feat: sql command 'select constant'

source/libs/function/src/builtins.c

@@ -1799,7 +1799,7 @@ const SBuiltinFuncDefinition funcMgtBuiltins[] = {
   {
     .name = "last_row",
     .type = FUNCTION_TYPE_LAST_ROW,
-    .classification = FUNC_MGT_MULTI_RES_FUNC,
+    .classification = FUNC_MGT_AGG_FUNC | FUNC_MGT_MULTI_RES_FUNC,
     .translateFunc = translateLastRow,
     .getEnvFunc   = getMinmaxFuncEnv,
     .initFunc     = minmaxFunctionSetup,

source/libs/parser/inc/sql.y

@@ -757,8 +757,9 @@ boolean_primary(A) ::= NK_LP(C) boolean_value_expression(B) NK_RP(D).
 common_expression(A) ::= expression(B).                                           { A = B; }
 common_expression(A) ::= boolean_value_expression(B).                             { A = B; }
 
-/************************************************ from_clause *********************************************************/
-from_clause(A) ::= FROM table_reference_list(B).                                  { A = B; }
+/************************************************ from_clause_opt *********************************************************/
+from_clause_opt(A) ::= .                                                          { A = NULL; }
+from_clause_opt(A) ::= FROM table_reference_list(B).                              { A = B; }
 
 table_reference_list(A) ::= table_reference(B).                                   { A = B; }
 table_reference_list(A) ::= table_reference_list(B) NK_COMMA table_reference(C).  { A = createJoinTableNode(pCxt, JOIN_TYPE_INNER, B, C, NULL); }
@@ -792,9 +793,9 @@ join_type(A) ::= INNER.
 
 /************************************************ query_specification *************************************************/
 query_specification(A) ::=
-  SELECT set_quantifier_opt(B) select_list(C) from_clause(D) where_clause_opt(E) 
-    partition_by_clause_opt(F) range_opt(J) every_opt(K) fill_opt(L) twindow_clause_opt(G)
-    group_by_clause_opt(H) having_clause_opt(I).                                  { 
+  SELECT set_quantifier_opt(B) select_list(C) from_clause_opt(D) 
+  where_clause_opt(E) partition_by_clause_opt(F) range_opt(J) every_opt(K) 
+  fill_opt(L) twindow_clause_opt(G) group_by_clause_opt(H) having_clause_opt(I).  { 
                                                                                     A = createSelectStmt(pCxt, B, C, D);
                                                                                     A = addWhereClause(pCxt, A, E);
                                                                                     A = addPartitionByClause(pCxt, A, F);

source/libs/parser/src/parCalcConst.c

@@ -232,7 +232,11 @@ static int32_t calcConstGroupBy(SCalcConstContext* pCxt, SSelectStmt* pSelect) {
   return code;
 }
 
-static int32_t calcConstSelect(SCalcConstContext* pCxt, SSelectStmt* pSelect, bool subquery) {
+static int32_t calcConstSelectWithoutFrom(SCalcConstContext* pCxt, SSelectStmt* pSelect, bool subquery) {
+  return calcConstProjections(pCxt, pSelect, subquery);
+}
+
+static int32_t calcConstSelectFrom(SCalcConstContext* pCxt, SSelectStmt* pSelect, bool subquery) {
   int32_t code = calcConstFromTable(pCxt, pSelect->pFromTable);
   if (TSDB_CODE_SUCCESS == code) {
     code = calcConstProjections(pCxt, pSelect, subquery);
@@ -258,6 +262,14 @@ static int32_t calcConstSelect(SCalcConstContext* pCxt, SSelectStmt* pSelect, bo
   return code;
 }
 
+static int32_t calcConstSelect(SCalcConstContext* pCxt, SSelectStmt* pSelect, bool subquery) {
+  if (NULL == pSelect->pFromTable) {
+    return calcConstSelectWithoutFrom(pCxt, pSelect, subquery);
+  } else {
+    return calcConstSelectFrom(pCxt, pSelect, subquery);
+  }
+}
+
 static int32_t calcConstDelete(SCalcConstContext* pCxt, SDeleteStmt* pDelete) {
   int32_t code = calcConstFromTable(pCxt, pDelete->pFromTable);
   if (TSDB_CODE_SUCCESS == code) {

source/libs/parser/src/parTranslater.c

@@ -2466,7 +2466,13 @@ static int32_t replaceOrderByAlias(STranslateContext* pCxt, SNodeList* pProjecti
   return pCxt->errCode;
 }
 
