diff --git a/source/libs/function/inc/builtinsimpl.h b/source/libs/function/inc/builtinsimpl.h
index 06944edadd..e8e37e5c6b 100644
--- a/source/libs/function/inc/builtinsimpl.h
+++ b/source/libs/function/inc/builtinsimpl.h
@@ -157,6 +157,7 @@ int32_t elapsedCombine(SqlFunctionCtx* pDestCtx, SqlFunctionCtx* pSourceCtx);
 bool getHistogramFuncEnv(struct SFunctionNode* pFunc, SFuncExecEnv* pEnv);
 bool histogramFunctionSetup(SqlFunctionCtx *pCtx, SResultRowEntryInfo* pResultInfo);
 int32_t histogramFunction(SqlFunctionCtx* pCtx);
+int32_t histogramFunctionPartial(SqlFunctionCtx* pCtx);
 int32_t histogramFunctionMerge(SqlFunctionCtx* pCtx);
 int32_t histogramFinalize(SqlFunctionCtx* pCtx, SSDataBlock* pBlock);
 int32_t histogramPartialFinalize(SqlFunctionCtx* pCtx, SSDataBlock* pBlock);
diff --git a/source/libs/function/src/builtins.c b/source/libs/function/src/builtins.c
index fc87ba964a..a735edafab 100644
--- a/source/libs/function/src/builtins.c
+++ b/source/libs/function/src/builtins.c
@@ -1427,9 +1427,12 @@ static int32_t translateIrate(SFunctionNode* pFunc, char* pErrBuf, int32_t len)
 }
 
 static int32_t translateFirstLast(SFunctionNode* pFunc, char* pErrBuf, int32_t len) {
-  // first(col_list) will be rewritten as first(col)
-  if (1 != LIST_LENGTH(pFunc->pParameterList)) {
-    return TSDB_CODE_SUCCESS;
+  int32_t numOfParams = LIST_LENGTH(pFunc->pParameterList);
+  for (int32_t i = 0; i < numOfParams; ++i) {
+    SNode* pParamNode = nodesListGetNode(pFunc->pParameterList, i);
+    if (QUERY_NODE_VALUE == nodeType(pParamNode)) {
+      return invaildFuncParaValueErrMsg(pErrBuf, len, pFunc->functionName);
+    }
   }
 
   pFunc->node.resType = ((SExprNode*)nodesListGetNode(pFunc->pParameterList, 0))->resType;
@@ -2323,7 +2326,7 @@ const SBuiltinFuncDefinition funcMgtBuiltins[] = {
     .translateFunc = translateHistogramPartial,
     .getEnvFunc   = getHistogramFuncEnv,
     .initFunc     = histogramFunctionSetup,
-    .processFunc  = histogramFunction,
+    .processFunc  = histogramFunctionPartial,
     .finalizeFunc = histogramPartialFinalize,
     .invertFunc   = NULL,
     .combineFunc  = histogramCombine,
diff --git a/source/libs/function/src/builtinsimpl.c b/source/libs/function/src/builtinsimpl.c
index 4bf49a05f9..78778df173 100644
--- a/source/libs/function/src/builtinsimpl.c
+++ b/source/libs/function/src/builtinsimpl.c
@@ -4096,7 +4096,7 @@ bool histogramFunctionSetup(SqlFunctionCtx* pCtx, SResultRowEntryInfo* pResultIn
   return true;
 }
 
-int32_t histogramFunction(SqlFunctionCtx* pCtx) {
+static int32_t histogramFunctionImpl(SqlFunctionCtx* pCtx, bool isPartial) {
   SHistoFuncInfo* pInfo = GET_ROWCELL_INTERBUF(GET_RES_INFO(pCtx));
 
   SInputColumnInfoData* pInput = &pCtx->input;
@@ -4128,10 +4128,22 @@ int32_t histogramFunction(SqlFunctionCtx* pCtx) {
     }
   }
 
-  SET_VAL(GET_RES_INFO(pCtx), numOfElems, pInfo->numOfBins);
+  if (!isPartial) {
+    SET_VAL(GET_RES_INFO(pCtx), numOfElems, pInfo->numOfBins);
+  } else {
+    SET_VAL(GET_RES_INFO(pCtx), numOfElems, 1);
+  }
   return TSDB_CODE_SUCCESS;
 }
 
