I'm trying to sort a table of data. I have the following domain (paraphrased and example-ified):
class Car {
Engine engine
static constraints = {
engine nullable: true // poor example, I know
}
}
class Engine {
String name
}
Here's the controller action that's handling the sort:
def myAction = {
def list = Car.findAll(params)
render(view: 'list', model: [list: list])
}
I provision some data such that there are several Cars, some with null engines and others with engines that are not null.
I attempt the following query:
http://www.example.com/myController/myAction?sort=engine.name&order=asc
The results from the query only return Car entries whose engine is not null. This is different from the results that would be returned if I only queried the association (without its property):
http://www.example.com/myController/myAction?sort=engine&order=asc
which would return all of the Car results, grouping the ones with null engines together.
Is there any way that:
I can get the query that sorts by the association property to return the same results as the one that sorts by only the association (with the null associations grouped together)?
I can achieve those results using the built-in sorting passed to list() (i.e. without using a Criteria or HQL query)
You need to specify LEFT_JOIN in the query, try this:
import org.hibernate.criterion.CriteriaSpecification
...
def list = Car.createCriteria().list ([max:params.max?:10, offset: params.offset?:0 ]){
if (params.sort == 'engine.name') {
createAlias("engine","e", CriteriaSpecification.LEFT_JOIN)
order( "e.name",params.order)
} else {
order(params.sort, params.order)
}
}
Remember to put engine.name as the property to order by in your list.gsp
<g:sortableColumn property="engine.name" title="Engine Name" />
Related
How do I sort on a nested field (or a virtual attribute) in graphql-ruby?
ExampleType = GraphQL::ObjectType.define do
name 'Example'
description '...'
field :nested_field, NestedType, 'some nested field' do
// some result that is virtually calculated and returns
OpenStruct.new(a: 123//some random number, b: 'some string')
end
end
QueryType = GraphQL::ObjectType.define do
name 'query'
field: example, ExampleType do
resolve -> (_obj, args,_ctx) {
Example.find(args['id']) //Example is an active record
}
end
field: examples, types[ExampleType] do
resolve -> (_obj, args,_ctx) {
// NOTE: How to order by nested field here?
Example.where(args['id'])
}
end
end
And if I am trying to get a list of examples ordered by nested_field.a:
query getExamples {
examples(ids: ["1","2"], order: 'nested_field.a desc') {
nested_field {
a
}
}
}
You can not order Active record by virtual attribute, because Active record can not match this virtual attribute to SQL/NoSQL query. You can avoid limitation, by creating view at DB layer. In GraphQL, sorting/pagination should be implemented at DB layer. Without that sorting/pagination implementation queries all data from DB to application memory.
Also, I want to recommend you switching from order argument with string type to sort argument with [SearchSort!] type based on enums. GraphQL schema will looks like that:
input SearchSort {
sorting: Sorting!
order: Order = DESC
}
enum Sorting {
FieldName1
FieldName2
}
enum Order {
DESC
ASC
}
It helps you implement mapping from GraphQL subquery to DataBase query.
This works fine
query QryTopics {
topics {
nodes {
name
topicId
count
}
}
}
But I want a filtered result. I'm new to graphql but I see a param on this collection called 'where', after 'first', 'last', 'after' etc... How can I use that? Its type is 'RootTopicsTermArgs' which is likely something autogenerated from my schema. It has fields, one of which is 'childless' of Boolean. What I'm trying to do, is return only topics (a custom taxonomy in Wordpress) which have posts tagged with them. Basically it prevents me from doing this on the client.
data.data.topics.nodes.filter(n => n.count !== null)
Can anyone direct me to a good example of using where args with a collection? I have tried every permutation of syntax I could think of. Inlcuding
topics(where:childless:true)
topics(where: childless: 'true')
topics(where: new RootTopicsTermArgs())
etc...
Obviously those are all wrong.
If a custom taxonomy, such as Topics, is registered to "show_in_graphql" and is part of your Schema you can query using arguments like so:
query Topics {
topics(where: {childless: true}) {
edges {
node {
id
name
}
}
}
}
Additionally, you could use a static query combined with variables, like so:
query Topics($where:RootTopicsTermArgs!) {
topics(where:$where) {
edges {
node {
id
name
}
}
}
}
$variables = {
"where": {
"childless": true
}
};
One thing I would recommend is using a GraphiQL IDE, such as https://github.com/skevy/graphiql-app, which will help with validating your queries by providing hints as you type, and visual indicators of invalid queries.
