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Merge ibabaev@bk-internal.mysql.com:/home/bk/mysql-5.0-opt

Browse source 
into  rurik.mysql.com:/home/igor/mysql-5.0-opt


sql/sql_select.cc:
  Auto merged
This commit is contained in:
unknown 2006-10-17 12:25:53 -07:00
commit e2698fa753
7 changed files with 238 additions and 35 deletions
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49
mysql-test/r/select.result
View file

@ -3562,3 +3562,52 @@ id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 const PRIMARY PRIMARY 4 const 1
1 SIMPLE t2 const b b 22 const 1 Using index
DROP TABLE t1,t2;
CREATE TABLE t1(id int PRIMARY KEY, b int, e int);
CREATE TABLE t2(i int, a int, INDEX si(i), INDEX ai(a));
CREATE TABLE t3(a int PRIMARY KEY, c char(4), INDEX ci(c));
INSERT INTO t1 VALUES
(1,10,19), (2,20,22), (4,41,42), (9,93,95), (7, 77,79),
(6,63,67), (5,55,58), (3,38,39), (8,81,89);
INSERT INTO t2 VALUES
(21,210), (41,410), (82,820), (83,830), (84,840),
(65,650), (51,510), (37,370), (94,940), (76,760),
(22,220), (33,330), (40,400), (95,950), (38,380),
(67,670), (88,880), (57,570), (96,960), (97,970);
INSERT INTO t3 VALUES
(210,'bb'), (950,'ii'), (400,'ab'), (500,'ee'), (220,'gg'),
(440,'gg'), (310,'eg'), (380,'ee'), (840,'bb'), (830,'ff'),
(230,'aa'), (960,'ii'), (410,'aa'), (510,'ee'), (290,'bb'),
(450,'gg'), (320,'dd'), (390,'hh'), (850,'jj'), (860,'ff');
EXPLAIN
SELECT t3.a FROM t1,t2 FORCE INDEX (si),t3
WHERE t1.id = 8 AND t2.i BETWEEN t1.b AND t1.e AND
t3.a=t2.a AND t3.c IN ('bb','ee');
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 const PRIMARY PRIMARY 4 const 1
1 SIMPLE t2 range si si 5 NULL 4 Using where
1 SIMPLE t3 eq_ref PRIMARY,ci PRIMARY 4 test.t2.a 1 Using where
EXPLAIN
SELECT t3.a FROM t1,t2,t3
WHERE t1.id = 8 AND t2.i BETWEEN t1.b AND t1.e AND
t3.a=t2.a AND t3.c IN ('bb','ee') ;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 const PRIMARY PRIMARY 4 const 1
1 SIMPLE t2 range si,ai si 5 NULL 4 Using where
1 SIMPLE t3 eq_ref PRIMARY,ci PRIMARY 4 test.t2.a 1 Using where
EXPLAIN
SELECT t3.a FROM t1,t2 FORCE INDEX (si),t3
WHERE t1.id = 8 AND (t2.i=t1.b OR t2.i=t1.e) AND t3.a=t2.a AND
t3.c IN ('bb','ee');
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 const PRIMARY PRIMARY 4 const 1
1 SIMPLE t2 range si si 5 NULL 2 Using where
1 SIMPLE t3 eq_ref PRIMARY,ci PRIMARY 4 test.t2.a 1 Using where
EXPLAIN
SELECT t3.a FROM t1,t2,t3
WHERE t1.id = 8 AND (t2.i=t1.b OR t2.i=t1.e) AND t3.a=t2.a AND
t3.c IN ('bb','ee');
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 const PRIMARY PRIMARY 4 const 1
1 SIMPLE t2 range si,ai si 5 NULL 2 Using where
1 SIMPLE t3 eq_ref PRIMARY,ci PRIMARY 4 test.t2.a 1 Using where
DROP TABLE t1,t2,t3;

