filtering.md

Filtering, Ordering & Paginating queries

Filtering queries

Document queries can be filtered using where query of firebase. We have support for every where query of firebase as graphql where arguments.

For example, if you want to query all users with age>30 you have to use _gt key suffix in where filter. Example dart code would be:

Map users = await Firegraph.resolve(FirebaseFirestore.instance, r'''
query{
    users(where:{
        age_gt: 30
    }){
        id
        name
        age
    }
}
''');

so for any key, its suffix determines the operator. all the supported filters with suffixes are listed below.

Where filter	Suffix	Accepted values
.where(key, isEqualTo: value)	key_eq: value	any
.where(key, isNotEqualTo: value)	key_neq: value	any
.where(key, isGreaterThan: value)	key_gt: value	any
.where(key, isGreaterThanOrEqualTo: value)	key_gte: value	any
.where(key, isLessThan: value)	key_lt: value	any
.where(key, isLessThanOrEqualTo: value)	key_lte: value	any
.where(key, isNull: value)	key_null: value	boolean
.where(key, arrayContains: value)	key_contains: value	any
.where(key, arrayContainsAny: value)	key_containsAny: value	List
.where(key, whereIn: value)	key_in: value	List
.where(key, whereNotIn: value)	key_notIn: value	List

These filters can be applied to any collection or subcollection query, whether nested any deep! and in any amount.

You can construct a crazy query like this, and its still legit!

Map users = await Firegraph.resolve(FirebaseFirestore.instance, r'''
query{
    posts(where:{
        likes_gt: 100,
        views_lt: 5000,
        category_in: ["photography", "music"]
    }){
        id
        body
        date
        comments(where:{
            date_gt: "2021-07-27T00:00:00.999Z",
            likes_gt: 10
        }){
            id
            message
        }
    }
    users(where:{
        age_lt:35,
        favourite_color_null:false,
        hobbies_containsAny:["singing","photography"],

    }){
        id
        name
        age
        hobbies
        favourite_color
    }
}
''');

NOTE: For some queries you must have indexes already created in your firebase project

To create or view indexes in your firebase project, follow this link

Ordering queries

Document queries can be ordered using orderBy query of firebase. You can supply an orderBy argument of object type, defining the fields you want to sort by and the order of those fields as ascending or descending.

For example, if you want to query the users in ascending order of their age, your query would look like:

Map users = await Firegraph.resolve(FirebaseFirestore.instance, r'''
query{
    users(orderBy:{
        age: "asc"
    }){
        id
        name
        age
    }
}
''');

Now, if you want to query users by age in ascending and then by their name in ascending, query would look like:

Map users = await Firegraph.resolve(FirebaseFirestore.instance, r'''
query{
    users(orderBy:{
        age: "asc",
        name: "asc"
    }){
        id
        name
        age
    }
}
''');

Note that this will order by age first, and then by name

Limit queries

To limit the number of queried documents in a collection or subcollection, supply limit argument.

For example, to query only 10 users, your query would look like:

Map users = await Firegraph.resolve(FirebaseFirestore.instance, r'''
query{
    users(limit: 10){
        id
        name
        age
    }
}
''');