+int32_t histogramFunction(SqlFunctionCtx* pCtx) {
+  return histogramFunctionImpl(pCtx, false);
+}
+
+int32_t histogramFunctionPartial(SqlFunctionCtx* pCtx) {
+  return histogramFunctionImpl(pCtx, true);
+}
+
 static void histogramTransferInfo(SHistoFuncInfo* pInput, SHistoFuncInfo* pOutput) {
   pOutput->normalized = pInput->normalized;
   pOutput->numOfBins = pInput->numOfBins;
@@ -4151,10 +4163,12 @@ int32_t histogramFunctionMerge(SqlFunctionCtx* pCtx) {
   SHistoFuncInfo* pInfo = GET_ROWCELL_INTERBUF(GET_RES_INFO(pCtx));
 
   int32_t         start = pInput->startRowIndex;
-  char*           data = colDataGetData(pCol, start);
-  SHistoFuncInfo* pInputInfo = (SHistoFuncInfo*)varDataVal(data);
 
-  histogramTransferInfo(pInputInfo, pInfo);
+  for(int32_t i = start; i < start + pInput->numOfRows; ++i) {
+    char*       data = colDataGetData(pCol, i);
+    SHistoFuncInfo* pInputInfo = (SHistoFuncInfo*)varDataVal(data);
+    histogramTransferInfo(pInputInfo, pInfo);
+  }
 
   SET_VAL(GET_RES_INFO(pCtx), pInfo->numOfBins, pInfo->numOfBins);
   return TSDB_CODE_SUCCESS;
@@ -4197,6 +4211,7 @@ int32_t histogramFinalize(SqlFunctionCtx* pCtx, SSDataBlock* pBlock) {
 }
 
 int32_t histogramPartialFinalize(SqlFunctionCtx* pCtx, SSDataBlock* pBlock) {
+  SResultRowEntryInfo* pResInfo = GET_RES_INFO(pCtx);
   SHistoFuncInfo* pInfo = GET_ROWCELL_INTERBUF(GET_RES_INFO(pCtx));
   int32_t         resultBytes = getHistogramInfoSize();
   char*           res = taosMemoryCalloc(resultBytes + VARSTR_HEADER_SIZE, sizeof(char));
@@ -4210,7 +4225,7 @@ int32_t histogramPartialFinalize(SqlFunctionCtx* pCtx, SSDataBlock* pBlock) {
   colDataAppend(pCol, pBlock->info.rows, res, false);
 
   taosMemoryFree(res);
-  return 1;
+  return pResInfo->numOfRes;
 }
 
 int32_t histogramCombine(SqlFunctionCtx* pDestCtx, SqlFunctionCtx* pSourceCtx) {
diff --git a/source/libs/planner/src/planOptimizer.c b/source/libs/planner/src/planOptimizer.c
index 12d1d280c9..855427f26e 100644
--- a/source/libs/planner/src/planOptimizer.c
+++ b/source/libs/planner/src/planOptimizer.c
@@ -1364,9 +1364,9 @@ static EDealRes partTagsOptHasColImpl(SNode* pNode, void* pContext) {
   return DEAL_RES_CONTINUE;
 }
 
-static bool partTagsOptHasCol(SNodeList* pPartKeys) {
+static bool planOptNodeListHasCol(SNodeList* pKeys) {
   bool hasCol = false;
-  nodesWalkExprs(pPartKeys, partTagsOptHasColImpl, &hasCol);
+  nodesWalkExprs(pKeys, partTagsOptHasColImpl, &hasCol);
   return hasCol;
 }
 
@@ -1409,7 +1409,7 @@ static bool partTagsOptMayBeOptimized(SLogicNode* pNode) {
     return false;
   }
 
-  return !partTagsOptHasCol(partTagsGetPartKeys(pNode)) && partTagsOptAreSupportedFuncs(partTagsGetFuncs(pNode));
+  return !planOptNodeListHasCol(partTagsGetPartKeys(pNode)) && partTagsOptAreSupportedFuncs(partTagsGetFuncs(pNode));
 }
 
 static int32_t partTagsOptRebuildTbanme(SNodeList* pPartKeys) {
@@ -2096,6 +2096,37 @@ static int32_t mergeProjectsOptimize(SOptimizeContext* pCxt, SLogicSubplan* pLog
   return mergeProjectsOptimizeImpl(pCxt, pLogicSubplan, pProjectNode);
 }
 