45
mysql-test/t/select.test
View file

@ -3007,6 +3007,8 @@ c7 int, c8 int, c9 int, fulltext key (`c1`));
select distinct match (`c1`) against ('z') , c2, c3, c4,c5, c6,c7, c8
from t1 where c9=1 order by c2, c2;
drop table t1;
#
# Bug #22735: no equality propagation for BETWEEN and IN with STRING arguments
#
@ -3047,3 +3049,46 @@ INSERT INTO t2 VALUES (1,'a'),(2,'b'),(3,'c');
EXPLAIN SELECT t1.a FROM t1 LEFT JOIN t2 ON t2.b=t1.b WHERE t1.a=3;
DROP TABLE t1,t2;
#
# Bug #19579: predicates that become sargable after reading const tables
# are not taken into account by optimizer
#
CREATE TABLE t1(id int PRIMARY KEY, b int, e int);
CREATE TABLE t2(i int, a int, INDEX si(i), INDEX ai(a));
CREATE TABLE t3(a int PRIMARY KEY, c char(4), INDEX ci(c));
INSERT INTO t1 VALUES
(1,10,19), (2,20,22), (4,41,42), (9,93,95), (7, 77,79),
(6,63,67), (5,55,58), (3,38,39), (8,81,89);
INSERT INTO t2 VALUES
(21,210), (41,410), (82,820), (83,830), (84,840),
(65,650), (51,510), (37,370), (94,940), (76,760),
(22,220), (33,330), (40,400), (95,950), (38,380),
(67,670), (88,880), (57,570), (96,960), (97,970);
INSERT INTO t3 VALUES
(210,'bb'), (950,'ii'), (400,'ab'), (500,'ee'), (220,'gg'),
(440,'gg'), (310,'eg'), (380,'ee'), (840,'bb'), (830,'ff'),
(230,'aa'), (960,'ii'), (410,'aa'), (510,'ee'), (290,'bb'),
(450,'gg'), (320,'dd'), (390,'hh'), (850,'jj'), (860,'ff');
EXPLAIN
SELECT t3.a FROM t1,t2 FORCE INDEX (si),t3
WHERE t1.id = 8 AND t2.i BETWEEN t1.b AND t1.e AND
t3.a=t2.a AND t3.c IN ('bb','ee');
EXPLAIN
SELECT t3.a FROM t1,t2,t3
WHERE t1.id = 8 AND t2.i BETWEEN t1.b AND t1.e AND
t3.a=t2.a AND t3.c IN ('bb','ee') ;
EXPLAIN
SELECT t3.a FROM t1,t2 FORCE INDEX (si),t3
WHERE t1.id = 8 AND (t2.i=t1.b OR t2.i=t1.e) AND t3.a=t2.a AND
t3.c IN ('bb','ee');
EXPLAIN
SELECT t3.a FROM t1,t2,t3
WHERE t1.id = 8 AND (t2.i=t1.b OR t2.i=t1.e) AND t3.a=t2.a AND
t3.c IN ('bb','ee');
DROP TABLE t1,t2,t3;

2
sql/item_cmpfunc.cc
View file

@ -1078,6 +1078,8 @@ bool Item_func_between::fix_fields(THD *thd, Item **ref)
if (Item_func_opt_neg::fix_fields(thd, ref))
return 1;
thd->lex->current_select->between_count++;
/* not_null_tables_cache == union(T1(e),T1(e1),T1(e2)) */
if (pred_level && !negated)
return 0;

1
sql/sql_base.cc
View file

@ -4906,6 +4906,7 @@ int setup_conds(THD *thd, TABLE_LIST *tables, TABLE_LIST *leaves,
thd->set_query_id=1;
select_lex->cond_count= 0;
select_lex->between_count= 0;
for (table= tables; table; table= table->next_local)
{

2
sql/sql_lex.cc
View file

@ -1138,7 +1138,7 @@ void st_select_lex::init_query()
initialization is checked for failure.
*/
parent_lex->push_context(&context);
cond_count= with_wild= 0;
cond_count= between_count= with_wild= 0;
conds_processed_with_permanent_arena= 0;
ref_pointer_array= 0;
select_n_having_items= 0;

3
sql/sql_lex.h
View file

@ -530,7 +530,8 @@ public:
list during split_sum_func
*/
uint select_n_having_items;
uint cond_count; /* number of arguments of and/or/xor in where/having */
uint cond_count; /* number of arguments of and/or/xor in where/having/on */
uint between_count; /* number of between predicates in where/having/on */
enum_parsing_place parsing_place; /* where we are parsing expression */
bool with_sum_func; /* sum function indicator */
/*

