From 632f5fbe8f17d02c6bc04cd7bb28824c2a00e2ad Mon Sep 17 00:00:00 2001
From: wangjiaming0909 <604227650@qq.com>
Date: Thu, 3 Aug 2023 11:10:43 +0800
Subject: [PATCH] feat: optimize table merge scan when 1 child table

---
 source/libs/executor/inc/tsort.h        |  2 ++
 source/libs/executor/src/scanoperator.c | 17 +++++++++-----
 source/libs/executor/src/tsort.c        | 30 ++++++++++++++++++++++++-
 3 files changed, 42 insertions(+), 7 deletions(-)

diff --git a/source/libs/executor/inc/tsort.h b/source/libs/executor/inc/tsort.h
index 538a9f18f6..57c8bce275 100644
--- a/source/libs/executor/inc/tsort.h
+++ b/source/libs/executor/inc/tsort.h
@@ -191,6 +191,8 @@ int32_t getProperSortPageSize(size_t rowSize, uint32_t numOfCols);
 bool tsortIsClosed(SSortHandle* pHandle);
 void tsortSetClosed(SSortHandle* pHandle);
 
+void setSingleTableMerge(SSortHandle* pHandle);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/source/libs/executor/src/scanoperator.c b/source/libs/executor/src/scanoperator.c
index da4bd1e23c..399bbbf6d0 100644
--- a/source/libs/executor/src/scanoperator.c
+++ b/source/libs/executor/src/scanoperator.c
@@ -2938,17 +2938,22 @@ int32_t startGroupTableMergeScan(SOperatorInfo* pOperator) {
   // one table has one data block
   int32_t numOfTable = tableEndIdx - tableStartIdx + 1;
 
-  STableMergeScanSortSourceParam param = {0};
-  param.pOperator = pOperator;
+  STableMergeScanSortSourceParam *param = taosMemoryCalloc(1, sizeof(STableMergeScanSortSourceParam));
+  param->pOperator = pOperator;
   STableKeyInfo* startKeyInfo = tableListGetInfo(pInfo->base.pTableListInfo, tableStartIdx);
   pAPI->tsdReader.tsdReaderOpen(pHandle->vnode, &pInfo->base.cond, startKeyInfo, numOfTable, pInfo->pReaderBlock, (void**)&pInfo->base.dataReader, GET_TASKID(pTaskInfo), false, NULL);
 
   SSortSource* ps = taosMemoryCalloc(1, sizeof(SSortSource));
-  ps->param = &param;
-  ps->onlyRef = true;
+  ps->param = param;
+  ps->onlyRef = false;
   tsortAddSource(pInfo->pSortHandle, ps);
 
-  int32_t code = tsortOpen(pInfo->pSortHandle);
+  int32_t code = TSDB_CODE_SUCCESS;
+  if (numOfTable == 1) {
+    setSingleTableMerge(pInfo->pSortHandle);
+  } else {
+    code = tsortOpen(pInfo->pSortHandle);
+  }
 
   if (code != TSDB_CODE_SUCCESS) {
     T_LONG_JMP(pTaskInfo->env, terrno);
@@ -3587,4 +3592,4 @@ static void destoryTableCountScanOperator(void* param) {
 
   taosArrayDestroy(pTableCountScanInfo->stbUidList);
   taosMemoryFreeClear(param);
-}
\ No newline at end of file
+}
diff --git a/source/libs/executor/src/tsort.c b/source/libs/executor/src/tsort.c
index 0a8d7ee376..b3e562a141 100644
--- a/source/libs/executor/src/tsort.c
+++ b/source/libs/executor/src/tsort.c
@@ -69,8 +69,14 @@ struct SSortHandle {
   _sort_fetch_block_fn_t  fetchfp;
   _sort_merge_compar_fn_t comparFn;
   SMultiwayMergeTreeInfo* pMergeTree;
+
+  bool singleTableMerge;
 };
 
+void setSingleTableMerge(SSortHandle* pHandle) {
+  pHandle->singleTableMerge = true;
+}
+
 static int32_t msortComparFn(const void* pLeft, const void* pRight, void* param);
 
 // | offset[0] | offset[1] |....| nullbitmap | data |...|
@@ -1453,6 +1459,26 @@ static STupleHandle* tsortPQSortNextTuple(SSortHandle* pHandle) {
   return &pHandle->tupleHandle;
 }
 
+static STupleHandle* tsortSingleTableMergeNextTuple(SSortHandle* pHandle) {
+  if (1 == pHandle->numOfCompletedSources) return NULL;
+  if (pHandle->tupleHandle.pBlock && pHandle->tupleHandle.rowIndex + 1 < pHandle->tupleHandle.pBlock->info.rows) {
+    pHandle->tupleHandle.rowIndex++;
+  } else {
+    if (pHandle->tupleHandle.rowIndex == -1) return NULL;
+    SSortSource** pSource = taosArrayGet(pHandle->pOrderedSource, 0);
+    SSortSource*  source = *pSource;
+    SSDataBlock*  pBlock = pHandle->fetchfp(source->param);
+    if (!pBlock || pBlock->info.rows == 0) {
+      setCurrentSourceDone(source, pHandle);
+      pHandle->tupleHandle.pBlock = NULL;
+      return NULL;
+    }
+    pHandle->tupleHandle.pBlock = pBlock;
+    pHandle->tupleHandle.rowIndex = 0;
+  }
+  return &pHandle->tupleHandle;
+}
+
 int32_t tsortOpen(SSortHandle* pHandle) {
   if (pHandle->opened) {
     return 0;
@@ -1470,7 +1496,9 @@ int32_t tsortOpen(SSortHandle* pHandle) {
 }
 
 STupleHandle* tsortNextTuple(SSortHandle* pHandle) {
-  if (pHandle->pBoundedQueue)
+  if (pHandle->singleTableMerge)
+    return tsortSingleTableMergeNextTuple(pHandle);
+  else if (pHandle->pBoundedQueue)
     return tsortPQSortNextTuple(pHandle);
   else
     return tsortBufMergeSortNextTuple(pHandle);