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MDEV-10372: EXPLAIN fixes for recursive CTEs, including FORMAT=JSON

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- Tabular EXPLAIN now prints "RECURSIVE UNION".
- There is a basic implementation of EXPLAIN FORMAT=JSON.
- it produces "recursive_union" JSON struct
- No other details or ANALYZE support, yet.
This commit is contained in:
Sergei Petrunia
2016-08-08 23:02:52 +03:00
parent e1c92a6ca9
commit a2f245e49f
8 changed files with 493 additions and 17 deletions
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366
mysql-test/r/cte_recursive.result
View File

@ -115,8 +115,8 @@ select * from t1;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY <derived2> ALL NULL NULL NULL NULL 5
2 SUBQUERY t2 ALL NULL NULL NULL NULL 5 Using where
3 UNCACHEABLE UNION <derived2> ALL NULL NULL NULL NULL 5
3 UNCACHEABLE UNION t2 ALL NULL NULL NULL NULL 5 Using where; Using join buffer (flat, BNL join)
3 RECURSIVE UNION <derived2> ALL NULL NULL NULL NULL 5
3 RECURSIVE UNION t2 ALL NULL NULL NULL NULL 5 Using where; Using join buffer (flat, BNL join)
NULL UNION RESULT <union2,3> ALL NULL NULL NULL NULL NULL
# just WITH : types of t1 columns are determined by all parts of union
create view v1 as
@ -599,10 +599,10 @@ id select_type table type possible_keys key key_len ref rows filtered Extra
1 PRIMARY <derived3> ref key0 key0 5 c.h_id 2 100.00
1 PRIMARY <derived3> ref key0 key0 5 c.w_id 2 100.00
3 SUBQUERY folks ALL NULL NULL NULL NULL 12 100.00 Using where
4 UNCACHEABLE UNION <derived2> ALL NULL NULL NULL NULL 2 100.00
4 UNCACHEABLE UNION p ALL NULL NULL NULL NULL 12 100.00 Using where; Using join buffer (flat, BNL join)
5 UNCACHEABLE UNION <derived2> ALL NULL NULL NULL NULL 2 100.00
5 UNCACHEABLE UNION p ALL NULL NULL NULL NULL 12 100.00 Using where; Using join buffer (flat, BNL join)
4 RECURSIVE UNION <derived2> ALL NULL NULL NULL NULL 2 100.00
4 RECURSIVE UNION p ALL NULL NULL NULL NULL 12 100.00 Using where; Using join buffer (flat, BNL join)
5 RECURSIVE UNION <derived2> ALL NULL NULL NULL NULL 2 100.00
5 RECURSIVE UNION p ALL NULL NULL NULL NULL 12 100.00 Using where; Using join buffer (flat, BNL join)
NULL UNION RESULT <union3,4,5> ALL NULL NULL NULL NULL NULL NULL
2 UNCACHEABLE SUBQUERY <derived3> ALL NULL NULL NULL NULL 12 100.00 Using where
Warnings:
@ -781,8 +781,8 @@ select * from ancestors;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 PRIMARY <derived2> ALL NULL NULL NULL NULL 12 100.00
2 SUBQUERY folks ALL NULL NULL NULL NULL 12 100.00 Using where
3 UNCACHEABLE UNION p ALL NULL NULL NULL NULL 12 100.00
3 UNCACHEABLE UNION <derived2> ALL NULL NULL NULL NULL 12 100.00 Using where; Using join buffer (flat, BNL join)
3 RECURSIVE UNION p ALL NULL NULL NULL NULL 12 100.00
3 RECURSIVE UNION <derived2> ALL NULL NULL NULL NULL 12 100.00 Using where; Using join buffer (flat, BNL join)
NULL UNION RESULT <union2,3> ALL NULL NULL NULL NULL NULL NULL
Warnings:
Note 1003 with recursive ancestors as (select `test`.`folks`.`id` AS `id`,`test`.`folks`.`name` AS `name`,`test`.`folks`.`dob` AS `dob`,`test`.`folks`.`father` AS `father`,`test`.`folks`.`mother` AS `mother` from `test`.`folks` where ((`test`.`folks`.`name` = 'Me') and (`test`.`folks`.`dob` = DATE'2000-01-01')) union select `p`.`id` AS `id`,`p`.`name` AS `name`,`p`.`dob` AS `dob`,`p`.`father` AS `father`,`p`.`mother` AS `mother` from `test`.`folks` `p` join `ancestors` `a` where ((`a`.`father` = `p`.`id`) or (`a`.`mother` = `p`.`id`)))select `ancestors`.`id` AS `id`,`ancestors`.`name` AS `name`,`ancestors`.`dob` AS `dob`,`ancestors`.`father` AS `father`,`ancestors`.`mother` AS `mother` from `ancestors`
