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145 lines
4.2 KiB
Text
145 lines
4.2 KiB
Text
// Copyright 2017 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// DO NOT EDIT doc.go. Modify internal/doc.template, then run make -C internal.
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/*
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Package firestore provides a client for reading and writing to a Cloud Firestore
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database.
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See https://cloud.google.com/firestore/docs for an introduction
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to Cloud Firestore and additional help on using the Firestore API.
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Note: you can't use both Cloud Firestore and Cloud Datastore in the same
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project.
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Creating a Client
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To start working with this package, create a client with a project ID:
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[NewClient]
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CollectionRefs and DocumentRefs
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In Firestore, documents are sets of key-value pairs, and collections are groups of
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documents. A Firestore database consists of a hierarchy of alternating collections
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and documents, referred to by slash-separated paths like
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"States/California/Cities/SanFrancisco".
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This client is built around references to collections and documents. CollectionRefs
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and DocumentRefs are lightweight values that refer to the corresponding database
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entities. Creating a ref does not involve any network traffic.
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[refs]
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Reading
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Use DocumentRef.Get to read a document. The result is a DocumentSnapshot.
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Call its Data method to obtain the entire document contents as a map.
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[docref.Get]
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You can also obtain a single field with DataAt, or extract the data into a struct
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with DataTo. With the type definition
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[structDef]
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we can extract the document's data into a value of type State:
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[DataTo]
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Note that this client supports struct tags beginning with "firestore:" that work like
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the tags of the encoding/json package, letting you rename fields, ignore them, or
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omit their values when empty.
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To retrieve multiple documents from their references in a single call, use
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Client.GetAll.
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[GetAll]
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Writing
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For writing individual documents, use the methods on DocumentReference.
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Create creates a new document.
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[docref.Create]
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The first return value is a WriteResult, which contains the time
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at which the document was updated.
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Create fails if the document exists. Another method, Set, either replaces an existing
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document or creates a new one.
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[docref.Set]
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To update some fields of an existing document, use Update. It takes a list of
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paths to update and their corresponding values.
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[docref.Update]
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Use DocumentRef.Delete to delete a document.
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[docref.Delete]
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Preconditions
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You can condition Deletes or Updates on when a document was last changed. Specify
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these preconditions as an option to a Delete or Update method. The check and the
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write happen atomically with a single RPC.
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[LUT-precond]
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Here we update a doc only if it hasn't changed since we read it.
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You could also do this with a transaction.
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To perform multiple writes at once, use a WriteBatch. Its methods chain
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for convenience.
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WriteBatch.Commit sends the collected writes to the server, where they happen
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atomically.
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[WriteBatch]
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Queries
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You can use SQL to select documents from a collection. Begin with the collection, and
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build up a query using Select, Where and other methods of Query.
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[Query]
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Call the Query's Documents method to get an iterator, and use it like
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the other Google Cloud Client iterators.
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[Documents]
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To get all the documents in a collection, you can use the collection itself
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as a query.
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[CollQuery]
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Transactions
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Use a transaction to execute reads and writes atomically. All reads must happen
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before any writes. Transaction creation, commit, rollback and retry are handled for
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you by the Client.RunTransaction method; just provide a function and use the
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read and write methods of the Transaction passed to it.
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[Transaction]
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Authentication
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See examples of authorization and authentication at
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https://godoc.org/cloud.google.com/go#pkg-examples.
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*/
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package firestore
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