171
sql/sql_select.cc
View file

@ -35,14 +35,17 @@ const char *join_type_str[]={ "UNKNOWN","system","const","eq_ref","ref",
"index_merge"
};
struct st_sargable_param;
static void optimize_keyuse(JOIN *join, DYNAMIC_ARRAY *keyuse_array);
static bool make_join_statistics(JOIN *join, TABLE_LIST *leaves, COND *conds,
DYNAMIC_ARRAY *keyuse);
static bool update_ref_and_keys(THD *thd, DYNAMIC_ARRAY *keyuse,
JOIN_TAB *join_tab,
JOIN_TAB *join_tab,
uint tables, COND *conds,
COND_EQUAL *cond_equal,
table_map table_map, SELECT_LEX *select_lex);
table_map table_map, SELECT_LEX *select_lex,
st_sargable_param **sargables);
static int sort_keyuse(KEYUSE *a,KEYUSE *b);
static void set_position(JOIN *join,uint index,JOIN_TAB *table,KEYUSE *key);
static bool create_ref_for_key(JOIN *join, JOIN_TAB *j, KEYUSE *org_keyuse,
@ -2044,6 +2047,19 @@ static ha_rows get_quick_record_count(THD *thd, SQL_SELECT *select,
DBUG_RETURN(HA_POS_ERROR); /* This shouldn't happend */
}
/*
This structure is used to collect info on potentially sargable
predicates in order to check whether they become sargable after
reading const tables.
We form a bitmap of indexes that can be used for sargable predicates.
Only such indexes are involved in range analysis.
*/
typedef struct st_sargable_param
{
Field *field; /* field against which to check sargability */
Item **arg_value; /* values of potential keys for lookups */
uint num_values; /* number of values in the above array */
} SARGABLE_PARAM;
/*
Calculate the best possible join and initialize the join structure
@ -2066,6 +2082,7 @@ make_join_statistics(JOIN *join, TABLE_LIST *tables, COND *conds,
JOIN_TAB *stat,*stat_end,*s,**stat_ref;
KEYUSE *keyuse,*start_keyuse;
table_map outer_join=0;
SARGABLE_PARAM *sargables= 0;
JOIN_TAB *stat_vector[MAX_TABLES+1];
DBUG_ENTER("make_join_statistics");
@ -2187,7 +2204,7 @@ make_join_statistics(JOIN *join, TABLE_LIST *tables, COND *conds,
if (conds || outer_join)
if (update_ref_and_keys(join->thd, keyuse_array, stat, join->tables,
conds, join->cond_equal,
~outer_join, join->select_lex))
~outer_join, join->select_lex, &sargables))
DBUG_RETURN(1);
/* Read tables with 0 or 1 rows (system tables) */
@ -2337,6 +2354,26 @@ make_join_statistics(JOIN *join, TABLE_LIST *tables, COND *conds,
}
} while (join->const_table_map & found_ref && ref_changed);
/*
Update info on indexes that can be used for search lookups as
reading const tables may has added new sargable predicates.
*/
if (const_count && sargables)
{
for( ; sargables->field ; sargables++)
{
Field *field= sargables->field;
JOIN_TAB *stat= field->table->reginfo.join_tab;
key_map possible_keys= field->key_start;
possible_keys.intersect(field->table->keys_in_use_for_query);
bool is_const= 1;
for (uint i=0; i< sargables->num_values; i++)
is_const&= sargables->arg_value[i]->const_item();
if (is_const)
stat[0].const_keys.merge(possible_keys);
}
}
/* Calc how many (possible) matched records in each table */
for (s=stat ; s < stat_end ; s++)
@ -2596,6 +2633,7 @@ merge_key_fields(KEY_FIELD *start,KEY_FIELD *new_fields,KEY_FIELD *end,
eq_func True if we used =, <=> or IS NULL
value Value used for comparison with field
usable_tables Tables which can be used for key optimization
sargables IN/OUT Array of found sargable candidates
NOTES
If we are doing a NOT NULL comparison on a NOT NULL field in a outer join
@ -2607,8 +2645,8 @@ merge_key_fields(KEY_FIELD *start,KEY_FIELD *new_fields,KEY_FIELD *end,
static void
add_key_field(KEY_FIELD **key_fields,uint and_level, Item_func *cond,
