List Products DB calls reduced. TotalRecords variable added to Produc…

…t structure for help in same. Changes made accordingly to Filters and Search API,so this is highly unstable version. In Response.go StatusBadRequest changed to status.

db/db.go

@@ -6,7 +6,7 @@ import (
 )
 
 type Storer interface {
-	ListProducts(context.Context, int, int) (int, []Product, error)
+	ListProducts(context.Context, int, int) ([]Product, error)
 	FilteredProducts(context.Context, Filter, string, string) (int, []Product, error)
 	SearchProductsByText(context.Context, string, string, string) (int, []Product, error)
 	CreateProduct(context.Context, Product, []*multipart.FileHeader) (Product, error)

db/filters.go

@@ -193,13 +193,12 @@ func (s *pgStore) SearchProductsByText(ctx context.Context, text string, limitSt
 
 	// countResult set should have only 1 record
 	// It counts the number of records with the search results.
-	for countResult.Next() {
+	if countResult.Next() {
 		err = countResult.Scan(&totalRecords)
 		if err != nil {
 			logger.WithField("err", err.Error()).Error("Error fetching count of getSearchCount from database")
 			return 0, []Product{}, err
 		}
-		break
 	}
 
 	offset, _ := strconv.Atoi(offsetStr)

db/product.go

@@ -18,8 +18,10 @@ import (
 )
 
 const (
-	getProductCount     = `SELECT count(id) from Products ;`
-	getProductQuery     = `SELECT * FROM products p INNER JOIN category c ON p.cid = c.cid ORDER BY p.id LIMIT $1 OFFSET $2 ;`
+	getProductCount = `SELECT count(id) from Products ;`
+	getProductQuery = `SELECT count(*) OVER() AS total,* FROM products p 
+						INNER JOIN category c ON p.cid = c.cid ORDER BY p.id LIMIT $1 OFFSET $2 ;`
+	//SELECT * FROM products p INNER JOIN category c ON p.cid = c.cid ORDER BY p.id LIMIT $1 OFFSET $2 ;`
 	getProductByIDQuery = `SELECT * FROM products p INNER JOIN category c ON p.cid = c.cid WHERE p.id=$1`
 	insertProductQuery  = `INSERT INTO products ( name, description,
                  price, discount, tax, quantity, cid, brand, color, size, image_urls) VALUES ( 
@@ -28,7 +30,8 @@ const (
 	deleteProductIdQuery = `DELETE FROM products WHERE id = $1 RETURNING image_urls`
 	//updateProductStockQuery = `UPDATE products SET quantity= $1 where id = $2 `
 	updateProductStockQuery = `UPDATE products SET quantity= (quantity - $1) where id = $2 
-			RETURNING *, (SELECT cname from category where cid=(SELECT cid FROM products where id = $2))`
+				RETURNING *,(SELECT cname from category where cid=
+				(SELECT cid FROM products where id = $2))`
 	updateProductQuery = `UPDATE products SET name= :name, description=:description, price=:price, 
 					   discount=:discount, tax=:tax, quantity=:quantity, cid=:cid, brand=:brand, 
 					   color=:color, size=:size, image_urls=:image_urls WHERE id = :id
@@ -49,6 +52,7 @@ type Product struct {
 	Color        string         `db:"color" json:"color,*" schema:"color,*"`
 	Size         string         `db:"size" json:"size,*" schema:"size,*"`
 	URLs         pq.StringArray `db:"image_urls" json:"image_urls,*"  schema:"images"`
+	TotalRecords int            `db:"total" json:"-"`
 }
 
 // Pagination helps to return UI side with number of pages given a limitStr and pageStr number from Query Parameters
@@ -179,30 +183,34 @@ func (s *pgStore) GetProductByID(ctx context.Context, id int) (Product, error) {
 // @Description Get limited number of Products of particular pageStr
 // @Params req.Context , limitStr, pageStr
 // @Returns Count of Records, error if any
-func (s *pgStore) ListProducts(ctx context.Context, limit int, offset int) (int, []Product, error) {
+func (s *pgStore) ListProducts(ctx context.Context, limit int, offset int) ([]Product, error) {
 
