I am using queryDsl-Sql I need to do an update statement with a join clause like:
update MY_TABLE t1 set t1.MY_FIELD = 'SOME_VALUE'
JOIN MY_TABLE_2 t2 ON t1.FIELD_WITH_FK = t2.ID
where t2.OTHER_FIELD=12324556789 AND t2.OTHER_FIELD like '%something%'
Unfortunately, on queryDsl I was only able to do subqueries during update but not joins:
dsl.update(table1)
.set(my_field, "SOME_VALUE")
.where(
field_with_fk.in(
dsl.select(id).from(table2).where(other_field.eq(12324556789))
, fieldName.like("%something%"));
Which is translated to a subquery (as expected) and happens to take much much more time (difference between 10 seconds using joins and more than 1h using subselects)
I have seen that on JPAUpdateClause is possible to do so but I am not using QueryDsl-jpa here. QueryDSL-SQL has only SqlUpdateClause and I was not able to find how to join different tables when using It.
I think this is more a workaround than a solution, but maybe helps
also others:
dsl.update(table1)
.set(field1, myValue)
.addFlag(
QueryFlag.Position.START_OVERRIDE, //it replaces update by update with join
Expressions.stringTemplate("update {0} join {1} on {2} = {3} #", // I need # to ignore table1 otherwise incorrect SQL
table1, table2, table1FieldWithFkToTable2, table2Id))
.where(other_field.eq(12324556789), fieldName.like("%something%"));
this generates the following SQL:
update table1 join table2 on table1FieldWithFkToTable2 = table2Id #table1
set field1 = myValue
where other_field=12324556789 and fieldName like '%something%'
Related
What alternatives do I have to implement a union query using hibernate? I know hibernate does not support union queries at the moment, right now the only way I see to make a union is to use a view table.
The other option is to use plain jdbc, but this way I would loose all my example/criteria queries goodies, as well as the hibernate mapping validation that hibernate performs against the tables/columns.
You could use id in (select id from ...) or id in (select id from ...)
e.g. instead of non-working
from Person p where p.name="Joe"
union
from Person p join p.children c where c.name="Joe"
you could do
from Person p
where p.id in (select p1.id from Person p1 where p1.name="Joe")
or p.id in (select p2.id from Person p2 join p2.children c where c.name="Joe");
At least using MySQL, you will run into performance problems with it later, though. It's sometimes easier to do a poor man's join on two queries instead:
// use set for uniqueness
Set<Person> people = new HashSet<Person>((List<Person>) query1.list());
people.addAll((List<Person>) query2.list());
return new ArrayList<Person>(people);
It's often better to do two simple queries than one complex one.
EDIT:
to give an example, here is the EXPLAIN output of the resulting MySQL query from the subselect solution:
mysql> explain
select p.* from PERSON p
where p.id in (select p1.id from PERSON p1 where p1.name = "Joe")
or p.id in (select p2.id from PERSON p2
join CHILDREN c on p2.id = c.parent where c.name="Joe") \G
*************************** 1. row ***************************
id: 1
select_type: PRIMARY
table: a
type: ALL
possible_keys: NULL
key: NULL
key_len: NULL
ref: NULL
rows: 247554
Extra: Using where
*************************** 2. row ***************************
id: 3
select_type: DEPENDENT SUBQUERY
table: NULL
type: NULL
possible_keys: NULL
key: NULL
key_len: NULL
ref: NULL
rows: NULL
Extra: Impossible WHERE noticed after reading const tables
*************************** 3. row ***************************
id: 2
select_type: DEPENDENT SUBQUERY
table: a1
type: unique_subquery
possible_keys: PRIMARY,name,sortname
key: PRIMARY
key_len: 4
ref: func
rows: 1
Extra: Using where
3 rows in set (0.00 sec)
Most importantly, 1. row doesn't use any index and considers 200k+ rows. Bad! Execution of this query took 0.7s wheres both subqueries are in the milliseconds.
Use VIEW. The same classes can be mapped to different tables/views using entity name, so you won't even have much of a duplication. Being there, done that, works OK.
Plain JDBC has another hidden problem: it's unaware of Hibernate session cache, so if something got cached till the end of the transaction and not flushed from Hibernate session, JDBC query won't find it. Could be very puzzling sometimes.
I have to agree with Vladimir. I too looked into using UNION in HQL and couldn't find a way around it. The odd thing was that I could find (in the Hibernate FAQ) that UNION is unsupported, bug reports pertaining to UNION marked 'fixed', newsgroups of people saying that the statements would be truncated at UNION, and other newsgroups of people reporting it works fine...
