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EXPLAIN FORMAT=JSON: support SJ-Materialization

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- Switch Explain data structure from "flat" representation of
  SJ-Materialization into nested one.
- Update functions that print tabular output to operate on the
  nested structure.
- Add function to generate JSON output.
This commit is contained in:
Sergei Petrunia 2014-12-01 21:35:31 +03:00
parent c46eadb2b3
commit 753718c201
6 changed files with 253 additions and 83 deletions
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6
mysql-test/r/analyze_format_json.result
View file

@ -167,11 +167,5 @@ EXPLAIN
}
}
}
select count(*) from t1 A, t1 B where A.b<20 and B.b<60;
count(*)
1200
select count(*) from t1 A, t1 B where A.b<20 and B.b<60 and A.c > B.c;
count(*)
190
drop table t1;
drop table t0;

54
mysql-test/r/explain_json.result
View file

@ -540,5 +540,57 @@ EXPLAIN
}
}
}
drop table t1;
#
# Semi-join Materialization
#
create table t2 like t1;
insert into t2 select * from t1;
explain format=json
select * from t1,t2 where t1.a in ( select a from t0);
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows": 10,
"filtered": 100
},
"table": {
"table_name": "<subquery2>",
"access_type": "eq_ref",
"possible_keys": ["distinct_key"],
"key": "distinct_key",
"key_length": "4",
"used_key_parts": ["a"],
"ref": ["func"],
"rows": 1,
"filtered": 100,
"materialized": {
"unique": 1,
"query_block": {
"select_id": 2,
"table": {
"table_name": "t0",
"access_type": "ALL",
"rows": 10,
"filtered": 100
}
}
}
},
"block-nl-join": {
"table": {
"table_name": "t2",
"access_type": "ALL",
"rows": 10,
"filtered": 100
},
"buffer_type": "flat",
"join_type": "BNL"
}
}
}
drop table t1,t2;
drop table t0;

11
mysql-test/t/explain_json.test
View file

@ -105,6 +105,15 @@ tbl2 where cnt=tbl2.a;
--echo #
explain format=json
select * from t1 where a in (select max(a) from t1 group by b);
drop table t1;
--echo #
--echo # Semi-join Materialization
--echo #
create table t2 like t1;
insert into t2 select * from t1;
explain format=json
select * from t1,t2 where t1.a in ( select a from t0);
drop table t1,t2;
drop table t0;

75
sql/sql_explain.cc
View file

@ -602,7 +602,7 @@ void Explain_select::replace_table(uint idx, Explain_table_access *new_tab)
}
Explain_select::~Explain_select()
Explain_basic_join::~Explain_basic_join()
{
if (join_tabs)
{
@ -663,34 +663,77 @@ int Explain_select::print_explain(Explain_query *query,
using_fs= false;
}
}
for (uint i=0; i< n_join_tabs; i++)
{
Explain_basic_join* nest;
if ((nest= join_tabs[i]->sjm_nest))
nest->print_explain(query, output, explain_flags, is_analyze);
}
}
return print_explain_for_children(query, output, explain_flags, is_analyze);
}
int Explain_basic_join::print_explain(Explain_query *query,
select_result_sink *output,
uint8 explain_flags, bool is_analyze)
{
for (uint i=0; i< n_join_tabs; i++)
{
if (join_tabs[i]->print_explain(output, explain_flags, is_analyze,
select_id,
"MATERIALIZED" /*select_type*/,
FALSE /*using temporary*/,
FALSE /*using filesort*/))
return 1;
}
return 0;
}
void Explain_select::print_explain_json(Explain_query *query,
Json_writer *writer, bool is_analyze)
{
Json_writer_nesting_guard guard(writer);
writer->add_member("query_block").start_object();
writer->add_member("select_id").add_ll(select_id);
if (message)
{
writer->add_member("query_block").start_object();
writer->add_member("select_id").add_ll(select_id);
writer->add_member("table").start_object();
writer->add_member("message").add_str(message);
writer->end_object();
print_explain_json_for_children(query, writer, is_analyze);
writer->end_object();
}
else
{
for (uint i=0; i< n_join_tabs; i++)
{
// psergey-todo: Need to honor SJM nests...
join_tabs[i]->print_explain_json(query, writer, is_analyze);
}
/*
TODO: how does this approach allow to print ORDER BY members?
Explain_basic_join does not have ORDER/GROUP.
A: factor out join tab printing loop into a common func.
*/
Explain_basic_join::print_explain_json(query, writer, is_analyze);
}
}
void Explain_basic_join::print_explain_json(Explain_query *query,
Json_writer *writer,
bool is_analyze)
{
Json_writer_nesting_guard guard(writer);
writer->add_member("query_block").start_object();
writer->add_member("select_id").add_ll(select_id);
for (uint i=0; i< n_join_tabs; i++)
{
join_tabs[i]->print_explain_json(query, writer, is_analyze);
}
print_explain_json_for_children(query, writer, is_analyze);
writer->end_object();
}
@ -837,17 +880,11 @@ int Explain_table_access::print_explain(select_result_sink *output, uint8 explai
List<Item> item_list;
Item *item_null= new Item_null();
if (sjm_nest_select_id)
select_id= sjm_nest_select_id;
/* `id` column */
item_list.push_back(new Item_int((int32) select_id));
/* `select_type` column */
if (sjm_nest_select_id)
push_str(&item_list, "MATERIALIZED");
else
push_str(&item_list, select_type);
push_str(&item_list, select_type);
/* `table` column */
push_string(&item_list, &table_name);
@ -1242,6 +1279,14 @@ void Explain_table_access::print_explain_json(Explain_query *query,
node->print_explain_json(query, writer, is_analyze);
writer->end_object();
}
if (sjm_nest)
{
/* This is a non-merged semi-join table. Print its contents here */
writer->add_member("materialized").start_object();
writer->add_member("unique").add_ll(1);
sjm_nest->print_explain_json(query, writer, is_analyze);
writer->end_object();
}
writer->end_object();
}

