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Optimisation if simple IN subselect with primary index

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(SCRUM) (part of WL#818)
This commit is contained in:
bell@sanja.is.com.ua 2003-07-07 18:40:19 +03:00
parent 7ad5331768
commit 6348e63f62
7 changed files with 177 additions and 10 deletions
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10
mysql-test/r/subselect.result
View File

@ -1226,7 +1226,15 @@ a
explain select * from t2 where t2.a in (select a from t1);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t2 index NULL PRIMARY 4 NULL 4 Using where; Using index
2 DEPENDENT SUBQUERY t1 eq_ref PRIMARY PRIMARY 4 func 1 Using where; Using index
2 DEPENDENT SUBQUERY t1 simple_in PRIMARY PRIMARY 4 func 1 Using index
select * from t2 where t2.a in (select a from t1 where t1.b <> 30);
a
2
4
explain select * from t2 where t2.a in (select a from t1 where t1.b <> 30);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t2 index NULL PRIMARY 4 NULL 4 Using where; Using index
2 DEPENDENT SUBQUERY t1 simple_in PRIMARY PRIMARY 4 func 1 Using index; Using where
select * from t2 where t2.a in (select t1.a from t1,t3 where t1.b=t3.a);
a
2

2
mysql-test/t/subselect.test
View File

@ -819,6 +819,8 @@ insert into t2 values (2), (3), (4), (5);
insert into t3 values (10,3), (20,4), (30,5);
select * from t2 where t2.a in (select a from t1);
explain select * from t2 where t2.a in (select a from t1);
select * from t2 where t2.a in (select a from t1 where t1.b <> 30);
explain select * from t2 where t2.a in (select a from t1 where t1.b <> 30);
select * from t2 where t2.a in (select t1.a from t1,t3 where t1.b=t3.a);
explain select * from t2 where t2.a in (select t1.a from t1,t3 where t1.b=t3.a);
drop table t1, t2, t3;

82
sql/item_subselect.cc
View File

@ -36,7 +36,7 @@ inline Item * and_items(Item* cond, Item *item)
Item_subselect::Item_subselect():
Item_result_field(), engine_owner(1), value_assigned(0), substitution(0),
have_to_be_excluded(0)
have_to_be_excluded(0), engine_changed(0)
{
reset();
/*
@ -117,16 +117,22 @@ bool Item_subselect::fix_fields(THD *thd_param, TABLE_LIST *tables, Item **ref)
bool Item_subselect::exec()
{
int res;
MEM_ROOT *old_root= my_pthread_getspecific_ptr(MEM_ROOT*, THR_MALLOC);
if (&thd->mem_root != old_root)
{
my_pthread_setspecific_ptr(THR_MALLOC, &thd->mem_root);
int res= engine->exec();
res= engine->exec();
my_pthread_setspecific_ptr(THR_MALLOC, old_root);
return (res);
}
else
return engine->exec();
res= engine->exec();
if (engine_changed)
{
engine_changed= 0;
return exec();
}
return (res);
}
Item::Type Item_subselect::type() const
@ -795,6 +801,13 @@ int subselect_union_engine::prepare()
return unit->prepare(thd, result, 0);
}
int subselect_simplein_engine::prepare()
{
//this never should be called
DBUG_ASSERT(0);
return 1;
}
static Item_result set_row(SELECT_LEX *select_lex, Item * item,
Item_cache **row, bool *maybe_null)
{
@ -873,6 +886,12 @@ void subselect_union_engine::fix_length_and_dec(Item_cache **row)
}
}
void subselect_simplein_engine::fix_length_and_dec(Item_cache **row)
{
//this never should be called
DBUG_ASSERT(0);
}
int subselect_single_select_engine::exec()
{
DBUG_ENTER("subselect_single_select_engine::exec");
@ -889,6 +908,10 @@ int subselect_single_select_engine::exec()
join->thd->lex.current_select= save_select;
DBUG_RETURN(join->error?join->error:1);
}
if (item->engine_changed)
{
DBUG_RETURN(1);
}
}
if ((select_lex->dependent || select_lex->uncacheable) && executed)
{
@ -922,6 +945,51 @@ int subselect_union_engine::exec()
return res;
}
int subselect_simplein_engine::exec()
{
DBUG_ENTER("subselect_simplein_engine::exec");
int error;
TABLE *table= tab->table;
if ((tab->ref.key_err= (*tab->ref.key_copy)->copy()))
{
table->status= STATUS_NOT_FOUND;
error= -1;
}
else
{
error= table->file->index_read(table->record[0],
tab->ref.key_buff,
tab->ref.key_length,HA_READ_KEY_EXACT);
if (error && error != HA_ERR_KEY_NOT_FOUND)
error= report_error(table, error);
else
{
error= 0;
table->null_row= 0;
if (table->status)
((Item_in_subselect *) item)->value= 0;
else
((Item_in_subselect *) item)->value= (!cond || cond->val_int()?1:0);
}
}
{
int tmp= 0;
if ((tmp= table->file->extra(HA_EXTRA_NO_CACHE)))
{
DBUG_PRINT("error", ("extra(HA_EXTRA_NO_CACHE) failed"));
error= 1;
}
if ((tmp= table->file->index_end()))
{
DBUG_PRINT("error", ("index_end() failed"));
error= 1;
}
if (error == 1)
table->file->print_error(tmp, MYF(0));
}
DBUG_RETURN(error != 0)
}
uint subselect_single_select_engine::cols()
{
return select_lex->item_list.elements;
@ -961,3 +1029,9 @@ void subselect_union_engine::exclude()
{
unit->exclude_level();
}
void subselect_simplein_engine::exclude()
{
//this never should be called
DBUG_ASSERT(0);
}

