Develop Reference

Firebase Firestore OR query (Android Studio)

I've been trying to find a query for almost 2 days now
I want to search id (current user id) from the document 4 fields (customer1,customer2,customer3,customer4)
Here is the firestore document picture
tried this query
final Query userQuery = collectionReference
.whereEqualTo("customer1",firebaseAuth.getInstance().getCurrentUser().getUid())
.whereEqualTo("customer2",firebaseAuth.getInstance().getCurrentUser().getUid())
.whereEqualTo("customer3",firebaseAuth.getInstance().getCurrentUser().getUid())
.whereEqualTo("customer4",firebaseAuth.getInstance().getCurrentUser().getUid());
but this only shows up if the current ID is present in all 4. Is there any easier way to do this.

You can do that by using a field that is an array containing the uids you want to test, and then applying array-contains on it. In your case:
In your case:
customer: [customer1, customer2, customer3, customer4]
collectionReference
.where("customer ", "array-contains", firebaseAuth.getInstance().getCurrentUser().getUid())

Firestore does not support logical OR queries among mulitple fields. So, what you're trying to do is not possible with a single query using the database structure you have now. You would have to perform multiple queries and merge the results in the client.
If you want to be able to use a single query, you will have to change your database. One option is to put all the customers into a single array field and use an array-contains query to find a customer in that field.

Is it possible to use Where In with a Collection Group query in Firestore?

In my database:
-Users(Top level collection):
---user1(doc):
----------pets(sub collection):
--------------pet1(doc)
--------------pet2(doc)
---user2(doc):
----------pets(sub collection):
--------------pet3(doc)
--------------pet4(doc)
If i have a List of ids: list("pet2", "pet3", "pet4)
Is there a way to do something like this and get a back a List of DocumentsSnapshots?
firestore.collectionGruop("pets")whereIn(FieldPath.documentId(), list)
It works with a root collection but i dont know if this is possible with a collection group

A collection group query is the only place where a filter on FieldPath.documentId() does not work the way you expect. That's because of some details about the way that this token actually works. If you try to this anyway, you will get an error like this:
Invalid query. When querying a collection group by FieldPath.documentId(), the value provided must result in a valid document path, but 'x' is not because it has an odd number of segments.
If you want to do a filter on document IDs in a collection group query, you will need to store the ID of the document as the value of a field in each document. If you use the field called "id", then you can filter on that field like this:
firestore
.collectionGruop("pets")
.whereIn('id', list)
This will give you a different error saying that you need to create an index, and give you a link to do so. After you create that index (it might take some time), you should be good to go.
See also: How to perform collection group query using document ID in Cloud Firestore

Doing queries on firebase

I use firebase in my android app, but i'm facing problems. For example. I have this entrie
persons
-kskhdhksdhh
name:"Vladimir"
age:"25"
sexe:"M"
country:"Russia"
-jhgsdhghsgs
name:"Victoria"
age:"20"
sexe:"F"
country:"England"
-zejhbshevzh
name:"John"
age:"44"
sexe:"M"
country:"England"
I want to select males living in England. How do I rearrange my data to get there knowing we can not do two orderby

First - take a look at this answer , for similar question:
Query based on multiple where clauses in firebase
Anyway, you can add country level to your data structure, so your data can look something like:
persons
-Russia
-kskhdhksdhh
name:"Vladimir"
age:"25"
sexe:"M"
-England
-jhgsdhghsgs
name:"Victoria"
age:"20"
sexe:"F"
-zejhbshevzh
name:"John"
age:"44"
sexe:"M"
Then you can easily query for males living in England.
Another option that described in the link on the top , is to add a key that combine both country & gender, and then query this property.

Android Parse query for data from more than two tables

I am using Parse for one of my android application and struggling for a query to get output.
Application Parse DB has three table which is as described below-
User: user related information with unique object Id
Post: Contains Post related information with unique object Id and UserId(Pointer to user table) who create the post
Like: UserId(Pointer to user table) represent who is Liking the post, PostId(Pointer to post table) which post is liking and unique
object Id
Now I want to make a single compound query for All post for a specific user along-with total number of likes to corresponding post. Please suggest a solution/query for that

When a user creates a post, assign the user objectID to some post identifier property in the post table.
To retrieve all posts from a user, a query like this may help:
query.whereEqualTo("objectID", currentUser.objectID)
If you're just concerned about the like count, rather than each user who has liked the post, you may want to have an Integer value in the post table that is incremented after a user presses the like button on that post.

You should create your own webHook.
Following this exemples here you can easily learn and develop your own stuff, you can even add some triggers to your application!
https://parse.com/docs/cloudcode/guide#cloud-code-cloud-functions
https://parse.com/docs/cloudcode/guide#cloud-code-beforesave-triggers

If User table doesn't have Post<.Relation> column
I suggest you to read about how to join queries.
f.g. make a query1 to get the user, then another query2 to get all posts with whereMatchesQuery('UserColumnInPostTable', query1) function.
Now, you are going to get all posts of a specific user efficiently.
.
If User table have Post<.Relation> column
this is the easiest way
Just get the user object and get the relation object, then get the query, and find in background

Content Provider filtering query, filtering Cursor

I got following problem, I need to use a Content Provider to read a
Database of an other App.
first I want all rows, and after analyzing the data only e.g. the rows
from _id = 1, 3 and 5.
how can I call a Content provider and select only these rows?
or is it possible to create a subset Cursor form an given Cursor?
Thanks in advance.

If you're talking to another app, I assume you're querying the other app's ContentProvider to get the data from them in the first place.
In this situation, the cleanest answer seems not to build your own ContentProvider that filters/wraps theirs. Instead query their ContentProvider from your application directly, and use the select clause in your query() to specify the conditions that define the subset of data you want to be given.