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MDEV-7860: EXPLAIN FORMAT=JSON crashes for loose scan query
(Based on original patch by Sanja Byelkin) Make the code that produces JSON output handle LooseScan quick select. The output we produce is compatible with MySQL 5.6.
This commit is contained in:
Sergei Petrunia
@ -906,3 +906,142 @@ id select_type table type possible_keys key key_len ref rows Extra
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3 UNION NULL NULL NULL NULL NULL NULL NULL No tables used
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NULL UNION RESULT <union2,3> ALL NULL NULL NULL NULL NULL
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DROP TABLE t1;
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#
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# MDEV-7860: EXPLAIN FORMAT=JSON crashes for loose scan query
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#
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create table t2(a int);
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insert into t2 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
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create table t1 (a int, b int, c int, d int, key(a,b,c));
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insert into t1 select A.a, B.a, C.a, D.a from t2 A, t2 B, t2 C, t2 D;
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explain select count(distinct b) from t1 group by a;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 range NULL a 10 NULL 101 Using index for group-by
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explain format=json select count(distinct b) from t1 group by a;
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EXPLAIN
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{
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"query_block": {
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"select_id": 1,
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"table": {
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"table_name": "t1",
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"access_type": "range",
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"key": "a",
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"key_length": "10",
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"used_key_parts": ["a", "b"],
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"rows": 101,
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"filtered": 100,
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"using_index_for_group_by": true
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}
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}
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}
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analyze format=json select count(distinct b) from t1 group by a;
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ANALYZE
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{
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"query_block": {
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"select_id": 1,
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"r_loops": 1,
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"r_total_time_ms": "REPLACED",
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"table": {
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"table_name": "t1",
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"access_type": "range",
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"key": "a",
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"key_length": "10",
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"used_key_parts": ["a", "b"],
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"r_loops": 1,
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"rows": 101,
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"r_rows": 100,
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"r_total_time_ms": "REPLACED",
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"filtered": 100,
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"r_filtered": 100,
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"using_index_for_group_by": true
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}
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}
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}
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drop table t1,t2;
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#
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# Try both variants of LooseScan (data/queries borrowed from group_min_max.test)
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#
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create table t1 (
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a1 char(64), a2 char(64), b char(16), c char(16) not null, d char(16), dummy char(248) default ' '
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);
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insert into t1 (a1, a2, b, c, d) values
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('a','a','a','a111','xy1'),('a','a','a','b111','xy2'),('a','a','a','c111','xy3'),('a','a','a','d111','xy4'),
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('a','a','b','e112','xy1'),('a','a','b','f112','xy2'),('a','a','b','g112','xy3'),('a','a','b','h112','xy4'),
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('a','b','a','i121','xy1'),('a','b','a','j121','xy2'),('a','b','a','k121','xy3'),('a','b','a','l121','xy4'),
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('a','b','b','m122','xy1'),('a','b','b','n122','xy2'),('a','b','b','o122','xy3'),('a','b','b','p122','xy4'),
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('b','a','a','a211','xy1'),('b','a','a','b211','xy2'),('b','a','a','c211','xy3'),('b','a','a','d211','xy4'),
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('b','a','b','e212','xy1'),('b','a','b','f212','xy2'),('b','a','b','g212','xy3'),('b','a','b','h212','xy4'),
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('b','b','a','i221','xy1'),('b','b','a','j221','xy2'),('b','b','a','k221','xy3'),('b','b','a','l221','xy4'),
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('b','b','b','m222','xy1'),('b','b','b','n222','xy2'),('b','b','b','o222','xy3'),('b','b','b','p222','xy4'),
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('c','a','a','a311','xy1'),('c','a','a','b311','xy2'),('c','a','a','c311','xy3'),('c','a','a','d311','xy4'),
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('c','a','b','e312','xy1'),('c','a','b','f312','xy2'),('c','a','b','g312','xy3'),('c','a','b','h312','xy4'),
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('c','b','a','i321','xy1'),('c','b','a','j321','xy2'),('c','b','a','k321','xy3'),('c','b','a','l321','xy4'),
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('c','b','b','m322','xy1'),('c','b','b','n322','xy2'),('c','b','b','o322','xy3'),('c','b','b','p322','xy4'),
