I am trying to find the proper syntax for a query that I know has got to be very common but couldn't find a code example for.
class ObjA {
...
static hasMany = [b:ObjB]
}
if a is an instance of ObjA, I want to perform a query like:
a.b.findAllBsSuchThat(b.someproperty = somevalue)
In order to avoid (N+1) queries for lazy associations per a, you can use a criteria as:
ObjA.withCriteria {
b {
eq 'someProperty', someValue
}
}
or where queries:
ObjA.where { b.someProperty == somevalue }.list()
If you use something like a.b.findAllBsSuchThat(b.someproperty = somevalue) then you would be getting all b's for a and then filtering on the result. This will affect the performance and will unnecessary.
Related
I have a domain class
class Url {
UUID id
String url
static hasMany = [
indications:UrlIndication
]
...
}
And
class UrlIndication {
UUID id
String name
static belongsTo = Url
...
}
I want to choose urls so that it has all the necessary UrlIndication elements in a given list indicationsId.
For that I use an association and criteria like this one:
indications {
and {
indicationsId.each{
indication->
eq ('id',UUID.fromString(indication as String))
}
}
}
However, all I got is an empty result. Can you suggest any modifications/ other methods so that I can do this? Thanks in advance
Your query returned an empty list because it's the equivalent of the expression (pseudo-code): if 1 = 1 and 1 = 2 and 1 = 3
Such an expression would always be false. in or inList would not work for the reason #innovatism described.
In theory, Criteria's eqAll() or HQL's = ALL would work. But, I don't know for sure because I could not get either one to work.
What will work is to use inList to return a subset of Urls: those which contain at least one of the UrlIndication IDs. Then use Groovy's containsAll() to finish the job.
def ids = indicationsId.collect { UUID.fromString(it as String) }
Url.createCriteria()
.buildCriteria {
indications {
inList 'id', ids
}
}
.setResultTransformer(org.hibernate.Criteria.DISTINCT_ROOT_ENTITY)
.list()
.findAll {
it.indications.id.containsAll(ids)
}
Since the query has the potential to return duplicate Url instances, the ResultTransformer is set to return a unique list.
Finally, findAll() is used along with containsAll() to filter the list further.
Using eqAll (maybe)
Something like the following might work. Something funky is going on with Grails' HibernateCriteriaBuilder that causes the eqAll method to look up properties in the root entity; completely ignoring the sub criteria. So the following uses Hibernate directly. It didn't work for me, but it's as close as I could get. And it gave me a head-ache!
Url.createCriteria().buildCriteria {}
.createCriteria('indications', 'i')
.add(org.hibernate.criterion.Property.forName('i.id').eqAll(org.hibernate.criterion.DetachedCriteria.forClass(UrlIndication)
.add(org.hibernate.criterion.Restrictions.in('id', ids))
.setProjection(org.hibernate.criterion.Property.forName('id'))
))
.setResultTransformer(org.hibernate.Criteria.DISTINCT_ROOT_ENTITY)
.list()
The problem I had is I could not get Restrictions.in to work. Restrictions.eq works fine.
the in clause should do:
indications {
'in' 'id', indicationsId.collect{ UUID.fromString indication.toString() }
}
I have, for example, the following domain objects:
class A {
B b
static constraints = {
b nullable: true
}
}
class B {
}
Given instance of A, I would like to fetch only the id of B.
I tried the following, but received null every time:
def id = a.bId
Is it possible to fetch the id of b without doing a.b.id ?
You will need to enhance your domain to use GORM based mapping hints (given to Hibernate) to accomplish this.
Your domain could look something like this:
class A {
static hasOne = [b: B]
}
class B {
// stuff
}
Using the hasOne will allow Hibernate to manage the association and thus allows you to use the a.bId notation.
Hope this helps.
I have a domain object (Cat) like this:
class Cat {
String name
static hasMany = [
nicknames: String
]
}
(A cat has a name, and also has many nicknames (which are Strings))
And I am trying to query all the cats with certain nicknames.
