In and not-in queries in Firebase - Step-by-Step Execution

Process Flow - In and not-in queries

Start Query

↓

Check Query Type

↓

in query

↓

Match docs

↓

Return docs

↓

End

The query starts by checking if it is an 'in' or 'not-in' query, then matches or excludes documents accordingly, and finally returns the results.

Execution Sample

Firebase

db.collection('users')
  .where('status', 'in', ['active', 'pending'])
  .get()
  .then(snapshot => {
    // process docs
  })

This code queries the 'users' collection for documents where the 'status' field is either 'active' or 'pending'.

Process Table

Step	Query Type	Field	Operator	Values	Action	Result
1	in	status	in	['active', 'pending']	Check each doc's status	Match docs with status 'active' or 'pending'
2	in	status	in	['active', 'pending']	Collect matched docs	Docs with status 'active' or 'pending' collected
3	not-in	status	not-in	['inactive', 'banned']	Check each doc's status	Exclude docs with status 'inactive' or 'banned'
4	not-in	status	not-in	['inactive', 'banned']	Collect remaining docs	Docs without status 'inactive' or 'banned' collected
5	end	-	-	-	Return final docs	Query complete, results returned

💡 Query ends after collecting matching or excluding documents based on 'in' or 'not-in' operator.

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	Final
matchedDocs	[]	['doc1', 'doc3']	['doc1', 'doc3']	-	-	['doc1', 'doc3']
excludedDocs	[]	-	-	['doc2', 'doc4']	['doc2', 'doc4']	['doc2', 'doc4']
finalDocs	[]	-	-	-	-	['doc1', 'doc3'] or ['doc1', 'doc3', 'doc5'] depending on query

Key Moments - 3 Insights

Why does the 'in' query only return documents with specific values?

Because in step 1 and 2 of the execution_table, the query checks each document's field and only collects those matching the listed values.

How does the 'not-in' query exclude documents?

As shown in steps 3 and 4, the query checks each document and excludes those with values in the 'not-in' list, collecting only the rest.

Can 'in' and 'not-in' queries be combined in one query?

No, Firebase queries allow only one 'in' or 'not-in' filter per query, so you must run separate queries or restructure your data.

Visual Quiz - 3 Questions

Look at the execution_table, what documents are collected after step 2 in an 'in' query?

A Documents with status 'active' or 'pending'

B Documents with status 'inactive' or 'banned'

C All documents in the collection

D No documents

💡 Hint

Refer to row 2 in execution_table where matched docs are collected for 'in' query.

At which step does the 'not-in' query exclude documents with certain statuses?

A Step 1

B Step 3

C Step 5

D Step 2

💡 Hint

Check step 3 in execution_table where exclusion happens for 'not-in' query.

If you add 'inactive' to the 'in' query values, how does the matchedDocs variable change after step 2?

A It excludes documents with status 'inactive'

B It remains the same

C It includes documents with status 'inactive' as well

D It becomes empty

💡 Hint

Look at variable_tracker matchedDocs after step 2 and consider adding 'inactive' to the 'in' values.

Concept Snapshot

Firebase 'in' and 'not-in' queries filter documents by matching or excluding specific field values.
Use 'in' to get docs with any value in a list.
Use 'not-in' to exclude docs with values in a list.
Only one 'in' or 'not-in' filter per query is allowed.
Results are returned after filtering documents accordingly.

Full Transcript

This visual execution shows how Firebase 'in' and 'not-in' queries work step-by-step. The query starts by checking if it is an 'in' or 'not-in' query. For 'in' queries, it checks each document's field and collects those matching any value in the list. For 'not-in' queries, it excludes documents with values in the list and collects the rest. Variables track matched and excluded documents after each step. The query ends by returning the filtered documents. Key points include understanding how documents are matched or excluded and that only one 'in' or 'not-in' filter can be used per query. The quiz tests understanding of which documents are collected or excluded at specific steps and how changing values affects results.