Field *field, bool eq_func, Item **value, uint num_values,
table_map usable_tables)
Field *field, bool eq_func, Item **value, uint num_values,
table_map usable_tables, SARGABLE_PARAM **sargables)
{
uint exists_optimize= 0;
if (!(field->flags & PART_KEY_FLAG))
@ -2664,6 +2702,19 @@ add_key_field(KEY_FIELD **key_fields,uint and_level, Item_func *cond,
is_const&= value[i]->const_item();
if (is_const)
stat[0].const_keys.merge(possible_keys);
else if (!eq_func)
{
/*
Save info to be able check whether this predicate can be
considered as sargable for range analisis after reading const tables.
We do not save info about equalities as update_const_equal_items
will take care of updating info on keys from sargable equalities.
*/
(*sargables)--;
(*sargables)->field= field;
(*sargables)->arg_value= value;
(*sargables)->num_values= num_values;
}
/*
We can't always use indexes when comparing a string index to a
number. cmp_type() is checked to allow compare of dates to numbers.
@ -2754,6 +2805,7 @@ add_key_field(KEY_FIELD **key_fields,uint and_level, Item_func *cond,
value Value used for comparison with field
Is NULL for BETWEEN and IN
usable_tables Tables which can be used for key optimization
sargables IN/OUT Array of found sargable candidates
NOTES
If field items f1 and f2 belong to the same multiple equality and
@ -2767,11 +2819,12 @@ static void
add_key_equal_fields(KEY_FIELD **key_fields, uint and_level,
Item_func *cond, Item_field *field_item,
bool eq_func, Item **val,
uint num_values, table_map usable_tables)
uint num_values, table_map usable_tables,
SARGABLE_PARAM **sargables)
{
Field *field= field_item->field;
add_key_field(key_fields, and_level, cond, field,
eq_func, val, num_values, usable_tables);
eq_func, val, num_values, usable_tables, sargables);
Item_equal *item_equal= field_item->item_equal;
if (item_equal)
{
@ -2786,7 +2839,8 @@ add_key_equal_fields(KEY_FIELD **key_fields, uint and_level,
if (!field->eq(item->field))
{
add_key_field(key_fields, and_level, cond, item->field,
eq_func, val, num_values, usable_tables);
eq_func, val, num_values, usable_tables,
sargables);
}
}
}
@ -2794,7 +2848,8 @@ add_key_equal_fields(KEY_FIELD **key_fields, uint and_level,
static void
add_key_fields(KEY_FIELD **key_fields,uint *and_level,
COND *cond, table_map usable_tables)
COND *cond, table_map usable_tables,
SARGABLE_PARAM **sargables)
{
if (cond->type() == Item_func::COND_ITEM)
{
@ -2805,20 +2860,20 @@ add_key_fields(KEY_FIELD **key_fields,uint *and_level,
{
Item *item;
while ((item=li++))
add_key_fields(key_fields,and_level,item,usable_tables);
add_key_fields(key_fields,and_level,item,usable_tables,sargables);
for (; org_key_fields != *key_fields ; org_key_fields++)
org_key_fields->level= *and_level;
}
else
{
(*and_level)++;
add_key_fields(key_fields,and_level,li++,usable_tables);
add_key_fields(key_fields,and_level,li++,usable_tables,sargables);
Item *item;
while ((item=li++))
{
KEY_FIELD *start_key_fields= *key_fields;
(*and_level)++;
add_key_fields(key_fields,and_level,item,usable_tables);
add_key_fields(key_fields,and_level,item,usable_tables,sargables);
*key_fields=merge_key_fields(org_key_fields,start_key_fields,
*key_fields,++(*and_level));
}
@ -2849,9 +2904,9 @@ add_key_fields(KEY_FIELD **key_fields,uint *and_level,
cond_func->argument_count() != 2);
add_key_equal_fields(key_fields, *and_level, cond_func,
(Item_field*) (cond_func->key_item()->real_item()),
0, values,
0, values,
cond_func->argument_count()-1,
usable_tables);
usable_tables, sargables);
}
