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Chapter 08 · Firebase Firestore
Subchapter 8.12
references/standard/indexes.mdMarkdown4 KBView on GitHub
Indexes allow Firestore to ensure that query performance depends on the size of the result set, not the size of the database.
In Standard Edition, Firestore automatically creates a single-field index
for every field in a document (and subfields in maps). * Support: Simple
equality queries (==) and single-field range/sort queries (<, <=,
orderBy). * Behavior: You generally don’t need to manage these unless you
want to exempt a field.
A composite index stores a sorted mapping of all documents based on an ordered list of fields. * Support: Complex queries that filter or sort by multiple fields. * Creation: These are NOT automatically created. You must define them manually or via the console/CLI.
where("state", "==", "CA").where("country", "==", "USA")).If you attempt a query that requires a composite index, the SDK will throw an error containing a direct link to the Firebase Console to create that specific index.
Example Error:
“The query requires an index. You can create it here: https://console.firebase.google.com/project/ (opens in a new tab)…”
| Query Type | Index Required |
|---|---|
| Simple Equality`where(“a”, | Automatic (Single-Field) |
| : “==”, 1)` : : | |
| Simple Range/Sort`where(“a”, | Automatic (Single-Field) |
| : “>”, 1).orderBy(“a”)` : : | |
| Multiple Equality`where(“a”, | Automatic (Merged Single-Field) |
| : “==”, 1).where(“b”, “==”, 2)` : : | |
| **Equality + | Composite Index |
| : Range/Sort**`where(“a”, “==”, : : | |
| : 1).where(“b”, “>”, 2)` : : | |
| Multiple Ranges`where(“a”, | Composite Index (and technically |
| : “>”, 1).where(“b”, “>”, 2)` : limited query support) : | |
| **Array Contains + | Composite Index |
| : Equality**`where(“tags”, : : | |
| : “array-contains”, : : | |
| : “news”).where(“active”, “==”, true)` : : |
You can exempt fields from automatic indexing to save storage or strictly enforce write limits.
timestamp)
limits the write rate to ~500 writes/second per collection.Your indexes should be defined in firestore.indexes.json (pointed to by
firebase.json).
{
"indexes": [
{
"collectionGroup": "cities",
"queryScope": "COLLECTION",
"fields": [
{ "fieldPath": "country", "order": "ASCENDING" },
{ "fieldPath": "population", "order": "DESCENDING" }
]
}
],
"fieldOverrides": []
}Deploy indexes only:
bash npx -y firebase-tools@latest deploy --only firestore:indexes