+static bool tagScanMayBeOptimized(SLogicNode* pNode) {
+  if (QUERY_NODE_LOGIC_PLAN_SCAN != nodeType(pNode) || (SCAN_TYPE_TAG == ((SScanLogicNode*)pNode)->scanType)) {
+    return false;
+  }
+  SScanLogicNode *pScan = (SScanLogicNode*)pNode;
+  if (NULL != pScan->pScanCols) {
+    return false;
+  }
+  if (NULL == pNode->pParent || QUERY_NODE_LOGIC_PLAN_AGG != nodeType(pNode->pParent) || 1 != LIST_LENGTH(pNode->pParent->pChildren)) {
+    return false;
+  }
+
+  SAggLogicNode* pAgg = (SAggLogicNode*)(pNode->pParent);
+  if (NULL == pAgg->pGroupKeys || NULL != pAgg->pAggFuncs || planOptNodeListHasCol(pAgg->pGroupKeys)) {
+    return false;
+  }
+
+  return true;
+}
+
+static int32_t tagScanOptimize(SOptimizeContext* pCxt, SLogicSubplan* pLogicSubplan) {
+  SScanLogicNode* pScanNode = (SScanLogicNode*)optFindPossibleNode(pLogicSubplan->pNode, tagScanMayBeOptimized);
+  if (NULL == pScanNode) {
+    return TSDB_CODE_SUCCESS;
+  }
+
+  pScanNode->scanType = SCAN_TYPE_TAG;
+  pCxt->optimized = true;
+  return TSDB_CODE_SUCCESS;
+}
+
 // clang-format off
 static const SOptimizeRule optimizeRuleSet[] = {
   {.pName = "ScanPath",                   .optimizeFunc = scanPathOptimize},
@@ -2108,7 +2139,8 @@ static const SOptimizeRule optimizeRuleSet[] = {
   {.pName = "EliminateSetOperator",       .optimizeFunc = eliminateSetOpOptimize},
   {.pName = "RewriteTail",                .optimizeFunc = rewriteTailOptimize},
   {.pName = "RewriteUnique",              .optimizeFunc = rewriteUniqueOptimize},
-  {.pName = "LastRowScan",                .optimizeFunc = lastRowScanOptimize}
+  {.pName = "LastRowScan",               .optimizeFunc = lastRowScanOptimize},
+  {.pName = "TagScan",                   .optimizeFunc = tagScanOptimize}
 };
 // clang-format on
 
diff --git a/source/libs/planner/test/planOptimizeTest.cpp b/source/libs/planner/test/planOptimizeTest.cpp
index ef056c5ec8..316148df27 100644
--- a/source/libs/planner/test/planOptimizeTest.cpp
+++ b/source/libs/planner/test/planOptimizeTest.cpp
@@ -87,4 +87,11 @@ TEST_F(PlanOptimizeTest, eliminateProjection) {
 TEST_F(PlanOptimizeTest, pushDownProjectCond) {
   useDb("root", "test");
   run("select 1-abs(c1) from (select unique(c1) c1 from st1s3) where 1-c1>5 order by 1 nulls first");
+}
+
+TEST_F(PlanOptimizeTest, tagScan) {
+  useDb("root", "test");
+  run("select tag1 from st1 group by tag1");
+  run("select distinct tag1 from st1");
+  run("select tag1*tag1 from st1 group by tag1*tag1");
 }
\ No newline at end of file
diff --git a/source/libs/transport/inc/transComm.h b/source/libs/transport/inc/transComm.h
index f29ff3769b..5bb6349d9b 100644
--- a/source/libs/transport/inc/transComm.h
+++ b/source/libs/transport/inc/transComm.h
@@ -317,6 +317,11 @@ typedef struct STransReq {
   void* data;
 } STransReq;
 
+void  transReqQueueInit(queue* q);
+void* transReqQueuePushReq(queue* q);
+void* transReqQueueRemove(void* arg);
+void  transReqQueueClear(queue* q);
+
 // queue sending msgs
 typedef struct {
   SArray* q;
diff --git a/source/libs/transport/src/transCli.c b/source/libs/transport/src/transCli.c
index f5110f2471..5d087d5769 100644
--- a/source/libs/transport/src/transCli.c
+++ b/source/libs/transport/src/transCli.c
@@ -19,7 +19,7 @@ typedef struct SCliConn {
   T_REF_DECLARE()
   uv_connect_t connReq;
   uv_stream_t* stream;
-  uv_write_t   writeReq;
+  queue        wreqQueue;
 
   void* hostThrd;
 
