Golang datastore.NewQuery函數代碼示例

func ExampleQuery() {
	ctx := context.Background()
	client, err := datastore.NewClient(ctx, "project-id")
	if err != nil {
		log.Fatal(err)
	}

	// Count the number of the post entities.
	q := datastore.NewQuery("Post")
	n, err := client.Count(ctx, q)
	if err != nil {
		log.Fatal(err)
	}
	log.Printf("There are %d posts.", n)

	// List the posts published since yesterday.
	yesterday := time.Now().Add(-24 * time.Hour)
	q = datastore.NewQuery("Post").Filter("PublishedAt >", yesterday)
	it := client.Run(ctx, q)
	// Use the iterator.
	_ = it

	// Order the posts by the number of comments they have recieved.
	datastore.NewQuery("Post").Order("-Comments")

	// Start listing from an offset and limit the results.
	datastore.NewQuery("Post").Offset(20).Limit(10)
}

func ExampleQuery_kindless() {
	var lastSeenKey *datastore.Key
	// [START kindless_query]
	query := datastore.NewQuery("").Filter("__key__ >", lastSeenKey)
	// [END kindless_query]
	_ = query // Use client.Run or client.GetAll to execute the query.
}

func _getRatesKeys(r *http.Request, jsonKey []byte, unixtime int64) <-chan keyResult {
	out := make(chan keyResult)
	go func() {
		defer close(out)
		var ctx context.Context
		if r != nil {
			ctx = appengine.NewContext(r)
		} else {
			ctx = context.Background()
		}

		client, err := datastore.NewClient(ctx, "rp-optima")
		if err != nil {
			out <- keyResult{error: err}
			return
		}

		/*if keys, err := client.GetAll(ctx, datastore.NewQuery("ResultData").Filter("timestamp<", unixtime).KeysOnly(), nil); err != nil {
			out <- keyResult{error:err}
			return
		}else {
			out <- keyResult{keys:keys}
		}*/
		if keys, err := client.GetAll(ctx, datastore.NewQuery("Rate").Filter("id<", unixtime).KeysOnly(), nil); err != nil {
			out <- keyResult{error: err}
		} else {
			out <- keyResult{keys: keys}
		}
	}()
	return out
}

func ExampleNewQuery_options() {
	// Query to order the posts by the number of comments they have recieved.
	q := datastore.NewQuery("Post").Order("-Comments")
	// Start listing from an offset and limit the results.
	q = q.Offset(20).Limit(10)
	_ = q // TODO: Use the query.
}

func ExampleIterator_Cursor() {
	ctx := context.Background()
	client, _ := datastore.NewClient(ctx, "my-proj")
	cursorStr := ""
	// [START cursor_paging]
	const pageSize = 5
	query := datastore.NewQuery("Tasks").Limit(pageSize)
	if cursorStr != "" {
		cursor, err := datastore.DecodeCursor(cursorStr)
		if err != nil {
			log.Fatalf("Bad cursor %q: %v", cursorStr, err)
		}
		query = query.Start(cursor)
	}

	// Read the tasks.
	var tasks []Task
	var task Task
	it := client.Run(ctx, query)
	_, err := it.Next(&task)
	for err == nil {
		tasks = append(tasks, task)
		_, err = it.Next(&task)
	}
	if err != datastore.Done {
		log.Fatalf("Failed fetching results: %v", err)
	}

	// Get the cursor for the next page of results.
	nextCursor, err := it.Cursor()
	// [END cursor_paging]
	_ = err        // Check the error.
	_ = nextCursor // Use nextCursor.String as the next page's token.
}

func ExampleQuery_EventualConsistency() {
	// [START eventual_consistent_query]
	ancestor := datastore.NameKey("TaskList", "default", nil)
	query := datastore.NewQuery("Task").Ancestor(ancestor).EventualConsistency()
	// [END eventual_consistent_query]
	_ = query // Use client.Run or client.GetAll to execute the query.
}

func ExampleQuery_Ancestor() {
	// [START ancestor_query]
	ancestor := datastore.NameKey("TaskList", "default", nil)
	query := datastore.NewQuery("Task").Ancestor(ancestor)
	// [END ancestor_query]
	_ = query // Use client.Run or client.GetAll to execute the query.
}

func ExampleQuery_keyFilter() {
	// [START key_filter]
	key := datastore.NameKey("Task", "someTask", nil)
	query := datastore.NewQuery("Task").Filter("__key__ >", key)
	// [END key_filter]
	_ = query // Use client.Run or client.GetAll to execute the query.
}

func ExampleIterator_Cursor() {
	ctx := context.Background()
	client, err := datastore.NewClient(ctx, "project-id")
	if err != nil {
		// TODO: Handle error.
	}
	it := client.Run(ctx, datastore.NewQuery("Post"))
	for {
		var p Post
		_, err := it.Next(&p)
		if err == iterator.Done {
			break
		}
		if err != nil {
			// TODO: Handle error.
		}
		fmt.Println(p)
		cursor, err := it.Cursor()
		if err != nil {
			// TODO: Handle error.
		}
		// When printed, a cursor will display as a string that can be passed
		// to datastore.NewCursor.
		fmt.Printf("to resume with this post, use cursor %s\n", cursor)
	}
}

func ExampleQuery_keyFilter() {
	ctx := context.Background()
	// [START key_filter]
	key := datastore.NewKey(ctx, "Task", "someTask", 0, nil)
	query := datastore.NewQuery("Task").Filter("__key__ >", key)
	// [END key_filter]
	_ = query // Use client.Run or client.GetAll to execute the query.
}

func ExampleQuery_Ancestor() {
	ctx := context.Background()
	// [START ancestor_query]
	ancestor := datastore.NewKey(ctx, "TaskList", "default", 0, nil)
	query := datastore.NewQuery("Task").Ancestor(ancestor)
	// [END ancestor_query]
	_ = query // Use client.Run or client.GetAll to execute the query.
}

func ExampleQuery_Filter_arrayEquality() {
	// [START array_value_equality]
	query := datastore.NewQuery("Task").
		Filter("Tag =", "fun").
		Filter("Tag =", "programming")
	// [END array_value_equality]
	_ = query // Use client.Run or client.GetAll to execute the query.
}

func ExampleQuery_Filter_invalidInequality() {
	// [START inequality_invalid]
	query := datastore.NewQuery("Task").
		Filter("Created >", time.Date(1990, 1, 1, 0, 0, 0, 0, time.UTC)).
		Filter("Priority >", 3)
	// [END inequality_invalid]
	_ = query // The query is invalid.
}

func ExampleQuery_Filter_inequality() {
	// [START inequality_range]
	query := datastore.NewQuery("Task").
		Filter("Created >", time.Date(1990, 1, 1, 0, 0, 0, 0, time.UTC)).
		Filter("Created <", time.Date(2000, 1, 1, 0, 0, 0, 0, time.UTC))
	// [END inequality_range]
	_ = query // Use client.Run or client.GetAll to execute the query.
}

func ExampleQuery_invalidInequalitySortA() {
	// [START inequality_sort_invalid_not_same]
	query := datastore.NewQuery("Task").
		Filter("Priority >", 3).
		Order("Created")
	// [END inequality_sort_invalid_not_same]
	_ = query // The query is invalid.
}