enh: reuse tsdb cache reader

source/dnode/vnode/inc/vnode.h

@@ -193,6 +193,7 @@ void        *tsdbGetIdx(SMeta *pMeta);
 void        *tsdbGetIvtIdx(SMeta *pMeta);
 uint64_t     getReaderMaxVersion(STsdbReader *pReader);
 
+int32_t tsdbReuseCacherowsReader(void* pReader, void* pTableIdList, int32_t numOfTables);
 int32_t tsdbCacherowsReaderOpen(void *pVnode, int32_t type, void *pTableIdList, int32_t numOfTables, int32_t numOfCols,
                                 uint64_t suid, void **pReader, const char *idstr);
 int32_t tsdbRetrieveCacheRows(void *pReader, SSDataBlock *pResBlock, const int32_t *slotIds, SArray *pTableUids);

source/dnode/vnode/src/tsdb/tsdbCacheRead.c

@@ -142,6 +142,18 @@ static int32_t setTableSchema(SCacheRowsReader* p, uint64_t suid, const char* id
   return TSDB_CODE_SUCCESS;
 }
 
+int32_t tsdbReuseCacherowsReader(void* reader, void* pTableIdList, int32_t numOfTables) {
+  SCacheRowsReader* pReader = (SCacheRowsReader*)reader;
+
+  pReader->pTableList = pTableIdList;
+  pReader->numOfTables = numOfTables;
+  pReader->lastTs = INT64_MIN;
+
+  resetLastBlockLoadInfo(pReader->pLoadInfo);
+
+  return TSDB_CODE_SUCCESS;
+}
+
 int32_t tsdbCacherowsReaderOpen(void* pVnode, int32_t type, void* pTableIdList, int32_t numOfTables, int32_t numOfCols,
                                 uint64_t suid, void** pReader, const char* idstr) {
   *pReader = NULL;

source/libs/executor/src/cachescanoperator.c

@@ -224,13 +224,17 @@ SSDataBlock* doScanCache(SOperatorInfo* pOperator) {
         T_LONG_JMP(pTaskInfo->env, code);
       }
 
-      code = tsdbCacherowsReaderOpen(pInfo->readHandle.vnode, pInfo->retrieveType, pList, num,
-                                     taosArrayGetSize(pInfo->matchInfo.pList), suid, &pInfo->pLastrowReader,
-                                     pTaskInfo->id.str);
-      if (code != TSDB_CODE_SUCCESS) {
-        pInfo->currentGroupIndex += 1;
-        taosArrayClear(pInfo->pUidList);
-        continue;
+      if (NULL == pInfo->pLastrowReader) {
+        code = tsdbCacherowsReaderOpen(pInfo->readHandle.vnode, pInfo->retrieveType, pList, num,
+                                       taosArrayGetSize(pInfo->matchInfo.pList), suid, &pInfo->pLastrowReader,
+                                       pTaskInfo->id.str);
+        if (code != TSDB_CODE_SUCCESS) {
+          pInfo->currentGroupIndex += 1;
+          taosArrayClear(pInfo->pUidList);
+          continue;
+        }
+      } else {
+        tsdbReuseCacherowsReader(pInfo->pLastrowReader, pList, num);
       }
 
       taosArrayClear(pInfo->pUidList);
@@ -263,13 +267,14 @@ SSDataBlock* doScanCache(SOperatorInfo* pOperator) {
           }
         }
 
-        pInfo->pLastrowReader = tsdbCacherowsReaderClose(pInfo->pLastrowReader);
+        //pInfo->pLastrowReader = tsdbCacherowsReaderClose(pInfo->pLastrowReader);
         return pInfo->pRes;
       } else {
-        pInfo->pLastrowReader = tsdbCacherowsReaderClose(pInfo->pLastrowReader);
+        //pInfo->pLastrowReader = tsdbCacherowsReaderClose(pInfo->pLastrowReader);
       }
     }
 
+    pInfo->pLastrowReader = tsdbCacherowsReaderClose(pInfo->pLastrowReader);
     setOperatorCompleted(pOperator);
     return NULL;
   }