Migrates the lastPostsCache from PostStore into cache layer (#13141)

* Some advances

* Partial advances

* Cache moved

* Tests finished

* Removed all test for PostStore (store/sqlstore) related with Cache. This is tested in the cache layer now

store/sqlstore/post_store.go

@@ -24,7 +24,6 @@ type SqlPostStore struct {
 	SqlStore
 	metrics           einterfaces.MetricsInterface
 	lastPostTimeCache *utils.Cache
-	lastPostsCache    *utils.Cache
 	maxPostSizeOnce   sync.Once
 	maxPostSizeCached int
 }
@@ -32,18 +31,13 @@ type SqlPostStore struct {
 const (
 	LAST_POST_TIME_CACHE_SIZE = 25000
 	LAST_POST_TIME_CACHE_SEC  = 900 // 15 minutes
-
-	LAST_POSTS_CACHE_SIZE = 1000
-	LAST_POSTS_CACHE_SEC  = 900 // 15 minutes
 )
 
 func (s *SqlPostStore) ClearCaches() {
 	s.lastPostTimeCache.Purge()
-	s.lastPostsCache.Purge()
 
 	if s.metrics != nil {
 		s.metrics.IncrementMemCacheInvalidationCounter("Last Post Time - Purge")
-		s.metrics.IncrementMemCacheInvalidationCounter("Last Posts Cache - Purge")
 	}
 }
 
@@ -52,7 +46,6 @@ func NewSqlPostStore(sqlStore SqlStore, metrics einterfaces.MetricsInterface) st
 		SqlStore:          sqlStore,
 		metrics:           metrics,
 		lastPostTimeCache: utils.NewLru(LAST_POST_TIME_CACHE_SIZE),
-		lastPostsCache:    utils.NewLru(LAST_POSTS_CACHE_SIZE),
 		maxPostSizeCached: model.POST_MESSAGE_MAX_RUNES_V1,
 	}
 
@@ -329,13 +322,8 @@ type etagPosts struct {
 func (s *SqlPostStore) InvalidateLastPostTimeCache(channelId string) {
 	s.lastPostTimeCache.Remove(channelId)
 
-	// Keys are "{channelid}{limit}" and caching only occurs on limits of 30 and 60
-	s.lastPostsCache.Remove(channelId + "30")
-	s.lastPostsCache.Remove(channelId + "60")
-
 	if s.metrics != nil {
 		s.metrics.IncrementMemCacheInvalidationCounter("Last Post Time - Remove by Channel Id")
-		s.metrics.IncrementMemCacheInvalidationCounter("Last Posts Cache - Remove by Channel Id")
 	}
 }
 
@@ -451,24 +439,11 @@ func (s *SqlPostStore) PermanentDeleteByChannel(channelId string) *model.AppErro
 	return nil
 }
 
-func (s *SqlPostStore) GetPosts(options model.GetPostsOptions, allowFromCache bool) (*model.PostList, *model.AppError) {
+func (s *SqlPostStore) GetPosts(options model.GetPostsOptions, _ bool) (*model.PostList, *model.AppError) {
 	if options.PerPage > 1000 {
 		return nil, model.NewAppError("SqlPostStore.GetLinearPosts", "store.sql_post.get_posts.app_error", nil, "channelId="+options.ChannelId, http.StatusBadRequest)
 	}
 	offset := options.PerPage * options.Page
-	// Caching only occurs on limits of 30 and 60, the common limits requested by MM clients
-	if allowFromCache && offset == 0 && (options.PerPage == 60 || options.PerPage == 30) {
-		if cacheItem, ok := s.lastPostsCache.Get(fmt.Sprintf("%s%v", options.ChannelId, options.PerPage)); ok {
-			if s.metrics != nil {
-				s.metrics.IncrementMemCacheHitCounter("Last Posts Cache")
-			}
-			return cacheItem.(*model.PostList), nil
-		}
-	}
-
-	if s.metrics != nil {
-		s.metrics.IncrementMemCacheMissCounter("Last Posts Cache")
-	}
 
 	rpc := make(chan store.StoreResult, 1)
 	go func() {
@@ -510,11 +485,6 @@ func (s *SqlPostStore) GetPosts(options model.GetPostsOptions, allowFromCache bo
 
 	list.MakeNonNil()
 
-	// Caching only occurs on limits of 30 and 60, the common limits requested by MM clients
-	if offset == 0 && (options.PerPage == 60 || options.PerPage == 30) {
-		s.lastPostsCache.AddWithExpiresInSecs(fmt.Sprintf("%s%v", options.ChannelId, options.PerPage), list, LAST_POSTS_CACHE_SEC)
-	}
-
 	return list, err
 }