Create paging filters using golang for MongoDB-Golang-php.cn

使用 golang for MongoDB 创建分页过滤器

Question content

I have a large filter and I will provide a snippet of it. I'm trying to pass a map of the paganization filter but getting the error message

the match filter must be an expression in an object

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Get filter

func (app *courses) getfilter(filter *filter) ([]bson.m, error) { pipeline := make([]bson.m, 0) if filter.all { // include all items } else { // filter items based on the provided criteria if filter.beginner { pipeline = append(pipeline, bson.m{"tags": "beginner"}) } if filter.advanced { pipeline = append(pipeline, bson.m{"tags": "advanced"}) } if filter.go { pipeline = append(pipeline, bson.m{"tags": "go"}) } } return pipeline, nil }

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Handler

func (app *courses) coursesallhandler(w http.responsewriter, r *http.request) { ctx := context.background() clog := log.getloggerfromcontext(ctx) p := r.url.query().get("page") ps := r.url.query().get("pagesize") var filter filter err := json.newdecoder(r.body).decode(&filter) if err != nil { http.error(w, "failed to parse request body", http.statusbadrequest) return } pipeline := make([]bson.m, 0) page, _ := strconv.atoi(p) pagesize, _ := strconv.atoi(ps) // pagination skip := (page - 1) * pagesize limit := pagesize // add filter pipeline, err = app.getfilter(&filter) if err != nil { clog.error(err) } pipeline = append(pipeline, bson.m{"$match": pipeline}) // add pagination stages to the pipeline pipeline = append(pipeline, bson.m{"$skip": skip}) pipeline = append(pipeline, bson.m{"$limit": limit}) res, err := app.repo.getall(ctx, pipeline) if err != nil { clog.error(err) return } err = app.helper.writejson(w, http.statusok, envelope{"data": res, "metadata": "none"}, nil) if err != nil { clog.errorctx(err, log.ctx{ "header": w.header(), "request_url": r.url.string(), }) } }

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How do I get the values set to "true" or "false", put them into a map and submit them in a query to match the database, like I'm trying to do here.

// add filter pipeline, err = app.getfilter(&filter) if err != nil { clog.error(err) } pipeline = append(pipeline, bson.m{"$match": pipeline})

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----renew----

I now have:

func (app *courses) coursesallhandler(w http.responsewriter, r *http.request) { ctx := context.background() clog := log.getloggerfromcontext(ctx) var filter filter err := json.newdecoder(r.body).decode(&filter) if err != nil { http.error(w, "failed to parse request body", http.statusbadrequest) return } filter.all = true pipeline := make([]bson.m, 3) // add filter matches, err := app.getfilter(&filter) if err != nil { clog.error(err) } pipeline[0] = bson.m{"$skip": 1} pipeline[1] = bson.m{"$limit": 5} pipeline[2] = bson.m{"$match": matches} res, err := app.repo.getall(ctx, pipeline) if err != nil { clog.error(err) return } err = app.helper.writejson(w, http.statusok, envelope{"data": res, "metadata": "none"}, nil) if err != nil { clog.errorctx(err, log.ctx{ "header": w.header(), "request_url": r.url.string(), }) } }

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The filter looks like

func (app *courses) getfilter(filter *filter) (bson.m, error) { match := bson.m{} tags := []string{} if filter.all { // include all items tags = append(tags, "beginner") tags = append(tags, "intermediate") ..... } else { // filter items based on the provided criteria if filter.beginner { tags = append(tags, "beginner") } if filter.advanced { tags = append(tags, "advanced") } if filter.go { tags = append(tags, "go") } ........ } match = bson.m{ "tags": bson.m{"$in": tags}, } return match, nil }

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Will be used here later..

func (r *CourseRepo) GetAll(ctx context.Context, pipeline []bson.M) ([]Course, error) { clog := log.GetLoggerFromContext(ctx) cur, err := r.collection.Aggregate(ctx, pipeline) ...

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But it is empty. Everything in the filter is selected, no errors.

Correct answer

Thematch filter you get must be an expression in the objectbecause$matchrequires an object (bson.m), but you have been given aslice object ([]bson.m).

Try this

func (app *Courses) getFilter(filter *Filter) (bson.M, error) { match := bson.M{} tags := []string{} if filter.All { // Include all items } else { // Filter items based on the provided criteria if filter.Beginner { tags = append(tags, "beginner") } if filter.Advanced { tags = append(tags, "advanced") } if filter.Go { tags = append(tags, "go") } match = bson.M{ "tags": bson.M{"$in": tags}, } } return match, nil }

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