43
sql/item_subselect.h
View File

@ -48,7 +48,12 @@ protected:
bool have_to_be_excluded;
public:
/* changed engine indicator */
bool engine_changed;
enum trans_res {OK, REDUCE, ERROR};
enum subs_type {UNKNOWN_SUBS, SINGLEROW_SUBS,
EXISTS_SUBS, IN_SUBS, ALLANY_SUBS};
Item_subselect();
Item_subselect(Item_subselect *item)
@ -59,9 +64,12 @@ public:
max_columns= item->max_columns;
engine= item->engine;
engine_owner= 0;
engine_changed= item->engine_changed;
name= item->name;
}
virtual subs_type substype() { return UNKNOWN_SUBS; }
/*
We need this method, because some compilers do not allow 'this'
pointer in constructor initialization list, but we need pass pointer
@ -95,6 +103,12 @@ public:
else
str->append("-subselect-");
}
bool change_engine(subselect_engine *eng)
{
engine= eng;
engine_changed= 1;
return eng == 0;
}
friend class select_subselect;
friend class Item_in_optimizer;
@ -116,6 +130,9 @@ public:
max_length= item->max_length;
decimals= item->decimals;
}
subs_type substype() { return SINGLEROW_SUBS; }
void reset();
trans_res select_transformer(JOIN *join);
void store(uint i, Item* item);
@ -152,6 +169,7 @@ public:
}
Item_exists_subselect(): Item_subselect() {}
subs_type substype() { return EXISTS_SUBS; }
void reset()
{
value= 0;
@ -165,6 +183,7 @@ public:
void fix_length_and_dec();
friend class select_exists_subselect;
friend class subselect_simplein_engine;
};
/* IN subselect */
@ -185,6 +204,8 @@ public:
Item_in_subselect(THD *thd, Item * left_expr, st_select_lex *select_lex);
Item_in_subselect(Item_in_subselect *item);
Item_in_subselect(): Item_exists_subselect(), abort_on_null(0) {}
subs_type substype() { return IN_SUBS; }
void reset()
{
value= 0;
@ -218,6 +239,7 @@ public:
Item_allany_subselect(THD *thd, Item * left_expr, compare_func_creator f,
st_select_lex *select_lex);
Item_allany_subselect(Item_allany_subselect *item);
subs_type substype() { return ALLANY_SUBS; }
trans_res select_transformer(JOIN *join);
};
@ -288,3 +310,24 @@ public:
bool uncacheable();
void exclude();
};
struct st_join_table;
class subselect_simplein_engine: public subselect_engine
{
st_join_table *tab;
Item *cond;
public:
subselect_simplein_engine(THD *thd, st_join_table *tab_arg,
Item_subselect *subs, Item *where)
:subselect_engine(thd, subs, 0), tab(tab_arg), cond(where)
{}
int prepare();
void fix_length_and_dec(Item_cache** row);
int exec();
uint cols() { return 1; }
bool dependent() { return 1; }
bool uncacheable() { return 1; }
void exclude();
};