-	var totalRecords int
 	var products []Product
 
-	err := s.db.QueryRow(getProductCount).Scan(&totalRecords)
+	result, err := s.db.Queryx(getProductQuery, limit, offset)
 	if err != nil {
-		logger.WithField("err", err.Error()).Error("Error fetching Count of Products from database")
-		return 0, []Product{}, err
+		logger.WithField("err", err.Error()).Error("Error fetching Products from database")
+		return []Product{}, err
 	}
+	for result.Next() {
+		var product Product
+		err = result.StructScan(&product)
+		if err != nil {
+			logger.WithField("err", err.Error()).Error("Error scanning Products from database")
+			return []Product{}, err
+		}
+		products = append(products, product)
+	}
+	//fmt.Println(products)
 
-	if totalRecords-1 < offset {
-		err = fmt.Errorf("Page out of Range!")
+	if len(products) > 0 && products[0].TotalRecords-1 >= offset {
+		return products, nil
+	} else {
+		err = fmt.Errorf("Page out of Range or No Records Present!")
 		logger.WithField("err", err.Error()).Error("Error Offset is greater than total records")
-		return 0, []Product{}, err
-
+		return []Product{}, err
 	}
 
-	err = s.db.Select(&products, getProductQuery, limit, offset)
-	if err != nil {
-		logger.WithField("err", err.Error()).Error("Error fetching Product Ids from database")
-		return 0, []Product{}, err
-	}
-	return totalRecords, products, nil
 }
 
 func (s *pgStore) CreateProduct(ctx context.Context, product Product, images []*multipart.FileHeader) (Product, error) {

service/filters_http.go

@@ -174,27 +174,30 @@ func getProductBySearchHandler(deps Dependencies) http.HandlerFunc {
 		offsetStr := strconv.Itoa(offset)
 		if text == "" {
 			// Behave same as List All Products and return
-			totalRecords, products, err = deps.Store.ListProducts(req.Context(), limit, offset)
-			if err != nil {
-				logger.WithField("err", err.Error()).Error("Error Fetching Product details or Page out of range")
-				Message := "Couldn't find any Product records or Page out of range"
+			products, err = deps.Store.ListProducts(req.Context(), limit, offset)
+
+			if err != nil || products[0].TotalRecords == 0 {
+				logger.WithField("err", err.Error()).Error("Error Couldn't find any Product records or Page out of range")
+				Message := "Couldn't find any Products records or Page out of range"
 				responseMsg(rw, http.StatusBadRequest, Message)
 				return
 			}
 			goto Skip
 		}
 
 		totalRecords, products, err = deps.Store.SearchProductsByText(req.Context(), text, limitStr, offsetStr)
-		if err != nil {
+		if err != nil || totalRecords == 0 {
 			logger.WithField("err", err.Error()).Error("Error Couldn't find any matching search records or Page out of range")
 			Message := "Couldn't find any matching search records or Page out of range"
 			responseMsg(rw, http.StatusBadRequest, Message)
 			return
+		} else {
+			products[0].TotalRecords = totalRecords
 		}
 
 	Skip:
 		var pagination db.Pagination
-		pagination.TotalPages = int(math.Ceil(float64(totalRecords) / float64(limit)))
+		pagination.TotalPages = int(math.Ceil(float64(products[0].TotalRecords) / float64(limit)))
 		pagination.Products = products
 		response(rw, http.StatusOK, pagination)
 		return

service/product_http.go

@@ -57,16 +57,17 @@ func listProductsHandler(deps Dependencies) http.HandlerFunc {
 			return
 		}
 		offset := (page - 1) * limit
-		totalRecords, products, err := deps.Store.ListProducts(req.Context(), limit, offset)
-		if err != nil {
+		products, err := deps.Store.ListProducts(req.Context(), limit, offset)
+
+		if err != nil || products[0].TotalRecords == 0 {
 			logger.WithField("err", err.Error()).Error("Error Couldn't find any Product records or Page out of range")
 			Message := "Couldn't find any Products records or Page out of range"
 			responseMsg(rw, http.StatusInternalServerError, Message)
 			return
 		}
 
 		var pagination db.Pagination
-		pagination.TotalPages = int(math.Ceil(float64(totalRecords) / float64(limit)))
+		pagination.TotalPages = int(math.Ceil(float64(products[0].TotalRecords) / float64(limit)))
 		pagination.Products = products
 		response(rw, http.StatusOK, pagination)
 		return

service/response.go

@@ -19,7 +19,7 @@ type messageObject struct {
 }
 
 func responseMsg(rw http.ResponseWriter, status int, msgbody string) {
-	response(rw, http.StatusBadRequest, errorResponse{
+	response(rw, status, errorResponse{
 		Error: messageObject{
 			Message: msgbody,
 		},