-static int32_t translateSelect(STranslateContext* pCxt, SSelectStmt* pSelect) {
+static int32_t translateSelectWithoutFrom(STranslateContext* pCxt, SSelectStmt* pSelect) {
+  pCxt->pCurrSelectStmt = pSelect;
+  pCxt->currClause = SQL_CLAUSE_SELECT;
+  return translateExprList(pCxt, pSelect->pProjectionList);
+}
+
+static int32_t translateSelectFrom(STranslateContext* pCxt, SSelectStmt* pSelect) {
   pCxt->pCurrSelectStmt = pSelect;
   int32_t code = translateFrom(pCxt, pSelect->pFromTable);
   if (TSDB_CODE_SUCCESS == code) {
@@ -2515,6 +2521,14 @@ static int32_t translateSelect(STranslateContext* pCxt, SSelectStmt* pSelect) {
   return code;
 }
 
+static int32_t translateSelect(STranslateContext* pCxt, SSelectStmt* pSelect) {
+  if (NULL == pSelect->pFromTable) {
+    return translateSelectWithoutFrom(pCxt, pSelect);
+  } else {
+    return translateSelectFrom(pCxt, pSelect);
+  }
+}
+
 static SNode* createSetOperProject(const char* pTableAlias, SNode* pNode) {
   SColumnNode* pCol = (SColumnNode*)nodesMakeNode(QUERY_NODE_COLUMN);
   if (NULL == pCol) {

source/libs/parser/test/parSelectTest.cpp

@@ -388,4 +388,10 @@ TEST_F(ParserSelectTest, informationSchema) {
   run("SELECT * FROM information_schema.user_databases WHERE name = 'information_schema'");
 }
 
+TEST_F(ParserSelectTest, withoutFrom) {
+  useDb("root", "test");
+
+  run("SELECT 1");
+}
+
 }  // namespace ParserTest

source/libs/planner/src/planLogicCreater.c

@@ -901,7 +901,12 @@ static int32_t createDistinctLogicNode(SLogicPlanContext* pCxt, SSelectStmt* pSe
   return code;
 }
 
-static int32_t createSelectLogicNode(SLogicPlanContext* pCxt, SSelectStmt* pSelect, SLogicNode** pLogicNode) {
+static int32_t createSelectWithoutFromLogicNode(SLogicPlanContext* pCxt, SSelectStmt* pSelect,
+                                                SLogicNode** pLogicNode) {
+  return createProjectLogicNode(pCxt, pSelect, pLogicNode);
+}
+
+static int32_t createSelectFromLogicNode(SLogicPlanContext* pCxt, SSelectStmt* pSelect, SLogicNode** pLogicNode) {
   SLogicNode* pRoot = NULL;
   int32_t     code = createLogicNodeByTable(pCxt, pSelect, pSelect->pFromTable, &pRoot);
   if (TSDB_CODE_SUCCESS == code) {
@@ -941,6 +946,14 @@ static int32_t createSelectLogicNode(SLogicPlanContext* pCxt, SSelectStmt* pSele
   return code;
 }
 
+static int32_t createSelectLogicNode(SLogicPlanContext* pCxt, SSelectStmt* pSelect, SLogicNode** pLogicNode) {
+  if (NULL == pSelect->pFromTable) {
+    return createSelectWithoutFromLogicNode(pCxt, pSelect, pLogicNode);
+  } else {
+    return createSelectFromLogicNode(pCxt, pSelect, pLogicNode);
+  }
+}
+
 static int32_t createSetOpRootLogicNode(SLogicPlanContext* pCxt, SSetOperator* pSetOperator, FCreateSetOpLogicNode func,
                                         SLogicNode** pRoot) {
   return createRootLogicNode(pCxt, pSetOperator, pSetOperator->precision, (FCreateLogicNode)func, pRoot);

source/libs/planner/src/planOptimizer.c

@@ -293,16 +293,22 @@ static int32_t cpdCondAppend(SNode** pCond, SNode** pAdditionalCond) {
   return code;
 }
 