I've tried this:
PagedResultList getCatsByNickname(String nickname, Map params) {
PagedResultList results = Cat.createCriteria().list(params) {
'ilike'('nicknames','%'+nickname+'%')
}
return results
}
But it never returns any results. (If I change the query to just use the simple name attribute, it works finding all cats with that name, but I want to query against the nicknames.)
I also tried this:
PagedResultList getCatsByNickname(String nickname, Map params) {
PagedResultList results = Cat.createCriteria().list(params) {
'nicknames' {
'ilike'('nicknames','%'+nickname+'%')
}
}
return results
}
But I get the error: org.hibernate.MappingException: collection was not an association: example.Cat.nicknames
So the question is, how do I query against a hasMany of type String?
After a lot of trying and researching, I found this will work with Grails 2.4.0, I don't know about older versions.
Cat.withCriteria {
createAlias('nicknames', 'n')
ilike 'n.elements', '%kitty%'
}
The trick is to use 'n.elements'
You can use HQL for querying in such a scenario. For example,
Cat.findAll("from Cat c where :nicknames in elements(c.nicknames)", [nicknames:'kitty'])
You can also use HQL (tested with Grails 2.5.0):
Cat.findAll("from Cat c inner join c.nicknames as n where upper(n) like '%'||?||'%'", [nickname.toUpperCase()])
I have two very similar methods in Grails, something like "calculate statistics by os" and "calculate statistics by browser" - effectively both prepare some things, then run a similar query on the DB, then do things with the results. The only part where the methods differ is the query they run in the middle of my method -
def summary = c.list {
eq('browser', Browser.get(1)) // OR eq('os', OS.get(1))
between('date', dates.start, dates.end)
}
It occurred to me that the ideal way to refactor it would be to pass in the first line of the closure as a method parameter. Like
doStats (Closure query) {
...
def summary = c.list {
query
between('date', dates.start, dates.end)
}
}
I tried this but "query" gets ignored. I tried query() instead but then the query clause is executed where defined, so this doesn't work either. I suppose I could just pass the whole closure as a parameter but that seems wrong - the query might also get more complicated in future.
Anyone have any better ideas?
I found leftShift operator useful for composing closure from two separate ones. What you can do is:
Closure a = { /*...*/ }
Closure b = { /*...*/ }
Closure c = a << b
Take a look at this example:
def criteria = {
projection Projections.distinct(Projections.property('id'))
and {
eq 'owner.id', userDetails.id
if (filter.groupId) {
eq 'group.id', filter.groupId
}
}
}
List<Long> ids = Contact.createCriteria().list(criteria << {
maxResults filter.max
firstResult filter.offset
})
Integer totalCount = Contact.createCriteria().count(criteria)
What you can see here is that I'm creating a criteria for listing ant counting GORM objects. Criterias for both cases are almost the same, but for listing purposes I also need to include limit and offset from command object.
You're using the criteria DSL which might be different than plain groovy closures.
To do what you're asking, you can use the method described here -
http://mrhaki.blogspot.com/2010/06/grails-goodness-refactoring-criteria.html
and put your query in to private method.
The more elegant solution for this is to use named queries in grails -
http://grails.org/doc/latest/ref/Domain%20Classes/namedQueries.html
Look at the
recentPublicationsWithBookInTitle {
// calls to other named queries…
recentPublications()
publicationsWithBookInTitle()
}
example -
Not sure about with the Grails Criteria builder, but with other builders, you can do something like:
doStats (Closure query) {
def summary = c.list {
query( it )
between('date', dates.start, dates.end)
}
}
And call this via:
def f = { criteria ->
criteria.eq( 'browser', Browser.get( 1 ) )
}
doStats( f )
If not, you're probably best looking at named queries like tomas says
I am using Nimble and Shiro for my security frameworks and I've just come accross a GORM bug. Indeed :
User.createCriteria().list {
maxResults 10
}
returns 10 users whereas User.list(max: 10) returns 9 users !
After further investigations, I found out that createCriteria returns twice the same user (admin) because admin has 2 roles!!! (I am not joking).
It appears that any user with more than 1 role will be returned twice in the createCriteria call and User.list will return max-1 instances (i.e 9 users instead of 10 users)
What workaround can I use in order to have 10 unique users returned ?
