mysql5/mysql-5.7.27/mysql-test/t/order_by_limit.test

--echo #
--echo # WL#6986 : Make switching of index due to order by limit cost based
--echo #

--echo # Testcase for Bug#16522053

CREATE TABLE t1 (
  pk INT PRIMARY KEY AUTO_INCREMENT,
  i INT,
  j INT,
  INDEX (i),
  INDEX (j)
);

INSERT INTO t1 (i,j) VALUES (1,1);

let $1=7;
set @d=1;
while ($1)
{
  eval INSERT INTO t1 (i,j) SELECT i+@d, j+@d from t1;
  eval set @d=@d*2;
  dec $1;
}

ANALYZE TABLE t1;

let $query= SELECT * FROM t1
            WHERE i<100 AND j<10
            ORDER BY i LIMIT 5;
eval EXPLAIN $query;
eval $query;
DROP TABLE t1;

CREATE TABLE t0 (
  i0 INTEGER NOT NULL
);

INSERT INTO t0 VALUES (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);

CREATE TABLE t1 (
  pk INTEGER PRIMARY KEY,
  i1 INTEGER NOT NULL,
  i2 INTEGER NOT NULL,
  INDEX k1 (i1),
  INDEX k2 (i1,i2)
) ENGINE=InnoDB;

INSERT INTO t1
SELECT a0.i0 + 10*a1.i0 + 100*a0.i0 + 1000*a1.i0,
       (a0.i0 + 10*a1.i0 + 100*a0.i0 + 1000*a1.i0) % 1000,
       (a0.i0 + 10*a1.i0 + 100*a0.i0 + 1000*a1.i0) % 1000
FROM t0 AS a0, t0 AS a1;

CREATE TABLE t2 (
  pk INTEGER PRIMARY KEY,
  i1 INTEGER NOT NULL,
  INDEX k1 (i1)
) ENGINE=InnoDB;

INSERT INTO t2
SELECT a0.i0 + 10*a1.i0 + 100*a0.i0 + 1000*a1.i0,
              (a0.i0 + 10*a1.i0 + 100*a0.i0 + 1000*a1.i0) % 500
  FROM t0 AS a0, t0 AS a1;

ANALYZE TABLE t1,t2;

--echo # Query should use index to optimize the ORDER BY LIMIT

let query=
SELECT * FROM t1 STRAIGHT_JOIN t2 ON t1.i1=t2.i1
WHERE t1.pk > 7000 and t1.i1 > 2
ORDER BY t1.i1 LIMIT 2;

eval EXPLAIN $query;

--echo # Query should not make the switch to use index to
--echo # optimize ORDER BY LIMIT. So should be using filesort

let query=
SELECT * FROM t1 STRAIGHT_JOIN t2 ON t1.i1=t2.i1
WHERE t1.pk > 7000 and t1.i1 > 2
ORDER BY t1.i1 LIMIT 5;

eval EXPLAIN $query;
eval $query;

--echo # Changing range condition on i1 should make
--echo # key on i1 get picked to give the order

let query=
SELECT * FROM t1 STRAIGHT_JOIN t2 ON t1.i1=t2.i1
WHERE t1.pk > 7000 and t1.i1 > 800
ORDER BY t1.i1 LIMIT 5;

eval EXPLAIN $query;
eval $query;

--echo # Use range condition only on pk to see if switch
--echo # happens just for ORDER BY LIMIT
--echo # Should not happen unless range results in too
--echo # many records

let query=
SELECT * FROM t1 STRAIGHT_JOIN t2 ON t1.i1=t2.i1
WHERE t1.pk > 7000 ORDER BY t1.i1 LIMIT 5;

eval EXPLAIN $query;
eval $query;

let query=
SELECT * FROM t1 STRAIGHT_JOIN t2 ON t1.i1=t2.i1
WHERE t1.pk > 1000 ORDER BY t1.i1 LIMIT 5;

eval EXPLAIN $query;
eval $query;

--echo # check if switch happens when the index for order 
--echo # by is non-covering

let query=
SELECT t1.i1,t1.i2 FROM t1 STRAIGHT_JOIN t2 ON t1.i1=t2.i1 
WHERE t1.pk > 100 ORDER BY t1.i1 LIMIT 5;

eval EXPLAIN $query;
eval $query;

--echo # Reduce the fanout for table t2 and check
--echo # that index for order by is not choosen

let query=
SELECT * FROM t1 STRAIGHT_JOIN t2 ON t1.i1=t2.i1
WHERE t1.pk > 7000 and t2.pk = 100 ORDER BY t1.i1 LIMIT 5;

eval EXPLAIN $query;
eval $query;

--echo # Increase the fanout to see if index gets choosen
--echo # for order by for which range scan was choosen
--echo # earlier

INSERT INTO t2
SELECT a0.i0 + 10*a1.i0 + 100*a0.i0 + 1000*a1.i0 + 1,
              (a0.i0 + 10*a1.i0 + 100*a0.i0 + 1000*a1.i0) % 500
  FROM t0 AS a0, t0 AS a1;

ANALYZE TABLE t2;

let query=
SELECT * FROM t1 STRAIGHT_JOIN t2 ON t1.i1=t2.i1
WHERE t1.pk > 7000 ORDER BY t1.i1 LIMIT 5;

eval EXPLAIN $query;
eval $query;

--echo # Check if the index for order by is used when
--echo # force index is done on order by

let query=
SELECT * FROM t1 FORCE INDEX FOR ORDER BY (k2) STRAIGHT_JOIN t2 ON
t1.i1=t2.i1 WHERE t1.pk > 7000 ORDER BY t1.i1 LIMIT 5;

eval EXPLAIN $query;
eval $query;

DROP TABLE t0, t1, t2;