-static int32_t cpdCalcTimeRange(SScanLogicNode* pScan, SNode** pPrimaryKeyCond, SNode** pOtherCond) {
-  bool    isStrict = false;
-  int32_t code = filterGetTimeRange(*pPrimaryKeyCond, &pScan->scanRange, &isStrict);
-  if (TSDB_CODE_SUCCESS == code) {
-    if (isStrict) {
-      nodesDestroyNode(*pPrimaryKeyCond);
-    } else {
-      code = cpdCondAppend(pOtherCond, pPrimaryKeyCond);
+static int32_t cpdCalcTimeRange(SOptimizeContext* pCxt, SScanLogicNode* pScan, SNode** pPrimaryKeyCond,
+                                SNode** pOtherCond) {
+  int32_t code = TSDB_CODE_SUCCESS;
+  if (pCxt->pPlanCxt->topicQuery || pCxt->pPlanCxt->streamQuery) {
+    code = cpdCondAppend(pOtherCond, pPrimaryKeyCond);
+  } else {
+    bool isStrict = false;
+    code = filterGetTimeRange(*pPrimaryKeyCond, &pScan->scanRange, &isStrict);
+    if (TSDB_CODE_SUCCESS == code) {
+      if (isStrict) {
+        nodesDestroyNode(*pPrimaryKeyCond);
+      } else {
+        code = cpdCondAppend(pOtherCond, pPrimaryKeyCond);
+      }
+      *pPrimaryKeyCond = NULL;
     }
-    *pPrimaryKeyCond = NULL;
   }
   return code;
 }
@@ -344,7 +350,7 @@ static int32_t cpdOptimizeScanCondition(SOptimizeContext* pCxt, SScanLogicNode*
   SNode*  pOtherCond = NULL;
   int32_t code = nodesPartitionCond(&pScan->node.pConditions, &pPrimaryKeyCond, &pTagCond, &pOtherCond);
   if (TSDB_CODE_SUCCESS == code && NULL != pPrimaryKeyCond) {
-    code = cpdCalcTimeRange(pScan, &pPrimaryKeyCond, &pOtherCond);
+    code = cpdCalcTimeRange(pCxt, pScan, &pPrimaryKeyCond, &pOtherCond);
   }
   if (TSDB_CODE_SUCCESS == code && NULL != pTagCond) {
     code = cpdApplyTagIndex(pScan, &pTagCond, &pOtherCond);

source/libs/planner/src/planPhysiCreater.c

@@ -917,8 +917,16 @@ static int32_t createProjectPhysiNode(SPhysiPlanContext* pCxt, SNodeList* pChild
   pProject->slimit = pProjectLogicNode->slimit;
   pProject->soffset = pProjectLogicNode->soffset;
 
-  int32_t code = setListSlotId(pCxt, ((SPhysiNode*)nodesListGetNode(pChildren, 0))->pOutputDataBlockDesc->dataBlockId,
-                               -1, pProjectLogicNode->pProjections, &pProject->pProjections);
+  int32_t code = TSDB_CODE_SUCCESS;
+  if (0 == LIST_LENGTH(pChildren)) {
+    pProject->pProjections = nodesCloneList(pProjectLogicNode->pProjections);
+    if (NULL == pProject->pProjections) {
+      code = TSDB_CODE_OUT_OF_MEMORY;
+    }
+  } else {
+    code = setListSlotId(pCxt, ((SPhysiNode*)nodesListGetNode(pChildren, 0))->pOutputDataBlockDesc->dataBlockId, -1,
+                         pProjectLogicNode->pProjections, &pProject->pProjections);
+  }
   if (TSDB_CODE_SUCCESS == code) {
     code = addDataBlockSlotsForProject(pCxt, pProjectLogicNode->stmtName, pProject->pProjections,
                                        pProject->node.pOutputDataBlockDesc);

source/libs/planner/test/planBasicTest.cpp

@@ -95,3 +95,9 @@ TEST_F(PlanBasicTest, lastRowFunc) {
 
   run("SELECT LAST_ROW(c1) FROM st1");
 }
+
+TEST_F(PlanBasicTest, withoutFrom) {
+  useDb("root", "test");
+
+  run("SELECT 1");
+}