@ -1137,10 +1137,10 @@ select * from ancestors;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY <derived2> ALL NULL NULL NULL NULL 12
2 SUBQUERY folks ALL NULL NULL NULL NULL 12 Using where
3 UNCACHEABLE UNION p ALL PRIMARY NULL NULL NULL 12
3 UNCACHEABLE UNION <derived2> ref key0 key0 5 test.p.id 2
4 UNCACHEABLE UNION p ALL PRIMARY NULL NULL NULL 12
4 UNCACHEABLE UNION <derived2> ref key0 key0 5 test.p.id 2
3 RECURSIVE UNION p ALL PRIMARY NULL NULL NULL 12
3 RECURSIVE UNION <derived2> ref key0 key0 5 test.p.id 2
4 RECURSIVE UNION p ALL PRIMARY NULL NULL NULL 12
4 RECURSIVE UNION <derived2> ref key0 key0 5 test.p.id 2
NULL UNION RESULT <union2,3,4> ALL NULL NULL NULL NULL NULL
with recursive
ancestors
@ -1168,4 +1168,346 @@ id name dob father mother
9 Grandma Ann 1941-10-15 NULL NULL
7 Grandma Sally 1943-08-23 NULL 6
6 Grandgrandma Martha 1923-05-17 NULL NULL
#
# EXPLAIN FORMAT=JSON on a query where one recursive CTE uses another:
#
explain
with recursive
prev_gen
as
(
select folks.*
from folks, prev_gen
where folks.id=prev_gen.father or folks.id=prev_gen.mother
union
select *
from folks
where name='Me'
),
ancestors
as
(
select *
from folks
where name='Me'
union
select *
from ancestors
union
select *
from prev_gen
)
select ancestors.name, ancestors.dob from ancestors;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY <derived4> ALL NULL NULL NULL NULL 24
4 SUBQUERY folks ALL NULL NULL NULL NULL 12 Using where
6 RECURSIVE UNION <derived3> ALL NULL NULL NULL NULL 12
5 RECURSIVE UNION <derived4> ALL NULL NULL NULL NULL 24
NULL UNION RESULT <union4,6,5> ALL NULL NULL NULL NULL NULL
3 SUBQUERY folks ALL NULL NULL NULL NULL 12 Using where
2 RECURSIVE UNION folks ALL PRIMARY NULL NULL NULL 12
2 RECURSIVE UNION <derived3> ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
NULL UNION RESULT <union3,2> ALL NULL NULL NULL NULL NULL
explain FORMAT=JSON
with recursive
prev_gen
as
(
select folks.*
from folks, prev_gen
where folks.id=prev_gen.father or folks.id=prev_gen.mother
union
select *
from folks
where name='Me'
),
ancestors
as
(
select *
from folks
where name='Me2'
union
select *
from ancestors where id < 234
union
select *
from prev_gen where id < 345
)
select ancestors.name, ancestors.dob from ancestors;
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"table_name": "<derived4>",
"access_type": "ALL",
"rows": 24,
"filtered": 100,
"materialized": {
"query_block": {
"recursive_union": {
"table_name": "<union4,6,5>",
"access_type": "ALL",
"query_specifications": [
{
"query_block": {
"select_id": 4,
"table": {
"table_name": "folks",
"access_type": "ALL",
"rows": 12,
"filtered": 100,
"attached_condition": "(folks.`name` = 'Me2')"
}
}
},
{
"query_block": {
"select_id": 6,
"table": {
"table_name": "<derived3>",
"access_type": "ALL",
"rows": 12,
"filtered": 100,
"attached_condition": "(prev_gen.`id` < 345)",
"materialized": {
"query_block": {
"recursive_union": {
"table_name": "<union3,2>",
"access_type": "ALL",
"query_specifications": [
{
"query_block": {
"select_id": 3,
"table": {
"table_name": "folks",
"access_type": "ALL",
"rows": 12,
"filtered": 100,
"attached_condition": "(folks.`name` = 'Me')"
}
}
},
{
"query_block": {
"select_id": 2,
"table": {
"table_name": "folks",
"access_type": "ALL",
"possible_keys": ["PRIMARY"],
"rows": 12,
"filtered": 100
},
"block-nl-join": {
