[UT] mark the test case test_table_sample sequential

test/sql/test_scan/R/test_table_sample

@@ -1,4 +1,4 @@
--- name: test_table_sample
+-- name: test_table_sample @sequential
 set pipeline_dop = 1;
 -- result:
 -- !result
@@ -25,6 +25,10 @@ alter table t1 compact;
 alter table pk_t1 compact;
 -- result:
 -- !result
+select sleep(3);
+-- result:
+1
+-- !result
 select count(k1), sum(k1), sum(k2) from t1 sample('method'='by_nothing');
 -- result:
 E: (1064, 'Getting syntax error from line 1, column 43 to line 1, column 71. Detail message: unrecognized sample-method: by_nothing.')

test/sql/test_scan/T/test_table_sample

@@ -1,4 +1,4 @@
--- name: test_table_sample
+-- name: test_table_sample @sequential
 
 set pipeline_dop = 1;
 
@@ -16,8 +16,10 @@ select s1, s1 % 1000, repeat('a', 128) FROM TABLE(generate_series(1, 655350)) s(
 
 create table pk_t1 primary key(k1) as select * from t1;
 
+-- make sure all data are compacted into one segment, otherwise the sample result is not stable
 alter table t1 compact;
 alter table pk_t1 compact;
+select sleep(3);
 
 -- arguments
 select count(k1), sum(k1), sum(k2) from t1 sample('method'='by_nothing');