Optimize campaign and subscriber queries

- Simplify campaigns querying to separate statistics gather into
  a separate query for lazy loading.
- Simplify subscribers query to separate list fetching into
  a separate query for lazy loading.

campaigns.go

@@ -43,7 +43,7 @@ type campaignStats struct {
 }
 
 type campsWrap struct {
-	Results []models.Campaign `json:"results"`
+	Results models.Campaigns `json:"results"`
 
 	Query   string `json:"query"`
 	Total   int    `json:"total"`
@@ -100,6 +100,12 @@ func handleGetCampaigns(c echo.Context) error {
 		}
 	}
 
+	// Lazy load stats.
+	if err := out.Results.LoadStats(app.Queries.GetCampaignStats); err != nil {
+		return echo.NewHTTPError(http.StatusInternalServerError,
+			fmt.Sprintf("Error fetching campaign stats: %v", pqErrMsg(err)))
+	}
+
 	if single {
 		return c.JSON(http.StatusOK, okResp{out.Results[0]})
 	}
@@ -396,7 +402,7 @@ func handleGetRunningCampaignStats(c echo.Context) error {
 		out []campaignStats
 	)
 
-	if err := app.Queries.GetCampaignStats.Select(&out, models.CampaignStatusRunning); err != nil {
+	if err := app.Queries.GetCampaignStatus.Select(&out, models.CampaignStatusRunning); err != nil {
 		if err == sql.ErrNoRows {
 			return c.JSON(http.StatusOK, okResp{[]struct{}{}})
 		}

frontend/my/src/Campaigns.js

@@ -159,9 +159,9 @@ class Campaigns extends React.PureComponent {
           const out = []
           lists.forEach(l => {
             out.push(
-              <span className="name" key={`name-${l.id}`}>
+              <Tag className="name" key={`name-${l.id}`}>
                 <Link to={`/subscribers/lists/${l.id}`}>{l.name}</Link>
-              </span>
+              </Tag>
             )
           })
 

models/models.go

@@ -3,6 +3,7 @@ package models
 import (
 	"database/sql/driver"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"html/template"
 	"regexp"
@@ -90,12 +91,16 @@ type Subscriber struct {
 	Attribs     SubscriberAttribs `db:"attribs" json:"attribs"`
 	Status      string            `db:"status" json:"status"`
 	CampaignIDs pq.Int64Array     `db:"campaigns" json:"-"`
-	Lists       []List            `json:"lists"`
+	Lists       types.JSONText    `db:"lists" json:"lists"`
 
 	// Pseudofield for getting the total number of subscribers
 	// in searches and queries.
 	Total int `db:"total" json:"-"`
 }
+type subLists struct {
+	SubscriberID int            `db:"subscriber_id"`
+	Lists        types.JSONText `db:"lists"`
+}
 
 // SubscriberAttribs is the map of key:value attributes of a subscriber.
 type SubscriberAttribs map[string]interface{}
@@ -134,10 +139,7 @@ type Campaign struct {
 	Tags        pq.StringArray `db:"tags" json:"tags"`
 	TemplateID  int            `db:"template_id" json:"template_id"`
 	MessengerID string         `db:"messenger" json:"messenger"`
-	Lists       types.JSONText `db:"lists" json:"lists"`
 
-	View   int `db:"views" json:"views"`
-	Clicks int `db:"clicks" json:"clicks"`
 	// TemplateBody is joined in from templates by the next-campaigns query.
 	TemplateBody string             `db:"template_body" json:"-"`
 	Tpl          *template.Template `json:"-"`
@@ -149,12 +151,23 @@ type Campaign struct {
 
 // CampaignMeta contains fields tracking a campaign's progress.
 type CampaignMeta struct {
+	CampaignID int `db:"campaign_id" json:""`
+	Views      int `db:"views" json:"views"`
+	Clicks     int `db:"clicks" json:"clicks"`
+
+	// This is a list of {list_id, name} pairs unlike Subscriber.Lists[]
+	// because lists can be deleted after a campaign is finished, resulting
+	// in null lists data to be returned. For that reason, campaign_lists maintains
+	// campaign-list associations with a historical record of id + name that persist
+	// even after a list is deleted.
+	Lists types.JSONText `db:"lists" json:"lists"`
+
 	StartedAt null.Time `db:"started_at" json:"started_at"`
 	ToSend    int       `db:"to_send" json:"to_send"`
 	Sent      int       `db:"sent" json:"sent"`
 }
 
-// Campaigns represents a slice of Campaign.
+// Campaigns represents a slice of Campaigns.
 type Campaigns []Campaign
 
 // Media represents an uploaded media item.
@@ -179,29 +192,32 @@ type Template struct {
 	IsDefault bool   `db:"is_default" json:"is_default"`
 }
 