@@ -586,9 +586,10 @@ static SCliConn* cliCreateConn(SCliThrd* pThrd) {
   uv_tcp_init(pThrd->loop, (uv_tcp_t*)(conn->stream));
   conn->stream->data = conn;
 
-  conn->writeReq.data = conn;
   conn->connReq.data = conn;
 
+  transReqQueueInit(&conn->wreqQueue);
+
   transQueueInit(&conn->cliMsgs, NULL);
   QUEUE_INIT(&conn->conn);
   conn->hostThrd = pThrd;
@@ -627,6 +628,8 @@ static void cliDestroy(uv_handle_t* handle) {
   transCtxCleanup(&conn->ctx);
   transQueueDestroy(&conn->cliMsgs);
   tTrace("%s conn %p destroy successfully", CONN_GET_INST_LABEL(conn), conn);
+  transReqQueueClear(&conn->wreqQueue);
+
   transDestroyBuffer(&conn->readBuf);
   taosMemoryFree(conn);
 }
@@ -649,11 +652,8 @@ static bool cliHandleNoResp(SCliConn* conn) {
   return res;
 }
 static void cliSendCb(uv_write_t* req, int status) {
-  SCliConn* pConn = req && req->handle ? req->handle->data : NULL;
-  taosMemoryFree(req);
-  if (pConn == NULL) {
-    return;
-  }
+  SCliConn* pConn = transReqQueueRemove(req);
+  if (pConn == NULL) return;
 
   if (status == 0) {
     tTrace("%s conn %p data already was written out", CONN_GET_INST_LABEL(pConn), pConn);
@@ -711,7 +711,7 @@ void cliSend(SCliConn* pConn) {
     CONN_SET_PERSIST_BY_APP(pConn);
   }
 
-  uv_write_t* req = taosMemoryCalloc(1, sizeof(uv_write_t));
+  uv_write_t* req = transReqQueuePushReq(&pConn->wreqQueue);
   uv_write(req, (uv_stream_t*)pConn->stream, &wb, 1, cliSendCb);
   return;
 _RETURN:
diff --git a/source/libs/transport/src/transComm.c b/source/libs/transport/src/transComm.c
index 812123441c..3ab15ad804 100644
--- a/source/libs/transport/src/transComm.c
+++ b/source/libs/transport/src/transComm.c
@@ -293,6 +293,48 @@ void* transCtxDumpBrokenlinkVal(STransCtx* ctx, int32_t* msgType) {
   return ret;
 }
 
+void transReqQueueInit(queue* q) {
+  // init  req queue
+  QUEUE_INIT(q);
+}
+void* transReqQueuePushReq(queue* q) {
+  uv_write_t* req = taosMemoryCalloc(1, sizeof(uv_write_t));
+  STransReq*  wreq = taosMemoryCalloc(1, sizeof(STransReq));
+  wreq->data = req;
+  req->data = wreq;
+  QUEUE_PUSH(q, &wreq->q);
+  return req;
+}
+void* transReqQueueRemove(void* arg) {
+  void*       ret = NULL;
+  uv_write_t* req = arg;
+  STransReq*  wreq = req && req->data ? req->data : NULL;
+
+  assert(wreq->data == req);
+  if (wreq == NULL || wreq->data == NULL) {
+    taosMemoryFree(wreq->data);
+    taosMemoryFree(wreq);
+    return req;
+  }
+
+  QUEUE_REMOVE(&wreq->q);
+
+  ret = req && req->handle ? req->handle->data : NULL;
+  taosMemoryFree(wreq->data);
+  taosMemoryFree(wreq);
+
+  return ret;
+}
+void transReqQueueClear(queue* q) {
+  while (!QUEUE_IS_EMPTY(q)) {
+    queue* h = QUEUE_HEAD(q);
+    QUEUE_REMOVE(h);
+    STransReq* req = QUEUE_DATA(h, STransReq, q);
+    taosMemoryFree(req->data);
+    taosMemoryFree(req);
+  }
+}
+
 void transQueueInit(STransQueue* queue, void (*freeFunc)(const void* arg)) {
   queue->q = taosArrayInit(2, sizeof(void*));
   queue->freeFunc = (void (*)(const void*))freeFunc;
diff --git a/source/libs/transport/src/transSvr.c b/source/libs/transport/src/transSvr.c
index fb11465d4a..fbf6c0df76 100644
--- a/source/libs/transport/src/transSvr.c
+++ b/source/libs/transport/src/transSvr.c
@@ -331,14 +331,7 @@ void uvOnTimeoutCb(uv_timer_t* handle) {
 }
 
