diff --git a/pkg/executor/internal/vecgroupchecker/vec_group_checker.go b/pkg/executor/internal/vecgroupchecker/vec_group_checker.go
index 65c2707b9722e..3def9059f508f 100644
--- a/pkg/executor/internal/vecgroupchecker/vec_group_checker.go
+++ b/pkg/executor/internal/vecgroupchecker/vec_group_checker.go
@@ -93,12 +93,12 @@ func (e *VecGroupChecker) SplitIntoGroups(chk *chunk.Chunk) (isFirstGroupSameAsP
 			return false, err
 		}
 	}
-	e.firstGroupKey, err = codec.EncodeValue(e.ctx.GetSessionVars().StmtCtx, e.firstGroupKey, e.firstRowDatums...)
+	e.firstGroupKey, err = codec.EncodeKey(e.ctx.GetSessionVars().StmtCtx, e.firstGroupKey, e.firstRowDatums...)
 	if err != nil {
 		return false, err
 	}
 
-	e.lastGroupKey, err = codec.EncodeValue(e.ctx.GetSessionVars().StmtCtx, e.lastGroupKey, e.lastRowDatums...)
+	e.lastGroupKey, err = codec.EncodeKey(e.ctx.GetSessionVars().StmtCtx, e.lastGroupKey, e.lastRowDatums...)
 	if err != nil {
 		return false, err
 	}
diff --git a/tests/integrationtest/r/executor/issues.result b/tests/integrationtest/r/executor/issues.result
index 4001bff307270..93cd6c1f9e20e 100644
--- a/tests/integrationtest/r/executor/issues.result
+++ b/tests/integrationtest/r/executor/issues.result
@@ -746,3 +746,18 @@ insert into F values (1, 8);
 select table1.`col_int` as field1, table1.`col_int` as field2 from V as table1 left join F as table2 on table1.`col_int` = table2.`col_int` order by field1, field2 desc limit 2;
 field1	field2
 8	8
+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 2b078a52e45e5..d644c6c87322c 100644
--- a/tests/integrationtest/t/executor/issues.test
+++ b/tests/integrationtest/t/executor/issues.test
@@ -557,3 +557,15 @@ create table F (id int primary key, col_int int);
 insert into F values (1, 8);
 select table1.`col_int` as field1, table1.`col_int` as field2 from V as table1 left join F as table2 on table1.`col_int` = table2.`col_int` order by field1, field2 desc limit 2;
 
+# 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