set @@global.tidb_scatter_region='table';
drop table if exists t;
set tidb_enable_clustered_index = on;
create table t (a varchar(255) primary key, b bigint);
insert into t values ('b', 100), ('y', 100);
split table t between ('a') and ('z') regions 2;
TOTAL_SPLIT_REGION	SCATTER_FINISH_RATIO
1	1
select a from t tablesample regions();
a
b
y
drop table t;
create table t (a varchar(255), b int, c decimal, primary key (a, b, c));
split table t between ('a', 0, 0) and ('z', 100, 100) regions 2;
TOTAL_SPLIT_REGION	SCATTER_FINISH_RATIO
1	1
insert into t values ('b', 10, 100), ('y', 100, 10);
select * from t tablesample regions();
a	b	c
b	10	100
y	100	10
drop table t;
create table t (a bigint primary key, b int default 10);
split table t between (1) and (100000) regions 4;
TOTAL_SPLIT_REGION	SCATTER_FINISH_RATIO
3	1
insert into t(a) values (200), (25600), (50300), (99900), (99901);
select a from t tablesample regions();
a
200
25600
50300
99900
drop table t;
create table t (a bigint, b int default 10);
split table t between (0) and (100000) regions 4;
TOTAL_SPLIT_REGION	SCATTER_FINISH_RATIO
3	1
insert into t(a) values (1), (2), (3);
select a from t tablesample regions();
a
1
set tidb_enable_clustered_index=default;
drop table if exists t;
create table t (a int, b varchar(255));
insert into t values (1, 'abc');
create view v as select * from t;
select * from v tablesample regions();
Error 8128 (HY000): Invalid TABLESAMPLE: Unsupported TABLESAMPLE in views
select * from information_schema.tables tablesample regions();
Error 8128 (HY000): Invalid TABLESAMPLE: Unsupported TABLESAMPLE in virtual tables
select a from t tablesample system();
Error 8128 (HY000): Invalid TABLESAMPLE: Only supports REGIONS sampling method
select a from t tablesample bernoulli(10 percent);
Error 8128 (HY000): Invalid TABLESAMPLE: Only supports REGIONS sampling method
select a from t as t1 tablesample regions(), t as t2 tablesample system();
Error 8128 (HY000): Invalid TABLESAMPLE: Only supports REGIONS sampling method
select a from t tablesample ();
Error 8128 (HY000): Invalid TABLESAMPLE: Only supports REGIONS sampling method
drop table if exists t;
create table t (a int, b varchar(255));
insert into t values (1, 'abc');
select _tidb_rowid from t tablesample regions();
_tidb_rowid
1
select a, _tidb_rowid from t tablesample regions();
a	_tidb_rowid
1	1
select _tidb_rowid, b from t tablesample regions();
_tidb_rowid	b
1	abc
select b, _tidb_rowid, a from t tablesample regions();
b	_tidb_rowid	a
abc	1	1
drop table if exists t;
create table t (a int, b varchar(255), primary key (a)) partition by hash(a) partitions 2;
insert into t values (1, '1'), (2, '2'), (3, '3');
select count(*) from t tablesample regions();
count(*)
2
delete from t;
insert into t values (1, '1');
select count(*) from t partition (p0) tablesample regions();
count(*)
0
select count(*) from t partition (p1) tablesample regions();
count(*)
1
drop table if exists t;
create table t (a int, b int, unique key idx(a)) partition by range (a) (
partition p0 values less than (0),
partition p1 values less than (10),
partition p2 values less than (30),
partition p3 values less than (maxvalue));
insert into t values (2, 2), (31, 31), (12, 12);
select _tidb_rowid from t tablesample regions() order by _tidb_rowid;
_tidb_rowid
1
2
3
drop table if exists t;
create table t (a int primary key, b int as (a + 1), c int as (b + 1), d int as (c + 1));
split table t between (0) and (10000) regions 4;
TOTAL_SPLIT_REGION	SCATTER_FINISH_RATIO
3	1
insert into t(a) values (1), (2), (2999), (4999), (9999);
select a from t tablesample regions();
a
1
2999
9999
select c from t tablesample regions();
c
3
3001
10001
select a, b from t tablesample regions();
a	b
1	2
2999	3000
9999	10000
select d, c from t tablesample regions();
d	c
4	3
3002	3001
10002	10001
select a, d from t tablesample regions();
a	d
1	4
2999	3002
9999	10002
drop table if exists t;
create table t (a int primary key);
split table t between (0) and (40000) regions 4;
TOTAL_SPLIT_REGION	SCATTER_FINISH_RATIO
3	1
insert into t values (1), (1000), (10002);
select * from t tablesample regions();
a
1
10002
begin;
insert into t values (20006), (50000);
select * from t tablesample regions();
a
1
10002
delete from t where a = 1;
select * from t tablesample regions();
a
1
10002
commit;
select * from t tablesample regions();
a
1000
10002
20006
50000
drop table if exists t;
create table t (a int primary key);
split table t between (0) and (40000) regions 4;
TOTAL_SPLIT_REGION	SCATTER_FINISH_RATIO
3	1
insert into t values (1), (1000), (10002);
begin;
select * from t tablesample regions();
a
1
10002
insert into t values (20006), (50000);
select * from t tablesample regions();
a
1
10002
commit;
select * from t tablesample regions();
a
1
10002
20006
50000
drop table if exists t;
create table t (a int primary key, b int, c varchar(255));
split table t between (0) and (10000) regions 5;
TOTAL_SPLIT_REGION	SCATTER_FINISH_RATIO
4	1
insert into t values (1000, 1, '1'), (1001, 1, '1'), (2100, 2, '2'), (4500, 3, '3');
create index idx_0 on t (b);
select a from t tablesample regions() order by a;
a
1000
2100
4500
select a from t use index (idx_0) tablesample regions() order by a;
Error 1815 (HY000): Internal : Can't find a proper physical plan for this query
DROP TABLE IF EXISTS a;
CREATE TABLE a (pk bigint unsigned primary key clustered, v text);
INSERT INTO a WITH RECURSIVE b(pk) AS (SELECT 1 UNION ALL SELECT pk+1 FROM b WHERE pk < 1000) SELECT pk, 'a' FROM b;
INSERT INTO a WITH RECURSIVE b(pk) AS (SELECT 1 UNION ALL SELECT pk+1 FROM b WHERE pk < 1000) SELECT pk + (1<<63), 'b' FROM b;
SPLIT TABLE a BY (500);
TOTAL_SPLIT_REGION	SCATTER_FINISH_RATIO
1	1
SELECT * FROM a TABLESAMPLE REGIONS() ORDER BY pk;
pk	v
500	a
9223372036854775809	b
set @@global.tidb_scatter_region=default;
drop table if exists t;
create table t (a int, b varchar(255), primary key (a)) partition by hash(a) partitions 2;
insert into t values (1, '1'), (2, '2'), (3, '3');
select sleep(0.5);
sleep(0.5)
0
set @@tidb_partition_prune_mode='static';
select * from t tablesample regions() order by a;
a	b
1	1
2	2
set @@tidb_partition_prune_mode='dynamic';
select * from t tablesample regions() order by a;
a	b
1	1
2	2
set @@tidb_partition_prune_mode=default;
drop table if exists t;
create table t (a decimal(62,2) not null, key idx (a), primary key (a) clustered);
select a from t tablesample regions() order by a;
a