+// GetIDs returns the list of subscriber IDs.
+func (subs Subscribers) GetIDs() []int {
+	IDs := make([]int, len(subs))
+	for i, c := range subs {
+		IDs[i] = c.ID
+	}
+
+	return IDs
+}
+
 // LoadLists lazy loads the lists for all the subscribers
 // in the Subscribers slice and attaches them to their []Lists property.
 func (subs Subscribers) LoadLists(stmt *sqlx.Stmt) error {
-	var (
+	var sl []subLists
-		lists  []List
+	err := stmt.Select(&sl, pq.Array(subs.GetIDs()))
-		subIDs = make([]int, len(subs))
-	)
-	for i := 0; i < len(subs); i++ {
-		subIDs[i] = subs[i].ID
-		subs[i].Lists = make([]List, 0)
-	}
-
-	err := stmt.Select(&lists, pq.Array(subIDs))
 	if err != nil {
 		return err
 	}
 
-	// Loop through each list and attach it to the subscribers by ID.
+	if len(subs) != len(sl) {
-	for _, l := range lists {
+		return errors.New("campaign stats count does not match")
-		for i := 0; i < len(subs); i++ {
-			if l.SubscriberID == subs[i].ID {
-				subs[i].Lists = append(subs[i].Lists, l)
 	}
+
+	for i, s := range sl {
+		if s.SubscriberID == subs[i].ID {
+			subs[i].Lists = s.Lists
 		}
 	}
 
@@ -221,6 +237,38 @@ func (s SubscriberAttribs) Scan(src interface{}) error {
 	return fmt.Errorf("Could not not decode type %T -> %T", src, s)
 }
 
+// GetIDs returns the list of campaign IDs.
+func (camps Campaigns) GetIDs() []int {
+	IDs := make([]int, len(camps))
+	for i, c := range camps {
+		IDs[i] = c.ID
+	}
+
+	return IDs
+}
+
+// LoadStats lazy loads campaign stats onto a list of campaigns.
+func (camps Campaigns) LoadStats(stmt *sqlx.Stmt) error {
+	var meta []CampaignMeta
+	if err := stmt.Select(&meta, pq.Array(camps.GetIDs())); err != nil {
+		return err
+	}
+
+	if len(camps) != len(meta) {
+		return errors.New("campaign stats count does not match")
+	}
+
+	for i, c := range meta {
+		if c.CampaignID == camps[i].ID {
+			camps[i].Lists = c.Lists
+			camps[i].Views = c.Views
+			camps[i].Clicks = c.Clicks
+		}
+	}
+
+	return nil
+}
+
 // CompileTemplate compiles a campaign body template into its base
 // template and sets the resultant template to Campaign.Tpl.
 func (c *Campaign) CompileTemplate(f template.FuncMap) error {

queries.go

@@ -46,6 +46,7 @@ type Queries struct {
 	GetCampaign              *sqlx.Stmt `query:"get-campaign"`
 	GetCampaignForPreview    *sqlx.Stmt `query:"get-campaign-for-preview"`
 	GetCampaignStats         *sqlx.Stmt `query:"get-campaign-stats"`
+	GetCampaignStatus        *sqlx.Stmt `query:"get-campaign-status"`
 	NextCampaigns            *sqlx.Stmt `query:"next-campaigns"`
 	NextCampaignSubscribers  *sqlx.Stmt `query:"next-campaign-subscribers"`
 	GetOneCampaignSubscriber *sqlx.Stmt `query:"get-one-campaign-subscriber"`

queries.sql

@@ -9,10 +9,25 @@ SELECT * FROM subscribers WHERE CASE WHEN $1 > 0 THEN id = $1 ELSE uuid = $2 END
 SELECT * FROM subscribers WHERE email=ANY($1);
 
 -- name: get-subscriber-lists
--- Get lists belonging to subscribers.
+-- Get lists associations of subscribers given a list of subscriber IDs.
-SELECT lists.*, subscriber_lists.subscriber_id, subscriber_lists.status AS subscription_status FROM lists
+-- This query is used to lazy load given a list of subscriber IDs.
+-- The query returns results in the same order as the given subscriber IDs, and for non-existent subscriber IDs,
+-- the query still returns a row with 0 values. Thus, for lazy loading, the application simply iterate on the results in
+-- the same order as the list of campaigns it would've queried and attach the results.
+WITH subs AS (
+    SELECT subscriber_id, JSON_AGG(
+        ROW_TO_JSON(
+            (SELECT l FROM (SELECT subscriber_lists.status AS subscription_status, lists.*) l)
+        )
+    ) AS lists FROM lists
     LEFT JOIN subscriber_lists ON (subscriber_lists.list_id = lists.id)
-    WHERE subscriber_lists.subscriber_id = ANY($1::INT[]);
+    WHERE subscriber_lists.subscriber_id = ANY($1)
+    GROUP BY subscriber_id
+)
+SELECT id as subscriber_id,
+    COALESCE(s.lists, '[]') AS lists
+    FROM (SELECT id FROM UNNEST($1) AS id) x
+    LEFT JOIN subs AS s ON (s.subscriber_id = id);
 