86
sql/sql_explain.h
View file

@ -94,7 +94,8 @@ public:
enum explain_node_type
{
EXPLAIN_UNION,
EXPLAIN_SELECT,
EXPLAIN_SELECT,
EXPLAIN_BASIC_JOIN,
EXPLAIN_UPDATE,
EXPLAIN_DELETE,
EXPLAIN_INSERT
@ -144,6 +145,49 @@ public:
class Explain_table_access;
/*
A basic join. This is only used for SJ-Materialization nests.
Basic join doesn't have ORDER/GROUP/DISTINCT operations. It also cannot be
degenerate.
It has its own select_id.
*/
class Explain_basic_join : public Explain_node
{
public:
enum explain_node_type get_type() { return EXPLAIN_BASIC_JOIN; }
Explain_basic_join() : join_tabs(NULL) {}
~Explain_basic_join();
bool add_table(Explain_table_access *tab)
{
if (!join_tabs)
{
join_tabs= (Explain_table_access**) my_malloc(sizeof(Explain_table_access*) *
MAX_TABLES, MYF(0));
n_join_tabs= 0;
}
join_tabs[n_join_tabs++]= tab;
return false;
}
int get_select_id() { return select_id; }
int select_id;
int print_explain(Explain_query *query, select_result_sink *output,
uint8 explain_flags, bool is_analyze);
void print_explain_json(Explain_query *query, Json_writer *writer,
bool is_analyze);
/* A flat array of Explain structs for tables. */
Explain_table_access** join_tabs;
uint n_join_tabs;
};
/*
EXPLAIN structure for a SELECT.
@ -159,30 +203,16 @@ class Explain_table_access;
a way get node's children.
*/
class Explain_select : public Explain_node
class Explain_select : public Explain_basic_join
{
public:
enum explain_node_type get_type() { return EXPLAIN_SELECT; }
Explain_select() :
message(NULL), join_tabs(NULL),
message(NULL),
using_temporary(false), using_filesort(false)
{}
~Explain_select();
bool add_table(Explain_table_access *tab)
{
if (!join_tabs)
{
join_tabs= (Explain_table_access**) my_malloc(sizeof(Explain_table_access*) *
MAX_TABLES, MYF(0));
n_join_tabs= 0;
}
join_tabs[n_join_tabs++]= tab;
return false;
}
/*
This is used to save the results of "late" test_if_skip_sort_order() calls
that are made from JOIN::exec
@ -190,24 +220,14 @@ public:
void replace_table(uint idx, Explain_table_access *new_tab);
public:
int select_id;
const char *select_type;
int get_select_id() { return select_id; }
/*
If message != NULL, this is a degenerate join plan, and all subsequent
members have no info
*/
const char *message;
/*
A flat array of Explain structs for tables. The order is "just like EXPLAIN
would print them".
*/
Explain_table_access** join_tabs;
uint n_join_tabs;
/* Global join attributes. In tabular form, they are printed on the first row */
bool using_temporary;
bool using_filesort;
@ -521,19 +541,15 @@ public:
non_merged_sjm_number(0),
where_cond(NULL),
cache_cond(NULL),
pushed_index_cond(NULL)
pushed_index_cond(NULL),
sjm_nest(NULL)
{}
~Explain_table_access() { delete sjm_nest; }
void push_extra(enum explain_extra_tag extra_tag);
/* Internals */
public:
/*
0 means this tab is not inside SJM nest and should use Explain_select's id
other value means the tab is inside an SJM nest.
*/
int sjm_nest_select_id;
/* id and 'select_type' are cared-of by the parent Explain_select */
StringBuffer<32> table_name;
@ -610,6 +626,8 @@ public:
Item *pushed_index_cond;
Explain_basic_join *sjm_nest;
int print_explain(select_result_sink *output, uint8 explain_flags,
bool is_analyze,
uint select_id, const char *select_type,

