I have 2 tables Project_Products(id, product_id, version, name) and Cos_Product(cos_id, version, description)
Now I need to join the tables on Project_Products.product_id = Cos_Product.cos_id and create a column isConflict whose value is going to be 0 or 1 based on if Project_Products.version = Cos_Product.version
Currently I'm running it by using native query using Hibernate Entity Manager. This works perfectly fine by using the query
Select p.id, p.project_id, p.name,
case when p.version = c.version then 0 else 1 as is_conflict
from Project_Products p left join Cos_Product c on p.product_id = c.cos_id
Now how to do this scenario using spring jpa? Without using native query.
Related
I have 2 different entities. table1 has a column which is primary key of table2.
both of the tables has respected repository.
If I write below query in one of the repository it gives error
QuerySyntaxException: unexpected token:
#Query("select new stats.UserCountDTO(b.objectiveId, count(b.objectiveId), a.locationCountry)"+
" from UserIdentityEntity a, UserObjectiveEntity b where b.userIdentityId == a.id and b.cId = ?1")
How can I write join queries in this case using spring data jpa?
You just make a mistake. The
b.userIdentityId == a.id
should be:
b.userIdentityId = a.id
I have a query written using Predicates in Hibernate and I need to add a subquery on a join table to count the number of joins and order by the number of joins where they exist in an array of ids.
The join table is a ManyToMany relation.
I am using flyway to setup the table schema, so while the join table exists in the database, a join model is not needed in Hibernate to join the 2 related models therefore no join model exists.
I don't care about retrieving these related models, I just want the number of joins so that I can order by them.
The following is PostGreSQL, which works. I need to convert the following PSQL into a Predicate based query:
SELECT u.*, COUNT(jui.interest_id) AS juiCount
FROM "user" u
LEFT JOIN (
SELECT ui.user_id, ui.interest_id
FROM user_interest ui
WHERE ui.interest_id IN (?)
) AS jui ON u.id = jui.user_id
GROUP BY u.id
ORDER BY juiCount DESC
Where the ids provided for the IN condition are passed into the subquery. The above query is in PostGreSQL.
Working with what I have so far:
CriteriaBuilder b = em.getCriteriaBuilder();
CriteriaQuery<User> q = b.createQuery(User.class);
Root<User> u = q.from(User.class);
// This doesn't make sense because this is not a join table
// Subquery<Interest> sq = q.subquery(Interest.class)
// Root<Interest> squi = sq.from(Interest.class);
// sq.select(squi);
// sq.where(b.in("interest_id", new LiteralExpression<Long[]>((CriteriaBuilderImpl) b, interestIds)));
q.orderBy(
// b.desc(b.tuple(u, b.count(squi))),
b.asc(u.get(User_.id))
);
q.where(p);
return em
.createQuery(q)
.getResultList();
Everything I have managed to find doesn't quite seem to fit right given that they are not using ManyToMany in the use of q.subquery() in their example.
Anyone can help fill in the blanks on this please?
I have set of tables in my data base like table A which has set of set of categories , table B set of repositeries. A and B are related by categoryid. And then table C which has set of properties for a repoId. Table C and A are associated with repoId.
Table C can have multiple values for a repoId.
The data in C table is like a property say a number string like 12345XXXX (max data of 10 characters) and I have to find the top 6 matching characters of a particular value in table C and the count of repoIds associated with those top 6 value for a particular data in table A (categoryid).
Table A(set of categories ) ---------> Table B (set of repositories, associated with A with categoryid)---------> Table V (set of FMProperties against a repoId)
Now currently, this has been achieved by using joins and substring queries on these tables and it is very slow.
I have to achieve this functionality using Elastic search. I dont have clear view how to start?
Do I create separate documents / indexes for table A , B and C or fetch the info using sql query and create a single document.
And how we can apply this analytics part explained above.
I am very new and amateur in this technology but I am following the tutorials provided at elasticsearch site.