 -- name: insert-subscriber
 WITH sub AS (
@@ -259,56 +274,42 @@ INSERT INTO campaign_lists (campaign_id, list_id, list_name)
 -- there's a COUNT() OVER() that still returns the total result count
 -- for pagination in the frontend, albeit being a field that'll repeat
 -- with every resultant row.
-WITH camps AS (
+SELECT COUNT(*) OVER () AS total, campaigns.*
-    SELECT COUNT(*) OVER () AS total, campaigns.*, (
-        SELECT COALESCE(ARRAY_TO_JSON(ARRAY_AGG(l)), '[]') FROM (
-            SELECT COALESCE(campaign_lists.list_id, 0) AS id,
-            campaign_lists.list_name AS name
-            FROM campaign_lists WHERE campaign_lists.campaign_id = campaigns.id
-        ) l
-    ) AS lists
 FROM campaigns
 WHERE ($1 = 0 OR id = $1)
     AND status=ANY(CASE WHEN ARRAY_LENGTH($2::campaign_status[], 1) != 0 THEN $2::campaign_status[] ELSE ARRAY[status] END)
     AND ($3 = '' OR (to_tsvector(name || subject) @@ to_tsquery($3)))
-    ORDER BY created_at DESC OFFSET $4 LIMIT $5
+ORDER BY created_at DESC OFFSET $4 LIMIT $5;
-), views AS (
-    SELECT campaign_id, COUNT(campaign_id) as num FROM campaign_views
-    WHERE campaign_id = ANY(SELECT id FROM camps)
-    GROUP BY campaign_id
-),
-clicks AS (
-    SELECT campaign_id, COUNT(campaign_id) as num FROM link_clicks
-    WHERE campaign_id = ANY(SELECT id FROM camps)
-    GROUP BY campaign_id
-)
-SELECT *,
-    COALESCE(v.num, 0) AS views,
-    COALESCE(c.num, 0) AS clicks
-FROM camps
-LEFT JOIN views AS v ON (v.campaign_id = camps.id)
-LEFT JOIN clicks AS c ON (c.campaign_id = camps.id)
-ORDER BY camps.created_at DESC;
 
 -- name: get-campaign
-WITH camp AS (
+SELECT * FROM campaigns WHERE id = $1;
-    SELECT * FROM campaigns WHERE id = $1
+
+-- name: get-campaign-stats
+-- This query is used to lazy load campaign stats (views, counts, list of lists) given a list of campaign IDs.
+-- The query returns results in the same order as the given campaign IDs, and for non-existent campaign IDs,
+-- the query still returns a row with 0 values. Thus, for lazy loading, the application simply iterate on the results in
+-- the same order as the list of campaigns it would've queried and attach the results.
+WITH lists AS (
+    SELECT campaign_id, JSON_AGG(JSON_BUILD_OBJECT('id', list_id, 'name', list_name)) AS lists FROM campaign_lists
+    WHERE campaign_id = ANY($1) GROUP BY campaign_id
 ), views AS (
     SELECT campaign_id, COUNT(campaign_id) as num FROM campaign_views
-    WHERE campaign_id = ANY(SELECT id FROM camp)
+    WHERE campaign_id = ANY($1)
     GROUP BY campaign_id
 ),
 clicks AS (
     SELECT campaign_id, COUNT(campaign_id) as num FROM link_clicks
-    WHERE campaign_id = ANY(SELECT id FROM camp)
+    WHERE campaign_id = ANY($1)
     GROUP BY campaign_id
 )
-SELECT *,
+SELECT id as campaign_id,
     COALESCE(v.num, 0) AS views,
-    COALESCE(c.num, 0) AS clicks
+    COALESCE(c.num, 0) AS clicks,
-FROM camp
+    COALESCE(l.lists, '[]') AS lists
-LEFT JOIN views AS v ON (v.campaign_id = camp.id)
+FROM (SELECT id FROM UNNEST($1) AS id) x
-LEFT JOIN clicks AS c ON (c.campaign_id = camp.id);
+LEFT JOIN lists AS l ON (l.campaign_id = id)
+LEFT JOIN views AS v ON (v.campaign_id = id)
+LEFT JOIN clicks AS c ON (c.campaign_id = id);
 
 -- name: get-campaign-for-preview
 SELECT campaigns.*, COALESCE(templates.body, (SELECT body FROM templates WHERE is_default = true LIMIT 1)) AS template_body,
@@ -323,7 +324,7 @@ FROM campaigns
 LEFT JOIN templates ON (templates.id = campaigns.template_id)
 WHERE campaigns.id = $1;
 
--- name: get-campaign-stats
+-- name: get-campaign-status
 SELECT id, status, to_send, sent, started_at, updated_at
     FROM campaigns
     WHERE status=$1;