"table": {
"table_name": "<derived3>",
"access_type": "ALL",
"rows": 12,
"filtered": 100
},
"buffer_type": "flat",
"buffer_size": "256Kb",
"join_type": "BNL",
"attached_condition": "((prev_gen.father = folks.`id`) or (prev_gen.mother = folks.`id`))"
}
}
}
]
}
}
}
}
}
},
{
"query_block": {
"select_id": 5,
"table": {
"table_name": "<derived4>",
"access_type": "ALL",
"rows": 24,
"filtered": 100,
"attached_condition": "(ancestors.`id` < 234)"
}
}
}
]
}
}
}
}
}
}
#
explain format=json
with recursive
ancestor_couples(h_id, h_name, h_dob, h_father, h_mother,
w_id, w_name, w_dob, w_father, w_mother)
as
(
select h.*, w.*
from folks h, folks w, coupled_ancestors a
where a.father = h.id AND a.mother = w.id
union
select h.*, w.*
from folks v, folks h, folks w
where v.name = 'Me' and
(v.father = h.id AND v.mother= w.id)
),
coupled_ancestors (id, name, dob, father, mother)
as
(
select h_id, h_name, h_dob, h_father, h_mother
from ancestor_couples
union all
select w_id, w_name, w_dob, w_father, w_mother
from ancestor_couples
)
select h_name, h_dob, w_name, w_dob
from ancestor_couples;
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"table_name": "<derived3>",
"access_type": "ALL",
"rows": 12,
"filtered": 100,
"materialized": {
"query_block": {
"recursive_union": {
"table_name": "<union3,2>",
"access_type": "ALL",
"query_specifications": [
{
"query_block": {
"select_id": 3,
"table": {
"table_name": "v",
"access_type": "ALL",
"rows": 12,
"filtered": 100,
"attached_condition": "((v.`name` = 'Me') and (v.father is not null) and (v.mother is not null))"
},
"table": {
"table_name": "h",
"access_type": "eq_ref",
"possible_keys": ["PRIMARY"],
"key": "PRIMARY",
"key_length": "4",
"used_key_parts": ["id"],
"ref": ["test.v.father"],
"rows": 1,
"filtered": 100
},
"table": {
"table_name": "w",
"access_type": "eq_ref",
"possible_keys": ["PRIMARY"],
"key": "PRIMARY",
"key_length": "4",
"used_key_parts": ["id"],
"ref": ["test.v.mother"],
"rows": 1,
"filtered": 100
}
}
},
{
"query_block": {
"select_id": 2,
"table": {
"table_name": "<derived4>",
"access_type": "ALL",
"rows": 2,
"filtered": 100,
"attached_condition": "((a.father is not null) and (a.mother is not null))"
},
"table": {
"table_name": "h",
"access_type": "eq_ref",
"possible_keys": ["PRIMARY"],
"key": "PRIMARY",
"key_length": "4",
"used_key_parts": ["id"],
"ref": ["a.father"],
"rows": 1,
"filtered": 100
},
"table": {
"table_name": "w",
"access_type": "eq_ref",
"possible_keys": ["PRIMARY"],
"key": "PRIMARY",
"key_length": "4",
"used_key_parts": ["id"],
"ref": ["a.mother"],
"rows": 1,
"filtered": 100
}
}
}
]
}
}
}
}
}
}
drop table folks;
#
# MDEV-10372: [bb-10.2-mdev9864 tree] EXPLAIN with recursive CTE enters endless recursion
#
create table t1(a int);
insert into t1 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
explain format=json
with recursive T as (select a from t1 union select a+10 from T where a < 1000)
select * from T;
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"table_name": "<derived2>",
"access_type": "ALL",
"rows": 10,
"filtered": 100,
"materialized": {
"query_block": {
"recursive_union": {
"table_name": "<union2,3>",
"access_type": "ALL",
"query_specifications": [
{
"query_block": {
"select_id": 2,
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows": 10,
"filtered": 100
}
}
},
{
"query_block": {
"select_id": 3,
"table": {
"table_name": "<derived2>",
"access_type": "ALL",
"rows": 10,
"filtered": 100,
"attached_condition": "(T.a < 1000)"
}
}
}
]
}
}
}
}
}
}
drop table t1;