After a day of mucking with it, I ended up porting my HQL back to plain SQL, but doing it in a View in the database would be a good option. In my case, parts of the query were dynamically generated, so I had to build the SQL in the code instead.
I have a solution for one critical scenario (for which I struggled a lot )with union in HQL .
e.g. Instead of not working :-
select i , j from A a , (select i , j from B union select i , j from C) d where a.i = d.i
OR
select i , j from A a JOIN (select i , j from B union select i , j from C) d on a.i = d.i
YOU could do in Hibernate HQL ->
Query q1 =session.createQuery(select i , j from A a JOIN B b on a.i = b.i)
List l1 = q1.list();
Query q2 = session.createQuery(select i , j from A a JOIN C b on a.i = b.i)
List l2 = q2.list();
then u can add both list ->
l1.addAll(l2);
A view is a better approach but since hql typically returns a List or Set... you can do list_1.addAll(list_2). Totally sucks compared to a union but should work.
Perhaps I had a more straight-forward problem to solve. My 'for instance' was in JPA with Hibernate as the JPA provider.
I split the three selects (two in a second case) into multiple select and combined the collections returned myself, effectively replacing a 'union all'.
Hibernate 6 added support for UNION.
So, you can now use UNION in JPQL queries like this:
List<String> topics = entityManager.createQuery("""
select c.name as name
from Category c
union
select t.name as name
from Tag t
""", String.class)
.getResultList();
And you can also also use UNION ALL if there are no duplicates to be removed:
List<String> topics = entityManager.createQuery("""
select c.name as name
from Category c
union all
select t.name as name
from Tag t
""", String.class)
.getResultList();
Besides UNION, you can also use EXCEPT and INTERSECT.
I too have been through this pain - if the query is dynamically generated (e.g. Hibernate Criteria) then I couldn't find a practical way to do it.
The good news for me was that I was only investigating union to solve a performance problem when using an 'or' in an Oracle database.
The solution Patrick posted (combining the results programmatically using a set) while ugly (especially since I wanted to do results paging as well) was adequate for me.
Here is a special case, but might inspire you to create your own work around. The goal here is to count the total number of records from two different tables where records meet a particular criteria. I believe this technique will work for any case where you need to aggregate data from across multiple tables/sources.
I have some special intermediate classes setup, so the code which calls the named query is short and sweet, but you can use whatever method you normally use in conjunction with named queries to execute your query.
QueryParms parms=new QueryParms();
parms.put("PROCDATE",PROCDATE);
Long pixelAll = ((SourceCount)Fetch.row("PIXEL_ALL",parms,logger)).getCOUNT();
As you can see here, the named query begins to look an aweful lot like a union statement:
#Entity
#NamedQueries({
#NamedQuery(
name ="PIXEL_ALL",
query = "" +
" SELECT new SourceCount(" +
" (select count(a) from PIXEL_LOG_CURR1 a " +
" where to_char(a.TIMESTAMP, 'YYYYMMDD') = :PROCDATE " +
" )," +
" (select count(b) from PIXEL_LOG_CURR2 b" +
" where to_char(b.TIMESTAMP, 'YYYYMMDD') = :PROCDATE " +
" )" +
") from Dual1" +
""
)
})
public class SourceCount {
#Id
private Long COUNT;
public SourceCount(Long COUNT1, Long COUNT2) {
this.COUNT = COUNT1+COUNT2;
}
public Long getCOUNT() {
return COUNT;
}
public void setCOUNT(Long COUNT) {
this.COUNT = COUNT;
}
}
Part of the magic here is to create a dummy table and insert one record into it. In my case, I named it dual1 because my database is Oracle, but I don't think it matters what you call the dummy table.
#Entity
#Table(name="DUAL1")
public class Dual1 {
#Id
Long ID;
}
Don't forget to insert your dummy record:
SQL> insert into dual1 values (1);
As Patrick said, appending the LISTs from each SELECT would be a good idea but remember that it acts like UNION ALL. To avoid this side effect, just control if the object is already added in final collection or not. If no, then add it.
Something else that you should care about is that if you have any JOIN in each SELECT, the result would be a list of object array(List<Object[]>) so you have to iterate over it to only keep the object that you need.
Hope it works.
Using Java JDBC, I want to collect information returned from SQL Select query.
If I fire below SQL query:
SELECT col1 AS 'Field1', col2 AS 'Field2' FROM Table;
Then, using resultSetMetaData.getColumnName(1), I get 'col1' as result, which is the expected result.
