Ordering and Limiting

Table of contents

1. Order and limit data
2. Sub collection
   1. Example Usage

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FireO provides powerful query functionality for specifying which documents you want to retrieve from a collection. These queries can also be used with either get() or fetch()

Order and limit data

By default, a query retrieves all documents that satisfy the query in ascending order by document ID. You can specify the sort order for your data using order(), and you can limit the number of documents retrieved using limit() or passing number of documents in fetch(limit).

For example, you could query for the first 3 cities alphabetically with:

City.collection.order('name').limit(3).fetch()

# Same thing can be achieved by passing limit in fetch() method
City.collection.order('name').fetch(3)

You could also sort in descending order to get the last 3 cities:

City.collection.order('-name').fetch(3)

You can also order by multiple fields. For example, if you wanted to order by state, and within each state order by population in descending order:

City.collection.order('state').order('-population')

You can combine filter() with order() and limit(). In the following example, the queries define a population threshold, sort by population in ascending order, and return only the first few results that exceed the threshold:

City.collection.filter('population', '>', 2500000).order('population').limit(2).fetch()

However, if you have a filter with a range comparison (<, <=, >, >=), your first ordering must be on the same field:

Valid: Range filter and orderBy on the same field

City.collection.filter('population', '>', 2500000).order('population').fetch()

Invalid: Range filter and first orderBy on different fields

City.collection.filter('population', '>', 2500000).order('country')

Sub collection

Sub collection queries work in same fashion but you need to pass parent_key to search in specific collection. Ordering and limiting apply same like other root collection

Sample Data

class Post(Model):
    title = TextField()
    content = TextField()


class Review(Model):
    name = TextField()
    stars = NumberField()


p = Post(title="First Post", content="Some Content")
p.save()

r1 = Review(parent=p.key)
r1.name = 'Azeem'
r1.stars = 5
r1.save()

r2 = Review(parent=p.key)
r2.name = 'Arfan'
r2.stars = 3
r2.save()

Example Usage

The following query returns all reviews order by review stars

reviews = Review.collection.parent(post_key).order('stars').fetch()