101
mysql-test/t/cte_recursive.test
View File

@ -977,5 +977,106 @@ as
select * from ancestors;
--echo #
--echo # EXPLAIN FORMAT=JSON on a query where one recursive CTE uses another:
--echo #
explain
with recursive
prev_gen
as
(
select folks.*
from folks, prev_gen
where folks.id=prev_gen.father or folks.id=prev_gen.mother
union
select *
from folks
where name='Me'
),
ancestors
as
(
select *
from folks
where name='Me'
union
select *
from ancestors
union
select *
from prev_gen
)
select ancestors.name, ancestors.dob from ancestors;
explain FORMAT=JSON
with recursive
prev_gen
as
(
select folks.*
from folks, prev_gen
where folks.id=prev_gen.father or folks.id=prev_gen.mother
union
select *
from folks
where name='Me'
),
ancestors
as
(
select *
from folks
where name='Me2'
union
select *
from ancestors where id < 234
union
select *
from prev_gen where id < 345
)
select ancestors.name, ancestors.dob from ancestors;
--echo #
explain format=json
with recursive
ancestor_couples(h_id, h_name, h_dob, h_father, h_mother,
w_id, w_name, w_dob, w_father, w_mother)
as
(
select h.*, w.*
from folks h, folks w, coupled_ancestors a
where a.father = h.id AND a.mother = w.id
union
select h.*, w.*
from folks v, folks h, folks w
where v.name = 'Me' and
(v.father = h.id AND v.mother= w.id)
),
coupled_ancestors (id, name, dob, father, mother)
as
(
select h_id, h_name, h_dob, h_father, h_mother
from ancestor_couples
union all
select w_id, w_name, w_dob, w_father, w_mother
from ancestor_couples
)
select h_name, h_dob, w_name, w_dob
from ancestor_couples;
drop table folks;
--echo #
--echo # MDEV-10372: [bb-10.2-mdev9864 tree] EXPLAIN with recursive CTE enters endless recursion
--echo #
create table t1(a int);
insert into t1 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
explain format=json
with recursive T as (select a from t1 union select a+10 from T where a < 1000)
select * from T;
drop table t1;

7
sql/sql_explain.cc
View File

@ -547,7 +547,12 @@ void Explain_union::print_explain_json(Explain_query *query,
bool started_object= print_explain_json_cache(writer, is_analyze);
writer->add_member("query_block").start_object();
writer->add_member("union_result").start_object();
if (is_recursive_cte)
writer->add_member("recursive_union").start_object();
else
writer->add_member("union_result").start_object();
// using_temporary_table
make_union_table_name(table_name_buffer);
writer->add_member("table_name").add_str(table_name_buffer);

2
sql/sql_explain.h
View File

@ -327,6 +327,7 @@ class Explain_union : public Explain_node
public:
Explain_union(MEM_ROOT *root, bool is_analyze) :
Explain_node(root),
is_recursive_cte(false),
fake_select_lex_explain(root, is_analyze)
{}
@ -362,6 +363,7 @@ public:
const char *fake_select_type;
bool using_filesort;
bool using_tmp;
bool is_recursive_cte;
/*
Explain data structure for "fake_select_lex" (i.e. for the degenerate

25
sql/sql_lex.cc
View File

@ -4368,7 +4368,26 @@ void st_select_lex::set_explain_type(bool on_the_fly)
type= is_uncacheable ? "UNCACHEABLE UNION": "UNION";
if (this == master_unit()->fake_select_lex)
type= "UNION RESULT";
/*
join below may be =NULL when this functions is called at an early
stage. It will be later called again and we will set the correct
value.
*/
if (join)
{
bool uses_cte= false;
for (JOIN_TAB *tab= first_explain_order_tab(join); tab;
tab= next_explain_order_tab(join, tab))
{
if (tab->table->pos_in_table_list->with)
{
uses_cte= true;
break;
}
}
if (uses_cte)
type= "RECURSIVE UNION";
}
}
}
}
@ -4683,7 +4702,9 @@ int st_select_lex_unit::save_union_explain(Explain_query *output)
new (output->mem_root) Explain_union(output->mem_root,
thd->lex->analyze_stmt);
if (with_element && with_element->is_recursive)
eu->is_recursive_cte= true;
if (derived)
eu->connection_type= Explain_node::EXPLAIN_NODE_DERIVED;
/*

3
sql/sql_select.cc
View File

@ -24186,7 +24186,8 @@ void JOIN_TAB::save_explain_data(Explain_table_access *eta,
In case this is a derived table, here we remember the number of
subselect that used to produce it.
*/
eta->derived_select_number= table->derived_select_number;
if (!(table_list && table_list->is_with_table_recursive_reference()))
eta->derived_select_number= table->derived_select_number;
/* The same for non-merged semi-joins */
eta->non_merged_sjm_number = get_non_merged_semijoin_select();

4
sql/sql_select.h
View File

@ -2278,4 +2278,8 @@ public:
bool test_if_order_compatible(SQL_I_List<ORDER> &a, SQL_I_List<ORDER> &b);
int test_if_group_changed(List<Cached_item> &list);
int create_sort_index(THD *thd, JOIN *join, JOIN_TAB *tab, Filesort *fsort);
JOIN_TAB *first_explain_order_tab(JOIN* join);
JOIN_TAB *next_explain_order_tab(JOIN* join, JOIN_TAB* tab);
#endif /* SQL_SELECT_INCLUDED */

2
sql/sql_union.cc
View File

@ -1166,7 +1166,7 @@ err:
}
// One step of recursive execution
bool st_select_lex_unit::exec_recursive(bool is_driving_recursive)
{
st_select_lex *lex_select_save= thd->lex->current_select;