Golang Query.Count方法代碼示例

// Count returns the number of results for the query.
func (g *Goon) Count(q *datastore.Query) (int, error) {
	return q.Count(g.Context)
}

func handler(w http.ResponseWriter, r *http.Request) {

	c := appengine.NewContext(r)
	u := user.Current(c)
	log.Infof(c, "Got a visitor to the front page!") //keep log in the imports

	//Check if the request is before or after to create the right query
	//The GET requests for the stories will be based around the SubmitDateTime
	//Using "after" will return stories after a certain date from newest to oldest
	//Using "before" will return stories before a certain date from oldest to newest
	//Default is to use the latest 3 submissions

	afterDate := r.FormValue("after")
	beforeDate := r.FormValue("before")
	returnLimit := 3
	showPrevLink := false

	var q *datastore.Query

	if afterDate != "" {
		showPrevLink = true
		//Get the results in descending order for newest to oldest
		afterDate = strings.Replace(afterDate, "%20", " ", -1) //replace all %20 with " "
		ttime, err := time.Parse(DateTimeDatastoreFormat, afterDate)
		if err != nil {
			serveError(c, w, err)
			return
		}
		q = datastore.NewQuery(WebSubmissionEntityName).
			Filter("SubmitDateTime <", ttime).
			Order("-SubmitDateTime").
			Limit(returnLimit)
	} else if beforeDate != "" {
		showPrevLink = true
		//Get the results is ascending order from oldest to newest
		beforeDate = strings.Replace(beforeDate, "%20", " ", -1) //replace all %20 with " "
		ttime, err := time.Parse(DateTimeDatastoreFormat, beforeDate)
		if err != nil {
			serveError(c, w, err)
			return
		}
		q = datastore.NewQuery(WebSubmissionEntityName).
			Filter("SubmitDateTime >", ttime).
			Order("SubmitDateTime").
			Limit(returnLimit)

		//limit check at the beginning if less than the returnLimit redo from the beginning
		length, cerr := q.Count(c)
		if cerr != nil {
			serveError(c, w, cerr)
		}

		//TODO refactor to not duplicate the default query below
		if length < returnLimit {
			showPrevLink = false
			q = datastore.NewQuery(WebSubmissionEntityName).
				Order("-SubmitDateTime").
				Limit(returnLimit)
		}
	} else {
		q = datastore.NewQuery(WebSubmissionEntityName).
			Order("-SubmitDateTime").
			Limit(returnLimit)

	}

	//Populate the results struct and store the keys
	var pageCon PageContainer

	for t := q.Run(c); ; {
		var x WebSubmission
		key, err := t.Next(&x)
		if err == datastore.Done {
			break
		}
		if err != nil {
			//			serveError(c,w,err)
			fmt.Fprintf(w, "nope %v", err.Error())
			return
		}
		if u == nil {
			pageCon.Stories = append(pageCon.Stories, StoryListData{x, key, false})
		} else {
			pageCon.Stories = append(pageCon.Stories, StoryListData{x, key, u.String() == x.SubmitBy})
		}
	}

	//if we filled up the page with results there are probably more, build the
	//next page link
	length, cerr := q.Count(c)
	if cerr != nil {
		serveError(c, w, cerr)
	}
	if length == returnLimit {
		//get the submit datetime of the last story
		pageCon.AfterLink = pageCon.Stories[returnLimit-1].Story.SubmitDateTime.Format(DateTimeDatastoreFormat)
	}

	//If it was a prev page press reverse the result array to get it back into chronological order
	if length >= 1 && beforeDate != "" {
//.........這裏部分代碼省略.........