From 57d115ad65e899ff15fa1204133fd79639d0d6d3 Mon Sep 17 00:00:00 2001
From: Garrett Ladley <92384606+garrettladley@users.noreply.github.com>
Date: Wed, 12 Jun 2024 22:02:37 -0400
Subject: [PATCH] =?UTF-8?q?=F0=9F=93=9D=20feat:=20optimize=20event=20previ?=
 =?UTF-8?q?ew=20query=20(#1022)?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 backend/entities/events/previews/service.go   |  2 +-
 .../entities/events/previews/transactions.go  | 66 +++++++++++++------
 backend/entities/events/tags/transactions.go  | 12 +---
 3 files changed, 50 insertions(+), 30 deletions(-)

diff --git a/backend/entities/events/previews/service.go b/backend/entities/events/previews/service.go
index b3eba712..f93f5ff9 100644
--- a/backend/entities/events/previews/service.go
+++ b/backend/entities/events/previews/service.go
@@ -22,7 +22,7 @@ func NewService(serviceParams types.ServiceParams) Service {
 
 func (h *Handler) GetEventPreviews(pageInfo *fiberpaginate.PageInfo, start string, end string) ([]EventPreview, error) {
 	if start == "" || end == "" {
-		return GetEventPreivews(h.DB, pageInfo)
+		return GetEventPreviews(h.DB, pageInfo)
 	}
 
 	startTime, err := utilities.ParseTime(start, utilities.YYYY_dash_MM_dash_DD)
diff --git a/backend/entities/events/previews/transactions.go b/backend/entities/events/previews/transactions.go
index 1c2636b6..8f257286 100644
--- a/backend/entities/events/previews/transactions.go
+++ b/backend/entities/events/previews/transactions.go
@@ -4,16 +4,16 @@ import (
 	"time"
 
 	"github.com/garrettladley/fiberpaginate"
+	"github.com/google/uuid"
 
 	"github.com/GenerateNU/sac/backend/database/cache"
-	"github.com/GenerateNU/sac/backend/entities/clubs"
-	"github.com/GenerateNU/sac/backend/entities/events/tags"
+	"github.com/GenerateNU/sac/backend/entities/models"
 	"github.com/GenerateNU/sac/backend/utilities"
 
 	"gorm.io/gorm"
 )
 
-func GetEventPreivews(db *gorm.DB, pageInfo *fiberpaginate.PageInfo) ([]EventPreview, error) {
+func GetEventPreviews(db *gorm.DB, pageInfo *fiberpaginate.PageInfo) ([]EventPreview, error) {
 	db = cache.SetUseCache(db, true)
 
 	var events []EventStub
@@ -24,19 +24,16 @@ func GetEventPreivews(db *gorm.DB, pageInfo *fiberpaginate.PageInfo) ([]EventPre
 	return processEventStubs(db, events)
 }
 
-func GetEventPreviewsByTime(db *gorm.DB, pageInfo *fiberpaginate.PageInfo, startTime *time.Time, endTime *time.Time) ([]EventPreview, error) {
-	var events []EventStub
+func GetEventPreviewsByTime(db *gorm.DB, pageInfo *fiberpaginate.PageInfo, startTime, endTime *time.Time) ([]EventPreview, error) {
+	db = cache.SetUseCache(db, true)
 
-	query := cache.SetUseCache(db, true).Model(&events)
+	var events []EventStub
+	query := db.Model(&events).Scopes(utilities.IntoScope(*pageInfo, db))
 
 	if startTime != nil && endTime != nil {
 		query = query.Where("start_time >= ? AND end_time <= ?", *startTime, *endTime)
 	}
 
-	if pageInfo != nil {
-		query = query.Scopes(utilities.IntoScope(*pageInfo, db))
-	}
-
 	if err := query.Find(&events).Error; err != nil {
 		return nil, err
 	}
@@ -45,19 +42,48 @@ func GetEventPreviewsByTime(db *gorm.DB, pageInfo *fiberpaginate.PageInfo, start
 }
 
 func processEventStubs(db *gorm.DB, events []EventStub) ([]EventPreview, error) {
-	eventPreviews := make([]EventPreview, len(events))
+	eventIDs := make([]uuid.UUID, len(events))
 	for index, event := range events {
-		eventTags, err := tags.GetEventTags(db, event.ID)
-		if err != nil {
-			return nil, err
-		}
+		eventIDs[index] = event.ID
+	}
+
+	var eventTags []struct {
+		EventID uuid.UUID `gorm:"column:event_id"`
+		TagID   uuid.UUID `gorm:"column:tag_id"`
+		Name    string    `gorm:"column:name"`
+	}
+	if err := db.Table("tags").Select("tags.id as tag_id, tags.name, event_tags.event_id").
+		Joins("JOIN event_tags ON event_tags.tag_id = tags.id").
+		Where("event_tags.event_id IN ?", eventIDs).
+		Scan(&eventTags).Error; err != nil {
+		return nil, err
+	}
+
+	eventTagsMap := make(map[uuid.UUID][]models.Tag)
+	for _, et := range eventTags {
+		eventTagsMap[et.EventID] = append(eventTagsMap[et.EventID],
+			models.Tag{
+				Model: models.Model{
+					ID: et.TagID,
+				},
+				Name: et.Name,
+			})
+	}
+
+	var hosts []models.Club
+	if err := db.Where("id IN ?", eventIDs).Find(&hosts).Error; err != nil {
+		return nil, err
+	}
 
-		host, err := clubs.GetClub(db, event.Host)
-		if err != nil {
-			return nil, err
-		}
+	hostsMap := make(map[uuid.UUID]models.Club)
+	for _, host := range hosts {
+		hostsMap[host.ID] = host
+	}
 
-		eventPreviews[index] = *event.Into(eventTags, host.Name, host.Logo)
+	eventPreviews := make([]EventPreview, len(events))
+	for index, event := range events {
+		eventPreviews[index] = *event.Into(eventTagsMap[event.ID], hostsMap[event.Host].Name, hostsMap[event.Host].Logo)
 	}
+
 	return eventPreviews, nil
 }
diff --git a/backend/entities/events/tags/transactions.go b/backend/entities/events/tags/transactions.go
index f1cf497b..d80bda35 100644
--- a/backend/entities/events/tags/transactions.go
+++ b/backend/entities/events/tags/transactions.go
@@ -1,7 +1,6 @@
 package tags
 
 import (
-	"github.com/GenerateNU/sac/backend/database/cache"
 	"github.com/GenerateNU/sac/backend/entities/events"
 
 	"github.com/GenerateNU/sac/backend/entities/models"
@@ -26,15 +25,10 @@ func CreateEventTags(db *gorm.DB, id uuid.UUID, tags []models.Tag) ([]models.Tag
 }
 
 func GetEventTags(db *gorm.DB, id uuid.UUID) ([]models.Tag, error) {
-	db = cache.SetUseCache(db, true)
-
 	var tags []models.Tag
-	event, err := events.GetEvent(db, id, transactions.PreloadTag())
-	if err != nil {
-		return nil, err
-	}
-
-	if err := db.Model(&event).Association("Tag").Find(&tags); err != nil {
+	if err := db.Joins("JOIN event_tags ON event_tags.tag_id = tags.id").
+		Where("event_tags.event_id = ?", id).
+		Find(&tags).Error; err != nil {
 		return nil, err
 	}
 	return tags, nil