PFB the query in mysql for this logic:-
select 'fms' as fmstype, C.fmscode as fmsCode,
count(C.repoId) as countOffms from tableC C, tableB B
where B.repoId = C.repoId and B.categoryid = 175
group by C.fmscode
order by countOffms desc
limit 1)
UNION ALL
(select 'fms6' as fmstype, t1.fmscode, t2.countOffms from tableC t1
inner join
(
select substring(C.fmscode,1,6) as first6,
count(C.repoId) as countOffms from tableC C, tableB B
where B.repoId = C.repoId and B.categoryid = 175 and length(C.fmscode) = 6
group by substring(C.fmscode,1,6) order by countOffms desc
limit 1 ) t2
ON
substring(t1.fmscode,1,6) = t2.first6 and length(t1.fmscode) = 6
group by t1.fmscode
order by count(t1.fmscode) desc
limit 1)
I have two classes: Property and PropertyValue. A property has several values where each value is a new revision.
When retrieving a set of properties I want to include the latest revision of the value for each property.
in T-SQL this can very efficiently be done like this:
SELECT
p.Id,
pv1.StringValue,
pv1.Revision
FROM dbo.PropertyValues pv1
LEFT JOIN dbo.PropertyValues pv2 ON pv1.Property_Id = pv2.Property_Id AND pv1.Revision < pv2.Revision
JOIN dbo.Properties p ON p.Id = pv1.Property_Id
WHERE pv2.Id IS NULL
ORDER BY p.Id
The "magic" in this query is to join on the lesser than condition and look for rows without a result forced by the LEFT JOIN.
How can I accomplish something similar using LINQ to EF?
The best thing I could come up with was:
from pv in context.PropertyValues
group pv by pv.Property into g
select g.OrderByDescending(p => p.Revision).FirstOrDefault()
It does produce the correct result but is about 10 times slower than the other.
Maybe this can help. Where db is the database context:
(
from pv1 in db.PropertyValues
from pv2 in db.PropertyValues.Where(a=>a.Property_Id==pv1.Property_Id && pv1.Revision<pv2.Revision).DefaultIfEmpty()
join p in db.Properties
on pv1.Property_Id equals p.Id
where pv2.Id==null
orderby p.Id
select new
{
p.Id,
pv1.StringValue,
pv1.Revision
}
);
Next to optimizing a query in Linq To Entities, you also have to be aware of the work it takes for the Entity Framework to translate your query to SQL and then map the results back to your objects.
Comparing a Linq To Entities query directly to a SQL query will always result in lower performance because the Entity Framework does a lot more work for you.
So it's also important to look at optimizing the steps the Entity Framework takes.
Things that could help:
Precompile your query
Pre-generate views
Decide for yourself when to open the database connection
Disable tracking (if appropriate)
Here you can find some documentation with performance strategies.
if you want to use multiple conditions (less than expression) in join you can do this like
from pv1 in db.PropertyValues
join pv2 in db.PropertyValues on new{pv1.Property_ID, Condition = pv1.Revision < pv2.Revision} equals new {pv2.Property_ID , Condition = true} into temp
from t in temp.DefaultIfEmpty()
join p in db.Properties
on pv1.Property_Id equals p.Id
where t.Id==null
orderby p.Id
select new
{
p.Id,
pv1.StringValue,
pv1.Revision
}
I have the following Linq statement:
(from order in Orders.AsEnumerable()
join component in Components.AsEnumerable()
on order.ORDER_ID equals component.ORDER_ID
join detail in Detailss.AsEnumerable()
on component.RESULT_ID equals detail.RESULT_ID
where orderRestrict.ORDER_MNEMONIC == "MyOrderText"
select new
{
Mnemonic = detail.TEST_MNEMONIC,
OrderID = component.ORDER_ID,
SeqNumber = component.SEQ_NUM
}).ToList()
I expect this to put out the following query:
select *
from Orders ord (NoLock)
join Component comp (NoLock)
on ord .ORDER_ID = comp.ORDER_ID
join Details detail (NoLock)
on comp.RESULT_TEST_NUM = detail .RESULT_TEST_NUM
where res.ORDER_MNEMONIC = 'MyOrderText'
but instead I get 3 seperate queries that select all rows from the tables. I am guessing that Linq is then filtering the values because I do get the correct values in the end.
The problem is that it takes WAY WAY too long because it is pulling down all the rows from all three tables.
Any ideas how I can fix that?
Remove the .AsEnumerable()s from the query as these are preventing the entire query being evaluated on the server.