This is a very annoying because I have no way to use pagination correctly.
My domain classes are:
class UserBase {
String username
static belongsTo = [Role, Group]
static hasMany = [roles: Role, groups: Group]
static fetchMode = [roles: 'eager', groups: 'eager']
static mapping = {
roles cache: true,
cascade: 'none',
cache usage: 'read-write', include: 'all'
}
}
class User extends UserBase {
static mapping = {cache: 'read-write'}
}
class Role {
static hasMany = [users: UserBase, groups: Group]
static belongsTo = [Group]
static mapping = { cache usage: 'read-write', include: 'all'
users cache: true
groups cache: true
}
}
Less concise and clear, but using an HQL query seems a way to solve this problem. As described in the Grails documentation (executeQuery section) the paginate parameters can be added as extra parameters to executeQuery.
User.executeQuery("select distinct user from User user", [max: 2, offset: 2])
this way you can still use criteria and pass in list/pagination paramaters
User.createCriteria().listDistinct {
maxResults(params.max as int)
firstResult(params.offset as int)
order(params.order, "asc")
}
EDIT: Found a way to get both! Totally going to use it now
http://www.intelligrape.com/blog/tag/pagedresultlist/
If you call createCriteria().list() like this
def result=SampleDomain.createCriteria().list(max:params.max, offset:params.offset){
// multiple/complex restrictions
maxResults(params.max)
firstResult(params.offset)
} // Return type is PagedResultList
println result
println result.totalCount
You will have all the information you need in a nice PagedResultList format!
/EDIT
Unfortunately I do not know how to get a combination of full results AND max/offset pagination subset in the same call. (Anyone who can enlighten on that?)
I can, however, speak to one way I've used with success to get pagination working in general in grails.
def numResults = YourDomain.withCriteria() {
like(searchField, searchValue)
order(sort, order)
projections {
rowCount()
}
}
def resultList = YourDomain.withCriteria() {
like(searchField, searchValue)
order(sort, order)
maxResults max as int
firstResult offset as int
}
That's an example of something I'm using to get pagination up and running. As KoK said above, I'm still at a loss for a single atomic statement that gives both results. I realize that my answer is more or less the same as KoK now, sorry, but I think it's worth pointing out that rowCount() in projections is slightly more clear to read, and I don't have comment privileges yet :/
Lastly: This is the holy grail (no pun intended) of grails hibernate criteria usage references; bookmark it ;)
http://www.grails.org/doc/1.3.x/ref/Domain%20Classes/createCriteria.html
Both solutions offered here by Ruben and Aaron still don't "fully" work for pagination
because the returned object (from executeQuery() and listDistinct) is an ArrayList
(with up to max objects in it), and not PagedResultList with the totalCount property
populated as I would expect for "fully" support pagination.
Let's say the example is a little more complicated in that :
a. assume Role has an additional rolename attribute AND
b. we only want to return distinct User objects with Role.rolename containing a string "a"
(keeping in mind that a User might have multiple Roles with rolename containing a string "a")
To get this done with 2 queries I would have to do something like this :
// First get the *unique* ids of Users (as list returns duplicates by
// default) matching the Role.rolename containing a string "a" criteria
def idList = User.createCriteria().list {
roles {
ilike( "rolename", "%a%" )
}
projections {
distinct ( "id" )
}
}
if( idList ){
// Then get the PagedResultList for all of those unique ids
PagedResultList resultList =
User.createCriteria().list( offset:"5", max:"5" ){
or {
idList.each {
idEq( it )
}
}
order ("username", "asc")
}
}
This seems grossly inefficient.
Question : is there a way to accomplish both of the above with one GORM/HQL statement ?
You can use
User.createCriteria().listDistinct {
maxResults 10
}
Thanks for sharing your issue and Kok for answering it. I didn't have a chance to rewrite it to HQL. Here is my solution (workaround): http://ondrej-kvasnovsky.blogspot.com/2012/01/grails-listdistinct-and-pagination.html
Please tell me if that is useful (at least for someone).