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('d','a','a','a411','xy1'),('d','a','a','b411','xy2'),('d','a','a','c411','xy3'),('d','a','a','d411','xy4'),
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('d','a','b','e412','xy1'),('d','a','b','f412','xy2'),('d','a','b','g412','xy3'),('d','a','b','h412','xy4'),
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('d','b','a','i421','xy1'),('d','b','a','j421','xy2'),('d','b','a','k421','xy3'),('d','b','a','l421','xy4'),
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('d','b','b','m422','xy1'),('d','b','b','n422','xy2'),('d','b','b','o422','xy3'),('d','b','b','p422','xy4'),
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('a','a','a','a111','xy1'),('a','a','a','b111','xy2'),('a','a','a','c111','xy3'),('a','a','a','d111','xy4'),
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('a','a','b','e112','xy1'),('a','a','b','f112','xy2'),('a','a','b','g112','xy3'),('a','a','b','h112','xy4'),
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('a','b','a','i121','xy1'),('a','b','a','j121','xy2'),('a','b','a','k121','xy3'),('a','b','a','l121','xy4'),
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('a','b','b','m122','xy1'),('a','b','b','n122','xy2'),('a','b','b','o122','xy3'),('a','b','b','p122','xy4'),
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('b','a','a','a211','xy1'),('b','a','a','b211','xy2'),('b','a','a','c211','xy3'),('b','a','a','d211','xy4'),
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('b','a','b','e212','xy1'),('b','a','b','f212','xy2'),('b','a','b','g212','xy3'),('b','a','b','h212','xy4'),
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('b','b','a','i221','xy1'),('b','b','a','j221','xy2'),('b','b','a','k221','xy3'),('b','b','a','l221','xy4'),
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('b','b','b','m222','xy1'),('b','b','b','n222','xy2'),('b','b','b','o222','xy3'),('b','b','b','p222','xy4'),
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('c','a','a','a311','xy1'),('c','a','a','b311','xy2'),('c','a','a','c311','xy3'),('c','a','a','d311','xy4'),
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('c','a','b','e312','xy1'),('c','a','b','f312','xy2'),('c','a','b','g312','xy3'),('c','a','b','h312','xy4'),
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('c','b','a','i321','xy1'),('c','b','a','j321','xy2'),('c','b','a','k321','xy3'),('c','b','a','l321','xy4'),
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('c','b','b','m322','xy1'),('c','b','b','n322','xy2'),('c','b','b','o322','xy3'),('c','b','b','p322','xy4'),
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('d','a','a','a411','xy1'),('d','a','a','b411','xy2'),('d','a','a','c411','xy3'),('d','a','a','d411','xy4'),
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('d','a','b','e412','xy1'),('d','a','b','f412','xy2'),('d','a','b','g412','xy3'),('d','a','b','h412','xy4'),
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('d','b','a','i421','xy1'),('d','b','a','j421','xy2'),('d','b','a','k421','xy3'),('d','b','a','l421','xy4'),
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('d','b','b','m422','xy1'),('d','b','b','n422','xy2'),('d','b','b','o422','xy3'),('d','b','b','p422','xy4');
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create index idx_t1_0 on t1 (a1);
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create index idx_t1_1 on t1 (a1,a2,b,c);
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create index idx_t1_2 on t1 (a1,a2,b);
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analyze table t1;
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Table Op Msg_type Msg_text
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test.t1 analyze status Table is already up to date
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explain select count(distinct a1,a2,b) from t1 where (a2 >= 'b') and (b = 'a');
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 range NULL idx_t1_1 147 NULL 17 Using where; Using index for group-by
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explain select count(distinct a1,a2,b,c) from t1 where (a2 >= 'b') and (b = 'a') and (c = 'i121');
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 range NULL idx_t1_1 163 NULL 65 Using where; Using index for group-by (scanning)
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explain format=json select count(distinct a1,a2,b) from t1 where (a2 >= 'b') and (b = 'a');
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EXPLAIN
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{
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"query_block": {
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"select_id": 1,
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"table": {
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"table_name": "t1",
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"access_type": "range",
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"key": "idx_t1_1",
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"key_length": "147",
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"used_key_parts": ["a1", "a2", "b"],
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"rows": 17,
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"filtered": 100,
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"attached_condition": "((t1.b = 'a') and (t1.a2 >= 'b'))",
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"using_index_for_group_by": true
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}
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}
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}
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explain format=json select count(distinct a1,a2,b,c) from t1 where (a2 >= 'b') and (b = 'a') and (c = 'i121');
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EXPLAIN
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{
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"query_block": {
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"select_id": 1,
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"table": {
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"table_name": "t1",
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"access_type": "range",
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"key": "idx_t1_1",
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"key_length": "163",
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"used_key_parts": ["a1", "a2", "b", "c"],
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"rows": 65,
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"filtered": 100,
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"attached_condition": "((t1.b = 'a') and (t1.c = 'i121') and (t1.a2 >= 'b'))",
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"using_index_for_group_by": "scanning"
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}
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}
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}
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drop table t1;
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