if (cond_func->functype() == Item_func::BETWEEN)
{
@ -2865,7 +2920,8 @@ add_key_fields(KEY_FIELD **key_fields,uint *and_level,
{
field_item= (Item_field *) (cond_func->arguments()[i]->real_item());
add_key_equal_fields(key_fields, *and_level, cond_func,
field_item, 0, values, 1, usable_tables);
field_item, 0, values, 1, usable_tables,
sargables);
}
}
}
@ -2882,7 +2938,8 @@ add_key_fields(KEY_FIELD **key_fields,uint *and_level,
add_key_equal_fields(key_fields, *and_level, cond_func,
(Item_field*) (cond_func->arguments()[0])->real_item(),
equal_func,
cond_func->arguments()+1, 1, usable_tables);
cond_func->arguments()+1, 1, usable_tables,
sargables);
}
if (cond_func->arguments()[1]->real_item()->type() == Item::FIELD_ITEM &&
cond_func->functype() != Item_func::LIKE_FUNC &&
@ -2891,7 +2948,8 @@ add_key_fields(KEY_FIELD **key_fields,uint *and_level,
add_key_equal_fields(key_fields, *and_level, cond_func,
(Item_field*) (cond_func->arguments()[1])->real_item(),
equal_func,
cond_func->arguments(),1,usable_tables);
cond_func->arguments(),1,usable_tables,
sargables);
}
break;
}
@ -2906,7 +2964,7 @@ add_key_fields(KEY_FIELD **key_fields,uint *and_level,
add_key_equal_fields(key_fields, *and_level, cond_func,
(Item_field*) (cond_func->arguments()[0])->real_item(),
cond_func->functype() == Item_func::ISNULL_FUNC,
&tmp, 1, usable_tables);
&tmp, 1, usable_tables, sargables);
}
break;
case Item_func::OPTIMIZE_EQUAL:
@ -2924,7 +2982,7 @@ add_key_fields(KEY_FIELD **key_fields,uint *and_level,
while ((item= it++))
{
add_key_field(key_fields, *and_level, cond_func, item->field,
TRUE, &const_item, 1, usable_tables);
TRUE, &const_item, 1, usable_tables, sargables);
}
}
else
@ -2944,7 +3002,8 @@ add_key_fields(KEY_FIELD **key_fields,uint *and_level,
if (!field->eq(item->field))
{
add_key_field(key_fields, *and_level, cond_func, field,
TRUE, (Item **) &item, 1, usable_tables);
TRUE, (Item **) &item, 1, usable_tables,
sargables);
}
}
it.rewind();
@ -3095,6 +3154,7 @@ sort_keyuse(KEYUSE *a,KEYUSE *b)
nested_join_table IN Nested join pseudo-table to process
end INOUT End of the key field array
and_level INOUT And-level
sargables IN/OUT Array of found sargable candidates
DESCRIPTION
This function populates KEY_FIELD array with entries generated from the
@ -3118,7 +3178,8 @@ sort_keyuse(KEYUSE *a,KEYUSE *b)
*/
static void add_key_fields_for_nj(TABLE_LIST *nested_join_table,
KEY_FIELD **end, uint *and_level)
KEY_FIELD **end, uint *and_level,
SARGABLE_PARAM **sargables)
{
List_iterator<TABLE_LIST> li(nested_join_table->nested_join->join_list);
table_map tables= 0;
@ -3128,12 +3189,12 @@ static void add_key_fields_for_nj(TABLE_LIST *nested_join_table,
while ((table= li++))
{
if (table->nested_join)
add_key_fields_for_nj(table, end, and_level);
add_key_fields_for_nj(table, end, and_level, sargables);
else
if (!table->on_expr)
tables |= table->table->map;
}
add_key_fields(end, and_level, nested_join_table->on_expr, tables);
add_key_fields(end, and_level, nested_join_table->on_expr, tables, sargables);
}
@ -3148,9 +3209,10 @@ static void add_key_fields_for_nj(TABLE_LIST *nested_join_table,
tables Number of tables in join
cond WHERE condition (note that the function analyzes
join_tab[i]->on_expr too)
normal_tables tables not inner w.r.t some outer join (ones for which
normal_tables Tables not inner w.r.t some outer join (ones for which
we can make ref access based the WHERE clause)
select_lex current SELECT
sargables OUT Array of found sargable candidates
RETURN
0 - OK
