[MM-45444] Denormalize Reactions to add ChannelId for top reactions insights query (#20572)

* Denormalize Reactions to add ChannelId for top reactions insights query

* Remove hardcoded timestamps

* Fix store, api4 tests for reactions

* Fix tests

* Fix integrity tests, allow reaction to have ChannelId populated before calling store function

* Lint fixes

* Add ChannelId field to BulkGetForPosts, Delete store handlers

* Add index to mysql migration, add not null characteristic without a separate command

* Select channelId instead of fetching post via store.GetPost, add if exists to drop column

* Make updating of Reactions conditional to support pre-migration

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

store/storetest/reaction_store.go

@@ -52,6 +52,7 @@ func testReactionSave(t *testing.T, ss store.Store) {
 	assert.Equal(t, saved.PostId, reaction1.PostId, "should've saved reaction post_id and returned it")
 	assert.Equal(t, saved.EmojiName, reaction1.EmojiName, "should've saved reaction emoji_name and returned it")
 	assert.NotZero(t, saved.UpdateAt, "should've saved reaction update_at and returned it")
+	assert.Equal(t, saved.ChannelId, post.ChannelId, "should've saved reaction update_at and returned it")
 	assert.Zero(t, saved.DeleteAt, "should've saved reaction delete_at with zero value and returned it")
 
 	var secondUpdateAt int64
@@ -85,9 +86,16 @@ func testReactionSave(t *testing.T, ss store.Store) {
 	assert.NotEqual(t, postList.Posts[post.Id].UpdateAt, secondUpdateAt, "should've marked post as updated even if HasReactions doesn't change")
 
 	// different post
+	// create post1
+	post1, err := ss.Post().Save(&model.Post{
+		ChannelId: model.NewId(),
+		UserId:    model.NewId(),
+	})
+	require.NoError(t, err)
+
 	reaction3 := &model.Reaction{
 		UserId:    reaction1.UserId,
-		PostId:    model.NewId(),
+		PostId:    post1.Id,
 		EmojiName: reaction1.EmojiName,
 	}
 	_, nErr = ss.Reaction().Save(reaction3)
@@ -183,9 +191,21 @@ func testReactionDelete(t *testing.T, ss store.Store) {
 }
 
 func testReactionGetForPost(t *testing.T, ss store.Store) {
-	postId := model.NewId()
-
 	userId := model.NewId()
+	// create post
+	post, err := ss.Post().Save(&model.Post{
+		ChannelId: model.NewId(),
+		UserId:    userId,
+	})
+	require.NoError(t, err)
+	post1, err := ss.Post().Save(&model.Post{
+		ChannelId: model.NewId(),
+		UserId:    userId,
+	})
+	require.NoError(t, err)
+
+	postId := post.Id
+	post1Id := post1.Id
 
 	reactions := []*model.Reaction{
 		{
@@ -194,7 +214,7 @@ func testReactionGetForPost(t *testing.T, ss store.Store) {
 			EmojiName: "smile",
 		},
 		{
-			UserId:    model.NewId(),
+			UserId:    post1Id,
 			PostId:    postId,
 			EmojiName: "smile",
 		},
@@ -205,13 +225,13 @@ func testReactionGetForPost(t *testing.T, ss store.Store) {
 		},
 		{
 			UserId:    userId,
-			PostId:    model.NewId(),
+			PostId:    post1Id,
 			EmojiName: "angry",
 		},
 	}
 
 	for _, reaction := range reactions {
-		_, err := ss.Reaction().Save(reaction)
+		_, err = ss.Reaction().Save(reaction)
 		require.NoError(t, err)
 	}
 
@@ -276,9 +296,21 @@ func testReactionGetForPostSince(t *testing.T, ss store.Store, s SqlStore) {
 	now := model.GetMillis()
 	later := now + 1800000 // add 30 minutes
 	remoteId := model.NewId()
-
-	postId := model.NewId()
 	userId := model.NewId()
+
+	// create post
+	post, _ := ss.Post().Save(&model.Post{
+		ChannelId: model.NewId(),
+		UserId:    userId,
+	})
+	post1, _ := ss.Post().Save(&model.Post{
+		ChannelId: model.NewId(),
+		UserId:    userId,
+	})
+
+	postId := post.Id
+	post1Id := post1.Id
+
 	reactions := []*model.Reaction{
 		{
 			UserId:    userId,
@@ -300,7 +332,7 @@ func testReactionGetForPostSince(t *testing.T, ss store.Store, s SqlStore) {
 		},
 		{
 			UserId:    userId,
-			PostId:    model.NewId(),
+			PostId:    post1Id,
 			EmojiName: "angry",
 		},
 		{
@@ -591,12 +623,27 @@ func testReactionStorePermanentDeleteBatch(t *testing.T, ss store.Store) {
 }
 
 func testReactionBulkGetForPosts(t *testing.T, ss store.Store) {
-	postId := model.NewId()
-	post2Id := model.NewId()
-	post3Id := model.NewId()
-	post4Id := model.NewId()
-
 	userId := model.NewId()
+	post, _ := ss.Post().Save(&model.Post{
+		ChannelId: model.NewId(),
+		UserId:    userId,
+	})
+	postId := post.Id
+	post, _ = ss.Post().Save(&model.Post{
+		ChannelId: model.NewId(),
+		UserId:    userId,
+	})
+	post2Id := post.Id
+	post, _ = ss.Post().Save(&model.Post{
+		ChannelId: model.NewId(),
+		UserId:    userId,
+	})
+	post3Id := post.Id
+	post, _ = ss.Post().Save(&model.Post{
+		ChannelId: model.NewId(),
+		UserId:    userId,
+	})
+	post4Id := post.Id
 
 	reactions := []*model.Reaction{
 		{
@@ -663,7 +710,12 @@ func testReactionDeadlock(t *testing.T, ss store.Store) {
 		UserId:    model.NewId(),
 	})
 	require.NoError(t, err)
-
+	postId := post.Id
+	post, err = ss.Post().Save(&model.Post{
+		ChannelId: model.NewId(),
+		UserId:    model.NewId(),
+	})
+	require.NoError(t, err)
 	reaction1 := &model.Reaction{
 		UserId:    model.NewId(),
 		PostId:    post.Id,
@@ -684,7 +736,7 @@ func testReactionDeadlock(t *testing.T, ss store.Store) {
 	// different post
 	reaction3 := &model.Reaction{
 		UserId:    reaction1.UserId,
-		PostId:    model.NewId(),
+		PostId:    postId,
 		EmojiName: reaction1.EmojiName,
 	}
 	_, nErr = ss.Reaction().Save(reaction3)