Query optimization in Firebase - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a Firestore query that orders documents by the 'timestamp' field.

Firebase

const query = firestore.collection('messages').orderBy('[1]');

Drag options to blanks, or click blank then click option'

Atimestamp

Bname

Cage

Demail

Attempts:

3 left

💡 Hint

Common Mistakes

Using a field that does not exist in the collection.

Forgetting to specify the field name as a string.

The 'orderBy' method requires the field name to sort documents. Here, 'timestamp' is the correct field to order messages by time.

2fill in blank

medium

Complete the code to limit the number of documents returned by the query to 10.

Firebase

const limitedQuery = query.[1](10);

Drag options to blanks, or click blank then click option'

Afilter

BstartAt

CorderBy

Dlimit

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'filter' instead of 'limit' to restrict results.

Confusing 'orderBy' with limiting results.

The 'limit' method restricts the number of documents returned by the query. Here, it limits to 10 documents.

3fill in blank

hard

Fix the error in the query to filter documents where 'status' equals 'active'.

Firebase

const activeQuery = firestore.collection('users').where('status', '[1]', 'active');

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A==

B=

Cis

Dequals

Attempts:

3 left

💡 Hint

Common Mistakes

Using '=' instead of '==' in the where clause.

Using non-supported operators like 'equals' or 'is'.

Firestore uses '==' as the operator for equality in queries. '=' is not valid here.

4fill in blank

hard

Fill both blanks to create a query that filters documents where 'age' is greater than 18 and orders by 'age'.

Firebase

const adultQuery = firestore.collection('users').where('age', '[1]', 18).[2]('age');

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A>

B<

CorderBy

Dlimit

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' for filtering ages.

Using 'limit' instead of 'orderBy' to sort results.

The 'where' clause uses '>' to filter ages greater than 18, and 'orderBy' sorts the results by age.

5fill in blank

hard

Fill all three blanks to create a query that filters documents where 'score' is at least 50, orders by 'score', and limits results to 5.

Firebase

const topScores = firestore.collection('games').where('score', '[1]', 50).[2]('score').[3](5);

Drag options to blanks, or click blank then click option'

A>=

BorderBy

Climit

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' instead of '>=' for filtering scores.

Mixing up the order of 'orderBy' and 'limit' methods.

The query filters scores greater or equal to 50 using '>='. It orders by 'score' and limits results to 5 documents.