Filtering

Filtering

FastGQL extends the GraphQL schema adding filter input for objects and adding filter arguments to the queries and mutations. We can use the filter argument in our queries to filter results based on the field’s values. FastGQL allows to add multiple filters with AND, OR, NOT and even nested object filters.

Simple Operators

fetch posts with where id == 3

query {
  posts(limit: 3, filter: { id: { eq: 3 } }) {
    id
  }
}

Logical filters

AND filter

By default, a logical AND operation is preformed on all the conditions mentioned in the filter clause. If we want to use the same field key, than we need to use the AND operator in the GraphQL query.

Single

query {
    # expected filter: name = "article 1" AND id = 1
    posts(filter: {name: {eq: "article 1"}, id: {eq: 1}}) {
        id
        name
    }
}

Multiple

query {
    # expected filter: name = "article 1" AND name like "%article%" AND id = 1
    posts(filter: { AND: [ {name: {eq: "article 1"}}, {name: {like: "%article%"}}, {id: {eq: 1}}]}) {
        id
        name
    }
}

OR filter

To perform a logical OR operation, we have to use the OR operator in the GraphQL query.

If we would like to fetch information of all post’s name that start with the prefix a or b the following query will return the desired result:

query {
    posts(
        filter: { OR: [{ name: { prefix: "a" } }, { name: { suffix: "b" } }] }
    ) {
        id
        name
    }
}

NOT filter

To perform a logical NOToperation, we have to use the NOToperator in the GraphQL query.

if we would like to fetch information of all post’s name that don’t start with “a” or ends with “b”. the following query will return the desired result:

query {
    posts(
        filter: {
            NOT: { OR: [{ name: { prefix: "a" } }, { name: { suffix: "b" } }] }
        }
    ) {
        id
        name
    }
}

Nested filters

We can also perform complex nested logical operation, such as OR inside an AND operator. The following query will result the following filter:

(name like 'b%' OR name like 'a%') AND name like '%c%'

query {
    posts(
        filter: {
            AND: [
                { OR: [{ name: { prefix: "a" } }, { name: { suffix: "b" } }] }
                { name: { like: "%c%" } }
            ]
        }
    ) {
        id
        name
    }
}

Object Filters

Most objects in our schema usually have fields that aren’t scalars, and we would like to filter by thier fields. In our example each post has one or more categories we would want to filter posts by some category name. The following GraphQL query will filter for us those posts that have a category name called “Security”

query ObjectFilterExample {
    posts(filter: {categories: {name: {eq: "Security"}}}) {
        id
        name
    }
}