refactor: do some internal refactor.

source/libs/executor/src/cachescanoperator.c

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <jhtao@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "os.h"
+#include "function.h"
+#include "tname.h"
+
+#include "tdatablock.h"
+#include "tmsg.h"
+
+#include "executorimpl.h"
+#include "tcompare.h"
+#include "thash.h"
+#include "ttypes.h"
+#include "executorInt.h"
+
+static SSDataBlock* doScanLastrow(SOperatorInfo* pOperator);
+static void destroyLastrowScanOperator(void* param, int32_t numOfOutput);
+static int32_t extractTargetSlotId(const SArray* pColMatchInfo, SExecTaskInfo* pTaskInfo, int32_t** pSlotIds);
+
+SOperatorInfo* createLastrowScanOperator(SLastRowScanPhysiNode* pScanNode, SReadHandle* readHandle, SArray* pTableList,
+                                         SExecTaskInfo* pTaskInfo) {
+  SLastrowScanInfo* pInfo = taosMemoryCalloc(1, sizeof(SLastrowScanInfo));
+  SOperatorInfo*    pOperator = taosMemoryCalloc(1, sizeof(SOperatorInfo));
+  if (pInfo == NULL || pOperator == NULL) {
+    goto _error;
+  }
+
+  pInfo->pTableList = pTableList;
+  pInfo->readHandle = *readHandle;
+  pInfo->pRes = createResDataBlock(pScanNode->node.pOutputDataBlockDesc);
+
+  int32_t numOfCols = 0;
+  pInfo->pColMatchInfo = extractColMatchInfo(pScanNode->pScanCols, pScanNode->node.pOutputDataBlockDesc, &numOfCols,
+                                             COL_MATCH_FROM_COL_ID);
+  int32_t* pCols = taosMemoryMalloc(numOfCols * sizeof(int32_t));
+  for (int32_t i = 0; i < numOfCols; ++i) {
+    SColMatchInfo* pColMatch = taosArrayGet(pInfo->pColMatchInfo, i);
+    pCols[i] = pColMatch->colId;
+  }
+
+  int32_t code = extractTargetSlotId(pInfo->pColMatchInfo, pTaskInfo, &pInfo->pSlotIds);
+  if (code != TSDB_CODE_SUCCESS) {
+    goto _error;
+  }
+
+  tsdbLastRowReaderOpen(readHandle->vnode, LASTROW_RETRIEVE_TYPE_ALL, pTableList, pCols, numOfCols,
+                        &pInfo->pLastrowReader);
+  taosMemoryFree(pCols);
+
+  pOperator->name = "LastrowScanOperator";
+  pOperator->operatorType = QUERY_NODE_PHYSICAL_PLAN_LAST_ROW_SCAN;
+  pOperator->blocking = false;
+  pOperator->status = OP_NOT_OPENED;
+  pOperator->info = pInfo;
+  pOperator->pTaskInfo = pTaskInfo;
+  pOperator->exprSupp.numOfExprs = taosArrayGetSize(pInfo->pRes->pDataBlock);
+
+  initResultSizeInfo(pOperator, 1024);
+  blockDataEnsureCapacity(pInfo->pRes, pOperator->resultInfo.capacity);
+
+  pOperator->fpSet =
+      createOperatorFpSet(operatorDummyOpenFn, doScanLastrow, NULL, NULL, destroyLastrowScanOperator, NULL, NULL, NULL);
+  pOperator->cost.openCost = 0;
+  return pOperator;
+
+  _error:
+  pTaskInfo->code = TSDB_CODE_OUT_OF_MEMORY;
+  taosMemoryFree(pInfo);
+  taosMemoryFree(pOperator);
+  return NULL;
+}
+
+SSDataBlock* doScanLastrow(SOperatorInfo* pOperator) {
+  if (pOperator->status == OP_EXEC_DONE) {
+    return NULL;
+  }
+
+  SLastrowScanInfo* pInfo = pOperator->info;
+  SExecTaskInfo*    pTaskInfo = pOperator->pTaskInfo;
+
+  int32_t size = taosArrayGetSize(pInfo->pTableList);
+  if (size == 0) {
+    setTaskStatus(pTaskInfo, TASK_COMPLETED);
+    return NULL;
+  }
+
+  // check if it is a group by tbname
+  if (size == taosArrayGetSize(pInfo->pTableList)) {
+    blockDataCleanup(pInfo->pRes);
+    tsdbRetrieveLastRow(pInfo->pLastrowReader, pInfo->pRes, pInfo->pSlotIds);
+    return (pInfo->pRes->info.rows == 0) ? NULL : pInfo->pRes;
+  } else {
+    // todo fetch the result for each group
+  }
+
+  return pInfo->pRes->info.rows == 0 ? NULL : pInfo->pRes;
+}
+
+void destroyLastrowScanOperator(void* param, int32_t numOfOutput) {
+  SLastrowScanInfo* pInfo = (SLastrowScanInfo*)param;
+  blockDataDestroy(pInfo->pRes);
+  tsdbLastrowReaderClose(pInfo->pLastrowReader);
+
+  taosMemoryFreeClear(param);
+}
+
+int32_t extractTargetSlotId(const SArray* pColMatchInfo, SExecTaskInfo* pTaskInfo, int32_t** pSlotIds) {
+  size_t   numOfCols = taosArrayGetSize(pColMatchInfo);
+
+  *pSlotIds = taosMemoryMalloc(numOfCols * sizeof(int32_t));
+  if (*pSlotIds == NULL)  {
+    return TSDB_CODE_OUT_OF_MEMORY;
+  }
+
+  for (int32_t i = 0; i < numOfCols; ++i) {
+    SColMatchInfo* pColMatch = taosArrayGet(pColMatchInfo, i);
+    for (int32_t j = 0; j < pTaskInfo->schemaVer.sw->nCols; ++j) {
+      if (pColMatch->colId == pTaskInfo->schemaVer.sw->pSchema[j].colId &&
+          pColMatch->colId == PRIMARYKEY_TIMESTAMP_COL_ID) {
+        (*pSlotIds)[pColMatch->targetSlotId] = -1;
+        break;
+      }
+
+      if (pColMatch->colId == pTaskInfo->schemaVer.sw->pSchema[j].colId) {
+        (*pSlotIds)[pColMatch->targetSlotId] = j;
+        break;
+      }
+    }
+  }
+
+  return TSDB_CODE_SUCCESS;
+}
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