 void uvOnSendCb(uv_write_t* req, int status) {
-  STransReq* wreq = req && req->data ? req->data : NULL;
-  SSvrConn*  conn = req && req->handle ? req->handle->data : NULL;
-  if (wreq != NULL && conn != NULL) {
-    QUEUE_REMOVE(&wreq->q);
-    taosMemoryFree(wreq->data);
-    taosMemoryFree(wreq);
-  }
-
+  SSvrConn* conn = transReqQueueRemove(req);
   if (conn == NULL) return;
 
   if (status == 0) {
@@ -442,12 +435,7 @@ static void uvStartSendRespInternal(SSvrMsg* smsg) {
 
   transRefSrvHandle(pConn);
 
-  uv_write_t* req = taosMemoryCalloc(1, sizeof(uv_write_t));
-  STransReq*  wreq = taosMemoryCalloc(1, sizeof(STransReq));
-  wreq->data = req;
-  req->data = wreq;
-  QUEUE_PUSH(&pConn->wreqQueue, &wreq->q);
-
+  uv_write_t* req = transReqQueuePushReq(&pConn->wreqQueue);
   uv_write(req, (uv_stream_t*)pConn->pTcp, &wb, 1, uvOnSendCb);
 }
 static void uvStartSendResp(SSvrMsg* smsg) {
@@ -757,7 +745,7 @@ static SSvrConn* createConn(void* hThrd) {
 
   SSvrConn* pConn = (SSvrConn*)taosMemoryCalloc(1, sizeof(SSvrConn));
 
-  QUEUE_INIT(&pConn->wreqQueue);
+  transReqQueueInit(&pConn->wreqQueue);
   QUEUE_INIT(&pConn->queue);
 
   QUEUE_PUSH(&pThrd->conn, &pConn->queue);
@@ -834,13 +822,7 @@ static void uvDestroyConn(uv_handle_t* handle) {
     destroySmsg(msg);
   }
 
-  while (!QUEUE_IS_EMPTY(&conn->wreqQueue)) {
-    queue* h = QUEUE_HEAD(&conn->wreqQueue);
-    QUEUE_REMOVE(h);
-    STransReq* req = QUEUE_DATA(h, STransReq, q);
-    taosMemoryFree(req->data);
-    taosMemoryFree(req);
-  }
+  transReqQueueClear(&conn->wreqQueue);
   transQueueDestroy(&conn->srvMsgs);
 
   QUEUE_REMOVE(&conn->queue);
diff --git a/tests/script/tsim/valgrind/checkError1.sim b/tests/script/tsim/valgrind/checkError1.sim
index 9e73e006c2..1a76d8ce5c 100644
--- a/tests/script/tsim/valgrind/checkError1.sim
+++ b/tests/script/tsim/valgrind/checkError1.sim
@@ -98,7 +98,7 @@ print ----> start to check if there are ERRORS in vagrind log file for each dnod
 system_content sh/checkValgrind.sh -n dnode1 
 
 print cmd return result ----> [ $system_content ]
-if $system_content <= 2 then
+if $system_content <= 0 then
   return 0
 endi 
 
diff --git a/tests/script/tsim/valgrind/checkError2.sim b/tests/script/tsim/valgrind/checkError2.sim
index e2ac9577e0..e9dfc0eb4e 100644
--- a/tests/script/tsim/valgrind/checkError2.sim
+++ b/tests/script/tsim/valgrind/checkError2.sim
@@ -58,7 +58,7 @@ print ----> start to check if there are ERRORS in vagrind log file for each dnod
 system_content sh/checkValgrind.sh -n dnode1 
 
 print cmd return result ----> [ $system_content ]
-if $system_content <= 2 then
+if $system_content <= 0 then
   return 0
 endi