expression: fix index out of range for AES_DECRYPT (#43086) (#43111)

* This is an automated cherry-pick of #43086

Signed-off-by: ti-chi-bot <ti-community-prow-bot@tidb.io>

* fix conflict

---------

Signed-off-by: ti-chi-bot <ti-community-prow-bot@tidb.io>
Co-authored-by: 王超 <cclcwangchao@hotmail.com>

expression/builtin_encryption_vec.go

@@ -43,6 +43,12 @@ func (b *builtinAesDecryptSig) vectorized() bool {
 
 func (b *builtinAesDecryptSig) vecEvalString(input *chunk.Chunk, result *chunk.Column) error {
 	n := input.NumRows()
+	if n == 0 {
+		// If chunk has 0 rows, just return an empty value. So we can simplify codes below it by ignoring 0 row case.
+		result.Reset(types.ETString)
+		return nil
+	}
+
 	strBuf, err := b.bufAllocator.get()
 	if err != nil {
 		return err

expression/integration_test.go

@@ -7900,3 +7900,13 @@ func TestIssue39146(t *testing.T) {
 	tk.MustExec("set @@tidb_enable_vectorized_expression = off;")
 	tk.MustQuery(`select str_to_date(substr(dest,1,6),'%H%i%s') from sun;`).Check(testkit.Rows("20:23:10"))
 }
+
+func TestAesDecryptionVecEvalWithZeroChunk(t *testing.T) {
+	// see issue: https://github.com/pingcap/tidb/issues/43063
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec("use test")
+	tk.MustExec("create table test (name1 blob,name2 blob)")
+	tk.MustExec("insert into test values(aes_encrypt('a', 'x'), aes_encrypt('b', 'x'))")
+	tk.MustQuery("SELECT * FROM test WHERE CAST(AES_DECRYPT(name1, 'x') AS CHAR) = '00' AND CAST(AES_DECRYPT(name2, 'x') AS CHAR) = '1'").Check(testkit.Rows())
+}