diff --git a/pkg/executor/internal/vecgroupchecker/vec_group_checker.go b/pkg/executor/internal/vecgroupchecker/vec_group_checker.go
index afa0c11a35b46..e50e35415e951 100644
--- a/pkg/executor/internal/vecgroupchecker/vec_group_checker.go
+++ b/pkg/executor/internal/vecgroupchecker/vec_group_checker.go
@@ -93,13 +93,13 @@ func (e *VecGroupChecker) SplitIntoGroups(chk *chunk.Chunk) (isFirstGroupSameAsP
 			return false, err
 		}
 	}
-	e.firstGroupKey, err = codec.EncodeValue(e.ctx.GetSessionVars().StmtCtx.TimeZone(), e.firstGroupKey, e.firstRowDatums...)
+	e.firstGroupKey, err = codec.EncodeKey(e.ctx.GetSessionVars().StmtCtx.TimeZone(), e.firstGroupKey, e.firstRowDatums...)
 	err = e.ctx.GetSessionVars().StmtCtx.HandleError(err)
 	if err != nil {
 		return false, err
 	}
 
-	e.lastGroupKey, err = codec.EncodeValue(e.ctx.GetSessionVars().StmtCtx.TimeZone(), e.lastGroupKey, e.lastRowDatums...)
+	e.lastGroupKey, err = codec.EncodeKey(e.ctx.GetSessionVars().StmtCtx.TimeZone(), e.lastGroupKey, e.lastRowDatums...)
 	err = e.ctx.GetSessionVars().StmtCtx.HandleError(err)
 	if err != nil {
 		return false, err
diff --git a/tests/integrationtest/r/executor/issues.result b/tests/integrationtest/r/executor/issues.result
index 7a564b0b06692..ae6bcdb9888bb 100644
--- a/tests/integrationtest/r/executor/issues.result
+++ b/tests/integrationtest/r/executor/issues.result
@@ -850,3 +850,18 @@ c
 2
 2147483647
 set @@sql_mode = default;
+set @@tidb_max_chunk_size = 32;
+drop table if exists t, s;
+CREATE TABLE `t` (`c` char(1)) COLLATE=utf8_general_ci  ;
+insert into t values("V"),("v");
+insert into t values("V"),("v"),("v");
+CREATE TABLE `s` (`col_61` int);
+insert into s values(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1);
+insert into s values(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1);
+SELECT /*+ stream_agg()*/ count(`t`.`c`) FROM (`s`) JOIN `t` GROUP BY `t`.`c`;
+count(`t`.`c`)
+170
+SELECT  count(`t`.`c`) FROM (`s`) JOIN `t`  GROUP BY `t`.`c`;
+count(`t`.`c`)
+170
+set @@tidb_max_chunk_size = default;
diff --git a/tests/integrationtest/t/executor/issues.test b/tests/integrationtest/t/executor/issues.test
index 52f2a7e279d2c..736464d7a2892 100644
--- a/tests/integrationtest/t/executor/issues.test
+++ b/tests/integrationtest/t/executor/issues.test
@@ -646,4 +646,17 @@ set @@sql_mode = '';
 insert into t   select round(cast('88888899999999999888888888888888888888888888888888888.11111111111111111111' as decimal(18,12)) * cast('88888899999999999888888888888888888888888888888888888.11111111111111111111' as decimal(42,18)) );
 show warnings;
 select * from t;
-set @@sql_mode = default;
\ No newline at end of file
+set @@sql_mode = default;
+
+# TestIssue49902
+set @@tidb_max_chunk_size = 32;
+drop table if exists t, s;
+CREATE TABLE `t` (`c` char(1)) COLLATE=utf8_general_ci  ;
+insert into t values("V"),("v");
+insert into t values("V"),("v"),("v");
+CREATE TABLE `s` (`col_61` int);
+insert into s values(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1);
+insert into s values(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1);
+SELECT /*+ stream_agg()*/ count(`t`.`c`) FROM (`s`) JOIN `t` GROUP BY `t`.`c`;
+SELECT  count(`t`.`c`) FROM (`s`) JOIN `t`  GROUP BY `t`.`c`;
+set @@tidb_max_chunk_size = default;
\ No newline at end of file