104
sql/sql_select.cc
View file

@ -8186,6 +8186,41 @@ JOIN_TAB *next_breadth_first_tab(JOIN *join, enum enum_exec_or_opt tabs_kind,
}
/*
Enumerate JOIN_TABs in "EXPLAIN order". This order
- const tabs are included
- we enumerate "optimization tabs".
-
*/
JOIN_TAB *first_explain_order_tab(JOIN* join)
{
JOIN_TAB* tab;
tab= join->table_access_tabs;
return (tab->bush_children) ? tab->bush_children->start : tab;
}
JOIN_TAB *next_explain_order_tab(JOIN* join, JOIN_TAB* tab)
{
/* If we're inside SJM nest and have reached its end, get out */
if (tab->last_leaf_in_bush)
return tab->bush_root_tab;
/* Move to next tab in the array we're traversing */
tab++;
if (tab == join->table_access_tabs + join->top_join_tab_count)
return NULL; /* Outside SJM nest and reached EOF */
if (tab->bush_children)
return tab->bush_children->start;
return tab;
}
JOIN_TAB *first_top_level_tab(JOIN *join, enum enum_with_const_tables const_tbls)
{
JOIN_TAB *tab= join->join_tab;
@ -23277,16 +23312,7 @@ void JOIN_TAB::save_explain_data(Explain_table_access *eta, table_map prefix_tab
tab->tracker= &eta->tracker;
tab->jbuf_tracker= &eta->jbuf_tracker;
/* id */
if (tab->bush_root_tab)
{
JOIN_TAB *first_sibling= tab->bush_root_tab->bush_children->start;
eta->sjm_nest_select_id= first_sibling->emb_sj_nest->sj_subq_pred->get_identifier();
}
else
eta->sjm_nest_select_id= 0;
/* select_type is kept in Explain_select */
/* id and select_type are kept in Explain_select */
/* table */
if (table->derived_select_number)
@ -23719,12 +23745,22 @@ int JOIN::save_explain_data_intern(Explain_query *output, bool need_tmp_table,
if (select_lex->master_unit()->derived)
xpl_sel->connection_type= Explain_node::EXPLAIN_NODE_DERIVED;
JOIN_TAB* const first_top_tab= first_breadth_first_tab(join, WALK_OPTIMIZATION_TABS);
if (need_tmp_table)
xpl_sel->using_temporary= true;
for (JOIN_TAB *tab= first_breadth_first_tab(join, WALK_OPTIMIZATION_TABS); tab;
tab= next_breadth_first_tab(join, WALK_OPTIMIZATION_TABS, tab))
if (need_order)
xpl_sel->using_filesort= true;
JOIN_TAB* const first_top_tab= first_breadth_first_tab(join, WALK_OPTIMIZATION_TABS);
JOIN_TAB* prev_bush_root_tab= NULL;
Explain_basic_join *cur_parent= xpl_sel;
for (JOIN_TAB *tab= first_explain_order_tab(join); tab;
tab= next_explain_order_tab(join, tab))
//for (JOIN_TAB *tab= first_breadth_first_tab(join, WALK_OPTIMIZATION_TABS); tab;
// tab= next_breadth_first_tab(join, WALK_OPTIMIZATION_TABS, tab))
{
JOIN_TAB *saved_join_tab= NULL;
TABLE *table=tab->table;
@ -23735,6 +23771,7 @@ int JOIN::save_explain_data_intern(Explain_query *output, bool need_tmp_table,
continue;
}
if (join->table_access_tabs == join->join_tab &&
tab == (first_top_tab + join->const_tables) && pre_sort_join_tab)
{
@ -23743,21 +23780,36 @@ int JOIN::save_explain_data_intern(Explain_query *output, bool need_tmp_table,
}
Explain_table_access *eta= new (output->mem_root) Explain_table_access;
xpl_sel->add_table(eta);
if (tab->bush_root_tab != prev_bush_root_tab)
{
if (tab->bush_root_tab)
{
/*
We've entered an SJ-Materialization nest. Create an object for it.
*/
cur_parent= new Explain_basic_join;
JOIN_TAB *first_child= tab->bush_root_tab->bush_children->start;
cur_parent->select_id=
first_child->emb_sj_nest->sj_subq_pred->get_identifier();
}
else
{
/*
We've just left an SJ-Materialization nest. We are at the join tab
that 'embeds the nest'
*/
DBUG_ASSERT(tab->bush_children);
eta->sjm_nest= cur_parent;
cur_parent= xpl_sel;
}
}
prev_bush_root_tab= tab->bush_root_tab;
cur_parent->add_table(eta);
tab->save_explain_data(eta, used_tables, distinct, first_top_tab);
if (need_tmp_table)
{
need_tmp_table=0;
xpl_sel->using_temporary= true;
}
if (need_order)
{
need_order=0;
xpl_sel->using_filesort= true;
}
if (saved_join_tab)
tab= saved_join_tab;