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#
# MDEV-32351: Significant slowdown for query with many outer joins
#
CREATE TABLE t1 (b int NOT NULL, PRIMARY KEY (b)) ENGINE=MYISAM;
INSERT INTO t1 select seq from seq_1_to_10000;
CREATE TABLE t2 (b int NOT NULL, d varchar(255), KEY (b)) ENGINE=MYISAM ;
INSERT INTO t2 VALUES (1,1),(2,2),(3,3);
CREATE TABLE t3 (c int NOT NULL, PRIMARY KEY (c)) ENGINE=MYISAM ;
INSERT INTO t3 select seq from seq_1_to_3000;
CREATE TABLE t4 (c int NOT NULL, PRIMARY KEY (c)) ENGINE=MYISAM;
INSERT INTO t4 select seq from seq_1_to_3000;
ANALYZE TABLE t1,t2,t3,t4;
Table Op Msg_type Msg_text
test.t1 analyze status Engine-independent statistics collected
test.t1 analyze status OK
test.t2 analyze status Engine-independent statistics collected
test.t2 analyze status OK
test.t3 analyze status Engine-independent statistics collected
test.t3 analyze status OK
test.t4 analyze status Engine-independent statistics collected
test.t4 analyze status OK
create table t1_t2 as
select
t1.b as t1_b, t2.b as t2_b, t2.d as t2_d
FROM t1
LEFT JOIN t2 ON t1.b = t2.b;
SET statement debug_dbug='+d,analyze_print_r_unpack_ops' for
analyze
format=json
SELECT COUNT(*)
FROM t1_t2
LEFT JOIN t3 ON t2_d = t3.c
LEFT JOIN t4 ON t3.c=1
select '$js' as JSON;
JSON
{
"query_optimization": {
"r_total_time_ms": "REPLACED"
},
"query_block": {
"select_id": 1,
"cost": "REPLACED",
"r_loops": 1,
"r_total_time_ms": "REPLACED",
"const_condition": "1",
"nested_loop": [
{
"table": {
"table_name": "t1_t2",
"access_type": "ALL",
"loops": 1,
"r_loops": 1,
"rows": 10000,
"r_rows": 10000,
"cost": "REPLACED",
"r_table_time_ms": "REPLACED",
"r_other_time_ms": "REPLACED",
"r_engine_stats": REPLACED,
"filtered": 100,
"r_total_filtered": 100,
"r_filtered": 100
}
},
{
"table": {
"table_name": "t3",
"access_type": "eq_ref",
"possible_keys": ["PRIMARY"],
"key": "PRIMARY",
"key_length": "4",
"used_key_parts": ["c"],
"ref": ["test.t1_t2.t2_d"],
"loops": 10000,
"r_loops": 10000,
"r_table_loops": 3,
"rows": 1,
"r_rows": 0.0003,
"cost": "REPLACED",
"r_table_time_ms": "REPLACED",
"r_other_time_ms": "REPLACED",
"r_engine_stats": REPLACED,
"filtered": 100,
"r_total_filtered": 100,
"attached_condition": "trigcond(t1_t2.t2_d = t3.c and trigcond(t1_t2.t2_d is not null))",
"r_filtered": 100,
"using_index": true
}
},
{
"block-nl-join": {
"table": {
"table_name": "t4",
"access_type": "index",
"key": "PRIMARY",
"key_length": "4",
"used_key_parts": ["c"],
"loops": 10000,
"r_loops": 1,
"rows": 3000,
"r_rows": 3000,
"cost": "REPLACED",
"r_table_time_ms": "REPLACED",
"r_other_time_ms": "REPLACED",
"r_engine_stats": REPLACED,
"filtered": 100,
"r_total_filtered": 100,
"r_filtered": 100,
"using_index": true
},
"buffer_type": "flat",
"buffer_size": "256Kb",
"join_type": "BNL",
"attached_condition": "trigcond(trigcond(t3.c = 1))",
"r_loops": 10000,
"r_filtered": 0.04333,
"r_unpack_time_ms": "REPLACED",
"r_unpack_ops": 3000,
"r_other_time_ms": "REPLACED",
"r_effective_rows": 3000
}
}
]
}
}
# This must show 3000, not 30000000:
select json_extract('$js', '\$**.r_unpack_ops') as R_UNPACK_OPS;
R_UNPACK_OPS
[3000]
SET debug_dbug=@old_debug;
drop table t1,t2,t3,t4;
drop table t1_t2;
|