You can see an example of using arguments to query terms here: https://playground.wpgraphql.com/#/connections-and-arguments
Using Orchard CMS, I am dealing with a record and a part proxy, but cannot figure out how to save it into the DB. In fact, I confess I don't even know how to get the items I'm trying to save into this paradigm. I was originally using enum's for choices:
MyEmum.cs:
public enum Choices { Choice1, Choice2, Choice3, Choice4 }
MyRecord.cs:
public virtual string MyProperty { get; set; }
MyPart.cs:
public IEnumerable<string> MyProperty
{
get
{
if (String.IsNullOrWhiteSpace(Record.MyProperty)) return new string[] { };
return Record
.MyProperty
.Split(new[] { '.' }, StringSplitOptions.RemoveEmptyEntries)
.Select(r => r.Trim())
.Where(r => !String.IsNullOrEmpty(r));
}
set { Record.MyProperty = value == null ? null : String.Join(",", value); }
}
Now, in my service class, I tried something like:
public MyPart Create(MyPartRecord record)
{
MyPart part = Services.ContentManager.Create<MyPart>("My");
...
part.MyProperty = record.MyProperty; //getting error here
...
return part;
}
However, I am getting the following error: Cannot implicitly convert 'string' to System.Collections.Generic.IEnumerable<string>'
Essentially, I am trying to save choices from a checkboxlist (one or more selections) as a comma-separated list in the DB.
And this doesn't even get me over the problem of how do I use the enum. Any thoughts?
For some background:
I understand that the appropriate way to handle this relationship would be to create a separate table and use IList<MyEnum>. However, this is a simple list that I do not intend to manipulate with edits (in fact, no driver is used in this scenario as I handle this on the front-end with a controller and routes). I am just capturing data and redisplaying it in the Admin view for statistical/historical purposes. I may even consider getting rid of the Part (considering the following post: Bertrand's Blog Post.
It should be:
part.MyProperty = new[] {"foo", "bar"};
for example. The part's setter will store the value on the record's property as a comma-separated string, which will get persisted into the DB.
If you want to use enum values, you should use the Parse and ToString APIs that .NET provide on Enum.
I have two classes - MyBaseClass and BaseClassContainer - that are declared like such:
public class MyBaseClass
{
private Guid id;
public Guid ID
{
if (id == Guid.Empty)
{
id = Guid.NewGuid();
}
return id;
}
//...Other Properties omitted for brevity
}
and
public class BaseClassContainer : INotifyPropertyChanged
{
private ObservableCollection<MyBaseClass> baseClasses;
public ObservableCollection<MyBaseClass> BaseClasses
{
//...Omitted for brevity...
}
}
Then in my code I have an ObservableCollection of type BaseClassContainer (BaseClassContainerCollection). What I'm trying to figure out is how can I use LINQ to select a single BaseClassContainer from the ObservableCollection where one of its MyBaseClass.ID matches a specific Guid. The reason I'm using the Single() method is because I know they're all going to be unique.
I've tried the following but it doesn't work:
var result = BaseClassContainerCollection.Single(container => container.BaseClasses.Single(baseClass => baseClass.ID == specificGuid));
I get an error saying: Cannot implicitly convert type 'MyBaseClass' to 'bool'. What am I missing?
Lets break apart your query:
BaseClassContainerCollection.Single(yourPredicate);
Single, as it is used here, basically says "filter BaseClassContainerCollection on this predicate" (a "filter" function that evaluates to true or false for whether or not to include it in the results). Instead of a function that returns true/false, you're saying you want it to evaluate to a MyBaseClass, which doesn't make sense. Your inner call to Single makes sense, because x => x.Id == guid is a function that returns true/false and filters to only those elements that meet the criteria (then states that you know there will only be one of them in the results or else throw an exception).
What you want to do is Select the single MyBaseClass result from the inner query, then call Single on the result (without a predicate) since you know the result should only have one item returned. I believe you're looking for:
BaseClassContainerCollection.Select(container => container.BaseClasses.Single(baseClass => baseClass.ID == specificGuid)).Single();
I have a couple of DBML generated classes which are linked together by an id, e.g.
ClassA {
AID,
XID,
Name
}
ClassB {
AID,
ExtraInfo,
ExtraInfo2
}
In using something like db.ClassAs.Where(XID == x) and iterating through that result,
it ends up executing a query for each of the ClassAs and each of ClassBs, which is slow.
Alternatively, I've tried to use ExecuteQuery to fetch all the info I care about and have that return a ClassA. In iterating over that I end up with it doing the same, i.e. doing alot of individual fetches vs. just 1. If I store it in a ClassC (that is not associated with a DB entity) which has the fields of interest of both ClassA and ClassB, this query is much faster, but it's annoying b/c I just created IMO an unnecessary ClassC.
How can I still use ClassA, which associates to ClassB, and still use ExecuteQuery to run 1 query vs. A*B number of queries?
If you have associations you shouldn't need to use ExecuteQuery().
Here's an example using some imaginary Book Library context and anonymous types for the result:
var results =
Books
.Where(book => book.BookId == 1)
.Select(book =>
new
{
book.Name,
AuthorName = book.Author.Name, //Is a field in an associated table.
book.Publisher, //Is an associtated table.
});
EDIT: without anon types
var results =
Books
.Where(book => book.BookId == 1)
.Select(book =>
new BookResult()
{
BookName = book.Name,
AuthorName = book.Author.Name, //Is a field in an associated table.
Publisher = book.Publisher, //Is an associtated table.
});