Merge pull request #16821 from taosdata/fix/3.0_bugfix_wxy

enh: count(tbname) optimize

source/libs/parser/src/parAstCreater.c

@@ -1303,7 +1303,7 @@ SNode* createShowStmtWithCond(SAstCreateContext* pCxt, ENodeType type, SNode* pD
                               EOperatorType tableCondType) {
   CHECK_PARSER_STATUS(pCxt);
   if (needDbShowStmt(type) && NULL == pDbName) {
-    snprintf(pCxt->pQueryCxt->pMsg, pCxt->pQueryCxt->msgLen, "db not specified");
+    snprintf(pCxt->pQueryCxt->pMsg, pCxt->pQueryCxt->msgLen, "database not specified");
     pCxt->errCode = TSDB_CODE_PAR_SYNTAX_ERROR;
     return NULL;
   }

source/libs/parser/src/parTranslater.c

@@ -1283,6 +1283,36 @@ static int32_t rewriteCountStar(STranslateContext* pCxt, SFunctionNode* pCount)
   return code;
 }
 
+static bool isCountTbname(SFunctionNode* pFunc) {
+  if (FUNCTION_TYPE_COUNT != pFunc->funcType || 1 != LIST_LENGTH(pFunc->pParameterList)) {
+    return false;
+  }
+  SNode* pPara = nodesListGetNode(pFunc->pParameterList, 0);
+  return (QUERY_NODE_FUNCTION == nodeType(pPara) && FUNCTION_TYPE_TBNAME == ((SFunctionNode*)pPara)->funcType);
+}
+
+// count(tbname) is rewritten as count(ts) for scannning optimization
+static int32_t rewriteCountTbname(STranslateContext* pCxt, SFunctionNode* pCount) {
+  SFunctionNode* pTbname = (SFunctionNode*)nodesListGetNode(pCount->pParameterList, 0);
+  const char*    pTableAlias = NULL;
+  if (LIST_LENGTH(pTbname->pParameterList) > 0) {
+    pTableAlias = ((SValueNode*)nodesListGetNode(pTbname->pParameterList, 0))->literal;
+  }
+  STableNode* pTable = NULL;
+  int32_t     code = findTable(pCxt, pTableAlias, &pTable);
+  if (TSDB_CODE_SUCCESS == code) {
+    SColumnNode* pCol = (SColumnNode*)nodesMakeNode(QUERY_NODE_COLUMN);
+    if (NULL == pCol) {
+      code = TSDB_CODE_OUT_OF_MEMORY;
+    } else {
+      setColumnInfoBySchema((SRealTableNode*)pTable, ((SRealTableNode*)pTable)->pMeta->schema, -1, pCol);
+      NODES_DESTORY_LIST(pCount->pParameterList);
+      code = nodesListMakeAppend(&pCount->pParameterList, (SNode*)pCol);
+    }
+  }
+  return code;
+}
+
 static bool hasInvalidFuncNesting(SNodeList* pParameterList) {
   bool hasInvalidFunc = false;
   nodesWalkExprs(pParameterList, haveVectorFunction, &hasInvalidFunc);
@@ -1318,6 +1348,9 @@ static int32_t translateAggFunc(STranslateContext* pCxt, SFunctionNode* pFunc) {
   if (isCountStar(pFunc)) {
     return rewriteCountStar(pCxt, pFunc);
   }
+  if (isCountTbname(pFunc)) {
+    return rewriteCountTbname(pCxt, pFunc);
+  }
   return TSDB_CODE_SUCCESS;
 }
 

source/libs/planner/test/planOptimizeTest.cpp

@@ -35,6 +35,8 @@ TEST_F(PlanOptimizeTest, scanPath) {
 
   run("SELECT LAST(c1) FROM t1 WHERE ts BETWEEN '2022-7-29 11:10:10' AND '2022-7-30 11:10:10' INTERVAL(10S) "
       "FILL(LINEAR)");
+
+  run("SELECT COUNT(TBNAME) FROM t1");
 }
 
 TEST_F(PlanOptimizeTest, pushDownCondition) {