Now, the problem is, when I join 2 SQL tables (Since, MySQL does not provide Full Outer Join, hence, I fired the following query)
SELECT Table1.Col1 AS 'Field1', Table1.Col3 AS 'Field2',
Table2.Col5 AS 'Field3',Table2.Col4 AS 'Field4' FROM Table1
LEFT JOIN Table2 ON Table1.id = Table2.id
UNION
SELECT Table1.Col1 AS 'Field1', Table1.Col3 AS 'Field2',
Table2.Col5 AS 'Field3',Table2.Col4 AS 'Field4' FROM Table1
RIGHT JOIN Table2 ON Table1.id = Table2.id;
Now, using resultSetMetaData.getColumnName(1), I get 'Field1' as result, where as, I expected 'col1'.
I tried resultSetMetaData.getColumnLabel(1) also, but it still returned 'Field1'.
I want 'col1' as the result, which I could not get by any of the methods of resultSetMetaData.
Any help on this will be appreciable.
You are seeing those results because it is a UNION query. It is entirely possible that such a query could do something like
SELECT Col1 AS Field1 FROM Table1
UNION
SELECT Col2 AS Field1 FROM Table2
In that case there is no single "correct" answer if getColumnName was to try and return the name of the underlying column in the result: Should it return 'Col1' or 'Col2'?
Since any column in the result set of a UNION query can be derived from more than one underlying column, getColumnName can only return the effective name of that column, which is Field1 in the example above.
I'm joining one table to another. The join works. I want to restrict the results to records with an "Error" message that can be in either table. When I do the following, I get no results back, yet I know there should be 2.
Criteria criteria = session.createCriteria(TableName.class);
criteria.createAlias("someList", "things");
Criterion restriction1 = Restrictions.eq("status", "Error");
Criterion restriction2 = Restrictions.eq("things.anotherStatus", "Error");
criteria.add(Restrictions.or(restriction1, restriction2));
finalList = criteria.list();
I noticed that the restrictions by themselves actually work. So, if I only do the first restriction on the original table with no alias OR if I only do the second restriction on the alias table, then I get 1 result each time.
Also, a simple join SQL query like the one below works as expected:
Select count(*)
From table1 t1
Left join table2 t2 on t1.id = t2.another_id
Where t1.status = 'ERROR' or t2.anotherStatus = 'ERROR'
How can I get this right in Hibernate?
EDIT 1: I now see that Hibernate does an Inner Join when I use the #JoinColumn annotation. How can I change it to do an Outer Join instead?
EDIT 2: Even adding #Fetch(FetchMode.JOIN) still results in an inner join! What gives? The documentation clearly says it will do an outer join. The annotation now looks like this:
#OneToMany
#JoinColumn(name="ID_FK")
#Fetch(FetchMode.JOIN)
private List<Thing> things;
Answer: use criteria.createAlias("someList", "things", JoinType.LEFT_OUTER_JOIN); instead.
Explanation: When no JoinType is specified, createAlias does an inner join by default.
How to add groupBy criteria to the code below? Because if I add criteriaQuery.groupBy(from.get(minutis.Preke_.prId)); - I get exactly the same SQL statement (without groupBy):
CriteriaBuilder cb = MinutisManager.getInstance().getCriteriaBuilder();
CriteriaQuery criteriaQuery = cb.createQuery(minutis.Preke.class);
Root<minutis.Preke> from = criteriaQuery.from(minutis.Preke.class);
from.fetch(minutis.Preke_.tiekejai, JoinType.LEFT).fetch(minutis.PrekeTiekejas_.tiekejas, JoinType.LEFT);
//criteriaQuery.groupBy(from.get(minutis.Preke_.prId));
TypedQuery<minutis.Preke> typedQuery = MinutisManager.getInstance().createQuery(criteriaQuery);
typedQuery.setFirstResult(0);
typedQuery.setMaxResults(100);
typedQuery.getResultList();
EDIT 1:
criteriaQuery.distinct(true) is not an option for me. Because that command hangs the whole statement and if I use EXPLAIN:
If I use GROUP BY on the query, then EXPLAIN is:
EDIT 2:
I get this SQL statement with and without criteriaQuery.groupBy(from.get(minutis.Preke_.prId));
SELECT ... FROM preke t1 LEFT OUTER JOIN preke_tiekejas t0 ON (t0.pr_id = t1.pr_id) LEFT OUTER JOIN tiekejas t2 ON (t2.tiek_id = t0.tiek_id) LEFT OUTER JOIN gamintojas t3 ON (t3.gam_id = t1.gam_id) LEFT OUTER JOIN google_compare t4 ON (t4.pr_id = t1.pr_id) LEFT OUTER JOIN grupe t5 ON (t5.pgs_id = t1.pgs_id) LEFT OUTER JOIN preke_kaina t6 ON (t6.pr_id = t1.pr_id) ORDER BY t1.pr_id LIMIT ?, ?
