fix: add del mark for last cache

source/dnode/vnode/src/inc/tsdb.h

@@ -343,7 +343,6 @@ typedef struct {
   rocksdb_readoptions_t               *readoptions;
   rocksdb_writebatch_t                *writebatch;
   rocksdb_writebatch_t                *rwritebatch;
-  TdThreadMutex                        rMutex;
   STSchema                            *pTSchema;
 } SRocksCache;
 
@@ -915,12 +914,21 @@ typedef enum {
   READER_EXEC_ROWS = 0x2,
 } EExecMode;
 
-#define LAST_COL_VERSION (0x1)
+#define LAST_COL_VERSION_1 (0x1) // add primary key, version
+#define LAST_COL_VERSION_2 (0x2) // add cache status
+#define LAST_COL_VERSION   LAST_COL_VERSION_2
+
+typedef enum {
+  TSDB_LAST_CACHE_VALID = 0, // last_cache has valid data
+  TSDB_LAST_CACHE_EMPTY,     // neither last_cache nor tsdb has data
+  TSDB_LAST_CACHE_NO_CACHE,  // last_cache has no data, but tsdb may have data
+} ELastCacheStatus;
 
 typedef struct {
   SRowKey          rowKey;
   int8_t           dirty;
   SColVal          colVal;
+  ELastCacheStatus cacheStatus;
 } SLastCol;
 
 typedef struct {