From 96bcd5c26f2d22eadbcfcd8b43cb15c7daea56a4 Mon Sep 17 00:00:00 2001
From: Hongze Cheng <hzcheng@taosdata.com>
Date: Fri, 25 Dec 2020 02:29:43 +0000
Subject: [PATCH] implement get cached last row function

---
 src/tsdb/src/tsdbRead.c | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/src/tsdb/src/tsdbRead.c b/src/tsdb/src/tsdbRead.c
index a7af44b1ee..e79b033d32 100644
--- a/src/tsdb/src/tsdbRead.c
+++ b/src/tsdb/src/tsdbRead.c
@@ -2183,8 +2183,25 @@ bool tsdbNextDataBlock(TsdbQueryHandleT* pHandle) {
   return ret;
 }
 
-int32_t tsdbGetCachedLastRow(STable* pTable, void** pRes) {
-  return 0;
+/*
+ * 1. no data at all (pTable->lastKey = TSKEY_INITIAL_VAL), just return TSKEY_INITIAL_VAL
+ * 2. has data but not loaded, just return lastKey but not set pRes
+ * 3. has data and loaded, return lastKey and set pRes
+ */
+TSKEY tsdbGetCachedLastRow(STable* pTable, void** pRes) {
+  TSKEY lastKey;
+
+  TSDB_RLOCK_TABLE(pTable);
+  lastKey = pTable->lastKey;
+
+  if (lastKey != TSKEY_INITIAL_VAL && pTable->lastRow) {
+    *pRes = tdDataRowDup(pTable->lastRow);
+    if (*pRes == NULL) {
+      // TODO: handle error
+    }
+  }
+  TSDB_RUNLOCK_TABLE(pTable);
+  return lastKey;
 }
 
 void checkCachedLastRow(STsdbQueryHandle* pQueryHandle, STableGroupInfo *groupList) {
-- 
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