The SQL for the GROUP BY query should definitely contain a GROUP BY. Ensure that you are compiling and deploying the code correctly.
It could be a bug that the group by is ignored, as normal group by queries will not select object, but aggregated values. Check that you are using the latest release, and perhaps log a bug, or try JPQL.
In general your query does not make any sense, normally on a group by query you can only select the fields that you grouped by, or aggregation functions.
Perhaps consider batch fetching instead of join fetching.
http://java-persistence-performance.blogspot.com/2010/08/batch-fetching-optimizing-object-graph.html
I will file a bug in Eclipselink, because if I change fetch line with QueryHints, everything works:
Change this (with this line I get duplicate Preke entities with populated children entities):
from.fetch(minutis.Preke_.tiekejai, JoinType.LEFT).fetch(minutis.PrekeTiekejas_.tiekejas, JoinType.LEFT);
To this (with this lines I get unique Preke entities with populated children entities):
typedQuery.setHint(QueryHints.LEFT_FETCH, "Preke.tiekejai");
typedQuery.setHint(QueryHints.LEFT_FETCH, "Preke.tiekejai.tiekejas");
I get my desired result.
EDIT 1:
The bug really exists, now max resulsts is not working. Both cases typedQuery is identical.
typedQuery.setMaxResults(100);
System.out.println(typedQuery.getResultList().size()); //prints 73
typedQuery.setMaxResults(500);
System.out.println(typedQuery.getResultList().size()); //prints 413
No problem, I found the bug report, here it is, just in case someone else needs it.Criteria api ignores group by statement
I'm trying to write a HQL/Criteria/Native SQL query that will return all Employees that are assigned to a list of Projects. They must be assigned to all Projects in order to be selected.
An acceptable way of achieving this with native SQL can be found in the answer to this question: T-SQL - How to write query to get records that match ALL records in a many to many join:
SELECT e.id
FROM employee e
INNER JOIN proj_assignment a
ON e.id = a.emp_id and a.proj_id IN ([list of project ids])
GROUP BY e.id
HAVING COUNT(*) = [size of list of project ids]
However, I want to select all fields of Employee (e.*). It's not possible to define SQL grouping by all the columns(GROUP BY e.*), DISTINCT should be used instead. Is there a way to use DISTINCT altogether with COUNT(*) to achieve what I want?
I've also tried using HQL to perform this query. The Employee and ProjectAssignment classes don't have an association, so it's not possible to use Criteria to join them. I use a cross join because it's the way to perform a Join without association in HQL. So, my HQL looks like
select emp from Employee emp, ProjectAssignment pa
where emp.id = pa.empId and pa.paId IN :list
group by emp having count(*) = :listSize
However, due to a bug in Hibernate, GROUP BY entity does not work. The SQL it outputs is something like group by (emptable.id).
Subquerying the assignment table for each project (dynamically adding and exists (select 1 from proj_assignment pa where pa.emp_id=e.id and pa.proj_id = [anId]) for each project in the list) is not an acceptable option.
Is there a way to write this query properly, preferrably in HQL (in the end I want a List<Employee>), without modifying mappings and without explicitly selecting all columns in the native SQL ?
EDIT: I'm using Oracle 10g and hibernate-annotations-3.3.1.GA
How about:
select * from employee x where x.id in(
SELECT e.id
FROM employee e
INNER JOIN proj_assignment a
ON e.id = a.emp_id and a.proj_id IN ([list of project ids])
GROUP BY e.id
HAVING COUNT(*) = [size of list of project ids]
)
I've found an alternative way to achieve this in HQL, it's far more inefficient than what I'd like, (and than what is really possible without that nasty bug) but at least it works. It's better than repeating subselects for each project like
and exists (select 1 from project_assignment pa where pa.id = someId and pa.emp_id = e.id)
It consists of performing a self-join subquery in order to find out, for each of the Employees, how many of the projects in the list they are assigned to, and restrict results to only those that are in all of them.
select e
from Employee
where :listSize =
(select distinct count(*)
from Employee e2, ProjectAssignment pa
where
e2.id = pa.id_emp and
e.id = e2.id
and pa.proj_id IN :projectIdList
)