Transaction
A reference to a transaction.
The Transaction object passed to a transaction's updateFunction provides the methods to read and write data within the transaction context. See runTransaction().
Methods
create
create(documentRef, data) returns Transaction
Create the document referred to by the provided DocumentReference. The operation will fail the transaction if a document exists at the specified location.
Parameter |
|
---|---|
documentRef |
A reference to the document to be created. |
data |
The object data to serialize as the document. |
- Returns
-
This Transaction instance. Used for chaining method calls.
Example
firestore.runTransaction(transaction => {
let documentRef = firestore.doc('col/doc');
return transaction.get(documentRef).then(doc => {
if (!doc.exists) {
transaction.create(documentRef, { foo: 'bar' });
}
});
});
delete
delete(documentRef, precondition) returns Transaction
Deletes the document referred to by the provided [DocumentReference] DocumentReference.
Parameter |
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---|---|---|---|---|---|
documentRef |
A reference to the document to be deleted. |
||||
precondition |
Optional A precondition to enforce for this delete. Values in
|
- Returns
-
This Transaction instance. Used for chaining method calls.
Example
firestore.runTransaction(transaction => {
let documentRef = firestore.doc('col/doc');
transaction.delete(documentRef);
return Promise.resolve();
});
get
get(refOrQuery) returns Promise
Retrieve a document or a query result from the database. Holds a pessimistic lock on all returned documents.
Parameter |
|
---|---|
refOrQuery |
(DocumentReference or Query) The document or query to return. |
- Returns
-
Promise
A Promise that resolves with a DocumentSnapshot or QuerySnapshot for the returned documents.
Example
firestore.runTransaction(transaction => {
let documentRef = firestore.doc('col/doc');
return transaction.get(documentRef).then(doc => {
if (doc.exists) {
transaction.update(documentRef, { count: doc.get('count') + 1 });
} else {
transaction.create(documentRef, { count: 1 });
}
});
});
getAll
getAll(...documents) returns Promise containing Array of DocumentSnapshot
Retrieves multiple documents from Firestore. Holds a pessimistic lock on all returned documents.
Parameter |
|
---|---|
documents |
The document references to receive. Value may be repeated. |
- Returns
-
Promise containing Array of DocumentSnapshot
A Promise that contains an array with the resulting document snapshots.
Example
let firstDoc = firestore.doc('col/doc1');
let secondDoc = firestore.doc('col/doc2');
let resultDoc = firestore.doc('col/doc3');
firestore.runTransaction(transaction => {
return transaction.getAll(firstDoc, secondDoc).then(docs => {
transaction.set(resultDoc, {
sum: docs[1].get('count') + docs[2].get('count')
});
});
});
set
set(documentRef, data, options) returns Transaction
Writes to the document referred to by the provided DocumentReference. If the document does not exist yet, it will be created. If you pass SetOptions, the provided data can be merged into the existing document.
Parameter |
|||||||
---|---|---|---|---|---|---|---|
documentRef |
A reference to the document to be set. |
||||||
data |
The object to serialize as the document. |
||||||
options |
Optional An object to configure the set behavior. Values in
|
- Returns
-
This Transaction instance. Used for chaining method calls.
Example
firestore.runTransaction(transaction => {
let documentRef = firestore.doc('col/doc');
transaction.set(documentRef, { foo: 'bar' });
return Promise.resolve();
});
update
update(documentRef, dataOrField, ...preconditionOrValues) returns Transaction
Updates fields in the document referred to by the provided DocumentReference. The update will fail if applied to a document that does not exist.
The update() method accepts either an object with field paths encoded as keys and field values encoded as values, or a variable number of arguments that alternate between field paths and field values. Nested fields can be updated by providing dot-separated field path strings or by providing FieldPath objects.
A Precondition restricting this update can be specified as the last argument.
Parameter |
|
---|---|
documentRef |
A reference to the document to be updated. |
dataOrField |
(UpdateData, string, or FieldPath) An object containing the fields and values with which to update the document or the path of the first field to update. |
preconditionOrValues |
(Precondition, any type, string, or FieldPath) An alternating list of field paths and values to update or a Precondition to to enforce on this update. Value may be repeated. |
- Returns
-
This Transaction instance. Used for chaining method calls.
Example
firestore.runTransaction(transaction => {
let documentRef = firestore.doc('col/doc');
return transaction.get(documentRef).then(doc => {
if (doc.exists) {
transaction.update(documentRef, { count: doc.get('count') + 1 });
} else {
transaction.create(documentRef, { count: 1 });
}
});
});