP() - INTERVAL
(select cast(pv.value as SIGNED)
from preferencevalue pv, defaultpreference dp
where dp.preferenceid = 26
and not exists(select up.userid from userpreference up where u.id = up.userid and up.preferenceid = 26)
and dp.value = pv.id)
DAY)
)
I'm trying to construct this by using the Criteria API which seems to include most of the logical operators that I need (equals, larger than, or, isEmpty/isNull), but not sure how I would express all these parts.
Using a view is not an option at this point since we're using MySQL as the production database while the integration tests are running with H2 inmemory database. I'm not able to get find the sata substract function in H2 while MySQL do support this.
The select fields isn't important since they have only been used for testing purposes.

you can use Restrictions.disjunction() for or -and Restrictions.conjuction() for and clauses.
To reference a certain property of an entity (like pv.value) you can use Projections.property("value")
for the casting I'm not sure, perhaps using the #Formula annotation on your entity? But this is a hibernate and not a JPA annotation.
as far as I know there is no equivalent for INTERVAL in hibernate but in such cases (maybe also for the above cast) you could use Restrictions.sqlRestriction("some sql...")
It will be a challenge putting all of this together to transform your query to hibernate criteria.
greetz,
Stijn