Does anyone know if there's an easy way to negate a parse query? Something like this:
Parse.Query.not(query)
More specifically I want to do a relational query that gets everything except for the objects within the query. For example:
const relation = myParseObject.relation("myRelation");
const query = relation.query();
const negatedQuery = Parse.Query.not(query);
return await negatedQuery.find();
I know one solution would be to fetch the objects in the relation and then create a new query by looping through the objectIds using query.notEqualTo("objectId", fetchedObjectIds[i]), but this seems really circuitous...
Any help would be much appreciated!
doesNotMatchKeyInQuery is the solution as Davi Macedo pointed out in the comments.
For example, if I wanted to get all of the Comments that are not in an Article's relation, I would do the following:
const relationQuery = article.relation("comments").query();
const notInRelationQuery = new Parse.Query("Comment");
notInRelationQuery.doesNotMatchKeyInQuery("objectId", "objectId", relationQuery);
const notRelatedComments = await notInRelationQuery.find();
How I understand it is that the first argument is specifying the key in the objects that we are fetching. The second argument is specifying the key in the objects that are in the query that we're about to argue. And lastly we argue a query for the objects we don't want. So, it essentially finds the objects you don't want and then compares the values of the objects you do want to the values of the objects you don't want for the argued keys. It then returns all the objects you do want. I could probably write that more succinctly, but w/e.
Related
i'm using Apollo Client do request a very structured dataset from my server. Something like
-Show
id
title
...
-Seasons
number
-Episodes
id
number
airdate
Thanks to normalization my episodes are stored individually but i cannot query them. For exemple i would like to query all the episodes to then sort them by date to display coming next.
the only way i see is to either 'reduce' my show list to an array of episode and then do the filtering. Or to do a new query to the server.
But it will be so much faster if I could get a list of all Episodes in cache.
Unfortunately with readFragment you can only query One object by its id.
Question:
Is there a way to query the cache for all object of a defined type?
The answer is late, but could have helped someone else, currently apollo does not support it. This is the issue here from github, and also a work around.
https://github.com/apollographql/apollo-client/issues/4724#issuecomment-487373566
Here is the copied workaround by #superandrew213
const serializedState = client.cache.extract()
const typeNameItems = Object.values(serializedState)
.filter(item => item.__typename === 'TypeName')
.map(item => client.readFragment({
fragmentName: 'FragmentName',
fragment: Fragment,
id: item.id,
}))
Please take note that this method is slow, especially if you have a large normalized data.
How do we find if any element of an array is part of another array in a query?
var followers = []; // Array of Parse User pointers
query.howTo("attending", followers); // attending is an array of User Pointers.
That is, the query should match if any one or more of the elements in followers exists in attending.
query.containsAll matches for all the elements. Is there something like query.containsSome ?
I was pretty sure you can query two arrays. Take a look into the docs to check better.
In case it doesn't, you can use compound queries.
For example, generate an array of queries, based on the array of followers. The [forEach] is a better idea in this case, but I'm supposing here a for loop.
var followers = []; //array of users
var mainQuery = new Parse.Query(YourOtherObject);
//for each one of followers
var orQuery = new Parse.Query(YourOtherObject);
orQuery.equalTo("attending", follower);
mainQuery = Parse.Query.or(mainQuery, orQuery);
This solution might not be performant if your followers areay is too big. But in any case, I still recommend using relations in this case, as you benefit from the inverse, and can get from the users query, where he is present as attending in the other Object.
There is a table, it is a poco entity generated by entity framework.
class Log
{
int DoneByEmpId;
string DoneByEmpName
}
I am retrieving a list from the data base. I want distinct values based on donebyempid and order by those values empname.
I have tried lot of ways to do it but it is not working
var lstLogUsers = (context.Logs.GroupBy(logList => logList.DoneByEmpId).Select(item => item.First())).ToList(); // it gives error
this one get all the user.
var lstLogUsers = context.Logs.ToList().OrderBy(logList => logList.DoneByEmpName).Distinct();
Can any one suggest how to achieve this.
Can I just point out that you probably have a problem with your data model here? I would imagine you should just have DoneByEmpId here, and a separate table Employee which has EmpId and Name.
I think this is why you are needing to use Distinct/GroupBy (which doesn't really work for this scenario, as you are finding).
I'm not near a compiler, so i can't test it, but...
Use the other version of Distinct(), the one that takes an IEqualityComparer<TSource> argument, and then use OrderBy().
See here for example.
Im using entity framework 4 and linq/lamda expressions. Im sure its an easy one but im trying to query a collection with an array but get records which contain all the arrays values.
basically what im doing is this
var records = collection.where(x.classifications.Any(y=> Array.Contains(y.ClassificationID))).ToList()
This works in a sense that it returns records that contain any of the arrays values but how do i get only records that contain all of the values in the array.
Hope that makes sense
EDIT:
Im marking the comment below as the answer as I did have to use ALL in my query to get it to work, however I also had to re - write my query slightly. This is what i eventually had...
var records = collection.Where(x=> Array.All(c=> x.Classifications.Select(l=>l.ClassificationID).Contains(c)))
What about using All instead of Any?
var records = collection.Where(x => x.classifications.All(y => Array.Contains(y.ClassificationID)))
.ToList()
I am new to LINQ queries and to EF too, I usually work with MySQL and I can't guess how to write really simples queries.
I'd like to select all results from a table. So, I used like this:
ZXContainer db = new ZXContainer();
ViewBag.ZXproperties = db.ZXproperties.All();
But I see that I have to write something inside All(---).
Could someone guide me in how could I do that? And if someone has any good link for references too, I thank so much.
All() is an boolean evaluation performed on all of the elements in a collection (though immediately returns false when it reaches an element where the evaluation is false), for example, you want to make sure that all of said ZXproperties have a certain field set as true:
bool isTrue = db.ZXproperties.All(z => z.SomeFieldName == true);
Which will either make isTrue true or false. LINQ is typically lazy-loading, so if you're calling db.ZXproperties directly, you have access to all of the objects as is, but it isn't quite what you're looking for. You can either load all of the objects at the variable assignment with an .ToList():
ViewBag.ZXproperties = db.ZXproperties.ToList();
or you can use the below expression:
ViewBag.ZXproperties = from s in db.ZXproperties
select s;
Which is really no different than saying:
ViewBag.ZXproperties = db.ZXproperties;
The advantage of .ToList() is that if you are wanting to do multiple calls on this ViewBag.ZXproperties, it will only require the initial database call when it is assigning the variable. Alternatively, if you do any form of queryable action on the data, such as .Where(), you'll have another query performed, which is less than ideal if you already have the data to work with.
To select everything, just skip the .All(...), as ZXproperties allready is a collection.
ZXContainer db = new ZXContainer();
ViewBag.ZXproperties = db.ZXproperties;
You might want (or sometimes even need) to call .ToList() on this collection before use...
You don't use All. Just type
ViewBag.ZXproperties = db.ZXproperties;
or
ViewBag.ZXproperties = db.ZXproperties.ToList();
The All method is used to determine if all items of collection match some condition.
If you just want all of the items, you can just use it directly:
ViewBag.ZXproperties = db.ZXproperties;
If you want this evaluated immediately, you can convert it to a list:
ViewBag.ZXproperties = db.ZXproperties.ToList();
This will force it to be pulled across the wire immediately.
You can use this:
var result = db.ZXproperties.ToList();
For more information on linq see 101 linq sample.
All is some checking on all items and argument in it, called lambda expression.