fix: hit meta cache for collection aliases (#49513)

related: https://github.com/milvus-io/milvus/issues/49510

Signed-off-by: shaoting-huang <shaoting.huang@zilliz.com>

internal/proxy/meta_cache.go

@@ -432,6 +432,14 @@ func (m *MetaCache) getCollection(database, collectionName string, collectionID
 		if collection, ok := db[collectionName]; ok {
 			return collection, collection.isCollectionCached()
 		}
+		// update() stores alias requests under the real collection name.
+		if aliasDB, ok := m.aliasInfo[database]; ok {
+			if entry, ok := aliasDB[collectionName]; ok && entry.collectionName != "" {
+				if collection, ok := db[entry.collectionName]; ok {
+					return collection, collection.isCollectionCached()
+				}
+			}
+		}
 	}
 
 	return nil, false

internal/proxy/meta_cache_test.go

@@ -94,7 +94,7 @@ func (m *MockMixCoordClientInterface) ShowPartitions(ctx context.Context, in *mi
 	if m.Error {
 		return nil, errors.New("mocked error")
 	}
-	if in.CollectionName == "collection1" || in.CollectionID == 1 {
+	if in.CollectionName == "collection1" || in.CollectionName == "collection1_alias" || in.CollectionID == 1 {
 		return &milvuspb.ShowPartitionsResponse{
 			Status:               merr.Success(),
 			PartitionIDs:         []typeutil.UniqueID{1, 2},
@@ -137,7 +137,7 @@ func (m *MockMixCoordClientInterface) DescribeCollection(ctx context.Context, in
 		return nil, errors.New("mocked error")
 	}
 	m.IncAccessCount()
-	if in.CollectionName == "collection1" || in.CollectionID == 1 {
+	if in.CollectionName == "collection1" || in.CollectionName == "collection1_alias" || in.CollectionID == 1 {
 		return &milvuspb.DescribeCollectionResponse{
 			Status:       merr.Success(),
 			CollectionID: typeutil.UniqueID(1),
@@ -1016,6 +1016,36 @@ func TestMetaCache_GetCollection(t *testing.T) {
 	})
 }
 
+func TestMetaCache_GetCollectionByAliasHitsCache(t *testing.T) {
+	ctx := context.Background()
+	rootCoord := &MockMixCoordClientInterface{}
+
+	err := InitMetaCache(ctx, rootCoord)
+	assert.NoError(t, err)
+
+	id, err := globalMetaCache.GetCollectionID(ctx, dbName, "collection1_alias")
+	assert.NoError(t, err)
+	assert.Equal(t, typeutil.UniqueID(1), id)
+	assert.Equal(t, 1, rootCoord.GetAccessCount())
+
+	schema, err := globalMetaCache.GetCollectionSchema(ctx, dbName, "collection1_alias")
+	assert.NoError(t, err)
+	assert.Equal(t, "collection1", schema.GetName())
+	assert.Equal(t, 1, rootCoord.GetAccessCount())
+
+	info, err := globalMetaCache.GetCollectionInfo(ctx, dbName, "collection1_alias", 0)
+	assert.NoError(t, err)
+	assert.Equal(t, typeutil.UniqueID(1), info.collID)
+	assert.Equal(t, 1, rootCoord.GetAccessCount())
+
+	metaCache := globalMetaCache.(*MetaCache)
+	metaCache.mu.RLock()
+	defer metaCache.mu.RUnlock()
+	_, aliasCachedAsCollection := metaCache.collInfo[dbName]["collection1_alias"]
+	assert.False(t, aliasCachedAsCollection)
+	assert.Equal(t, "collection1", metaCache.aliasInfo[dbName]["collection1_alias"].collectionName)
+}
+
 func TestMetaCache_GetBasicCollectionInfo(t *testing.T) {
 	ctx := context.Background()
 	rootCoord := &MockMixCoordClientInterface{}