@ -3159,27 +3221,55 @@ static void add_key_fields_for_nj(TABLE_LIST *nested_join_table,
static bool
update_ref_and_keys(THD *thd, DYNAMIC_ARRAY *keyuse,JOIN_TAB *join_tab,
uint tables, COND *cond, COND_EQUAL *cond_equal,
table_map normal_tables, SELECT_LEX *select_lex)
uint tables, COND *cond, COND_EQUAL *cond_equal,
table_map normal_tables, SELECT_LEX *select_lex,
SARGABLE_PARAM **sargables)
{
uint and_level,i,found_eq_constant;
KEY_FIELD *key_fields, *end, *field;
uint sz;
uint m= 1;
if (cond_equal && cond_equal->max_members)
m= cond_equal->max_members;
if (!(key_fields=(KEY_FIELD*)
thd->alloc(sizeof(key_fields[0])*
(thd->lex->current_select->cond_count+1)*2*m)))
/*
We use the same piece of memory to store both KEY_FIELD
and SARGABLE_PARAM structure.
KEY_FIELD values are placed at the beginning this memory
while SARGABLE_PARAM values are put at the end.
All predicates that are used to fill arrays of KEY_FIELD
and SARGABLE_PARAM structures have at most 2 arguments
except BETWEEN predicates that have 3 arguments and
IN predicates.
This any predicate if it's not BETWEEN/IN can be used
directly to fill at most 2 array elements, either of KEY_FIELD
or SARGABLE_PARAM type. For a BETWEEN predicate 3 elements
can be filled as this predicate is considered as
saragable with respect to each of its argument.
An IN predicate can require at most 1 element as currently
it is considered as sargable only for its first argument.
Multiple equality can add elements that are filled after
substitution of field arguments by equal fields. There
can be not more than cond_equal->max_members such substitutions.
*/
sz= max(sizeof(KEY_FIELD),sizeof(SARGABLE_PARAM))*
(((thd->lex->current_select->cond_count+1)*2 +
thd->lex->current_select->between_count)*m+1);
if (!(key_fields=(KEY_FIELD*) thd->alloc(sz)))
return TRUE; /* purecov: inspected */
and_level= 0;
field= end= key_fields;
*sargables= (SARGABLE_PARAM *) key_fields +
(sz - sizeof((*sargables)[0].field))/sizeof(SARGABLE_PARAM);
/* set a barrier for the array of SARGABLE_PARAM */
(*sargables)[0].field= 0;
if (my_init_dynamic_array(keyuse,sizeof(KEYUSE),20,64))
return TRUE;
if (cond)
{
add_key_fields(&end,&and_level,cond,normal_tables);
add_key_fields(&end,&and_level,cond,normal_tables,sargables);
for (; field != end ; field++)
{
add_key_part(keyuse,field);
@ -3202,7 +3292,7 @@ update_ref_and_keys(THD *thd, DYNAMIC_ARRAY *keyuse,JOIN_TAB *join_tab,
*/
if (*join_tab[i].on_expr_ref)
add_key_fields(&end,&and_level,*join_tab[i].on_expr_ref,
join_tab[i].table->map);
join_tab[i].table->map,sargables);
}
/* Process ON conditions for the nested joins */
@ -3212,7 +3302,7 @@ update_ref_and_keys(THD *thd, DYNAMIC_ARRAY *keyuse,JOIN_TAB *join_tab,
while ((table= li++))
{
if (table->nested_join)
add_key_fields_for_nj(table, &end, &and_level);
add_key_fields_for_nj(table, &end, &and_level, sargables);
}
}
@ -7355,7 +7445,22 @@ static void update_const_equal_items(COND *cond, JOIN_TAB *tab)
((Item_cond*) cond)->functype() == Item_func::MULT_EQUAL_FUNC)
{
Item_equal *item_equal= (Item_equal *) cond;
bool contained_const= item_equal->get_const() != NULL;
item_equal->update_const();
if (!contained_const && item_equal->get_const())
{
/* Update keys for range analysis */
Item_equal_iterator it(*item_equal);
Item_field *item_field;
while ((item_field= it++))
{
Field *field= item_field->field;
JOIN_TAB *stat= field->table->reginfo.join_tab;
key_map possible_keys= field->key_start;
possible_keys.intersect(field->table->keys_in_use_for_query);
stat[0].const_keys.merge(possible_keys);
}
}
}
}