Saving Data on Android

Ordering and limi/ng
You've already seen how you can specify which documents you want to fetch from 
the collection by using 
whereEqualTo()
. But there's much more you can do, on top 
of the 
whereEqualTo()
:
• You can use 
orderBy()
 on the collection reference to sort the data by the specified 
field. By default, the documents are sorted in ascending order by document ID.
• You can use 
limit()
 on the collection reference to only return up to the specified 
number of documents.
• You can also combine all of the 
where
 methods for filtering with 
limit()
 and 
orderBy()
.
Pagina/on
You can have a lot of data stored in your database, but you probably don't need all of 
the data all the time. Pagination allows you to split your database data into chunks 
so that you don't need to fetch all of it at once.
Firestore provides you with the 
pagination
 feature, that works in a way where you 
don't need to execute one large query, but instead multiple smaller queries 
sequentially
. Firestores library has some useful methods that you can use to divide 
your query into smaller queries, like 
startAt()
, 
startAfter()
, 
endAt()
 or 
endBefore()
.
Check the official 
documentation
 to learn more about pagination.
Indexing
To ensure good performance for every query, Firestore requires an index. Firestore 
automatically creates indices for the basic queries for you.
Check the official 
documentation
 to learn more about how to add indexing manually 
and how it works.