2
sql/sql_lex.h
View File

@ -283,7 +283,7 @@ public:
st_select_lex *return_to;
/* LIMIT clause runtime counters */
ha_rows select_limit_cnt, offset_limit_cnt;
/* not NULL if union used in subselect, point to subselect item */
/* not NULL if unit used in subselect, point to subselect item */
Item_subselect *item;
/* thread handler */
THD *thd;

43
sql/sql_select.cc
View File

@ -32,7 +32,7 @@
const char *join_type_str[]={ "UNKNOWN","system","const","eq_ref","ref",
"MAYBE_REF","ALL","range","index","fulltext",
"ref_or_null"
"ref_or_null","simple_in"
};
static void optimize_keyuse(JOIN *join, DYNAMIC_ARRAY *keyuse_array);
@ -723,6 +723,45 @@ JOIN::optimize()
(select_lex->ftfunc_list->elements ?
SELECT_NO_JOIN_CACHE : 0));
/*
is this simple IN subquery?
*/
if (!group_list && !order && !having &&
unit->item && unit->item->substype() == Item_subselect::IN_SUBS &&
tables == 1 && join_tab[0].type == JT_EQ_REF &&
conds &&
!unit->first_select()->next_select())
{
Item *where= 0;
bool ok= 0;
if (conds->type() == Item::FUNC_ITEM &&
((class Item_func *)this->conds)->functype() == Item_func::EQ_FUNC &&
((Item_func *)conds)->arguments()[0]->type() == Item::REF_ITEM &&
((Item_func *)conds)->arguments()[1]->type() == Item::FIELD_ITEM)
{
ok= 1;
join_tab->info= "Using index";
}
else if (conds->type() == Item::COND_ITEM &&
((class Item_func *)this->conds)->functype() ==
Item_func::COND_AND_FUNC)
{
ok= 1;
where= conds;
join_tab->info= "Using index; Using where";
}
if (ok)
{
join_tab[0].type= JT_SIMPLE_IN;
error= 0;
DBUG_RETURN(unit->item->
change_engine(new subselect_simplein_engine(thd, join_tab,
unit->item,
where)));
}
}
/*
Need to tell Innobase that to play it safe, it should fetch all
columns of the tables: this is because MySQL may build row
@ -5337,7 +5376,7 @@ flush_cached_records(JOIN *join,JOIN_TAB *join_tab,bool skipp_last)
/* Help function when we get some an error from the table handler */
static int report_error(TABLE *table, int error)
int report_error(TABLE *table, int error)
{
if (error == HA_ERR_END_OF_FILE || error == HA_ERR_KEY_NOT_FOUND)
{

5
sql/sql_select.h
View File

@ -75,7 +75,8 @@ typedef struct st_join_cache {
*/
enum join_type { JT_UNKNOWN,JT_SYSTEM,JT_CONST,JT_EQ_REF,JT_REF,JT_MAYBE_REF,
JT_ALL, JT_RANGE, JT_NEXT, JT_FT, JT_REF_OR_NULL};
JT_ALL, JT_RANGE, JT_NEXT, JT_FT, JT_REF_OR_NULL,
JT_SIMPLE_IN};
class JOIN;
@ -305,7 +306,6 @@ bool create_myisam_from_heap(THD *thd, TABLE *table, TMP_TABLE_PARAM *param,
/* functions from opt_sum.cc */
int opt_sum_query(TABLE_LIST *tables, List<Item> &all_fields,COND *conds);
/* class to copying an field/item to a key struct */
class store_key :public Sql_alloc
@ -407,3 +407,4 @@ public:
bool cp_buffer_from_ref(TABLE_REF *ref);
bool error_if_full_join(JOIN *join);
void relink_tables(SELECT_LEX *select_lex);
int report_error(TABLE *table, int error);