#At lp:maria based on revid:psergey@askmonty.org-20090617052739-37i1r8lip0m4ft9r
2718 Sergey Petrunia 2009-06-22
MWL#17: Table elimination
- Make elimination check to be able detect cases like t.primary_key_col1=othertbl.col AND t.primary_key_col2=func(t.primary_key_col1).
These are needed to handle e.g. the case of func() being a correlated subquery that selects the latest value.
- If we've removed a condition with subquery predicate, EXPLAIN [EXTENDED] won't show the subquery anymore
modified:
sql/item.cc
sql/item.h
sql/item_subselect.cc
sql/item_subselect.h
sql/item_sum.cc
sql/sql_lex.cc
sql/sql_lex.h
sql/sql_select.cc
sql/sql_select.h
per-file messages:
sql/item.cc
MWL#17: Table elimination
- Add tem_field::check_column_usage_processor(). it allows to check which key parts a condition depends on.
sql/item.h
MWL#17: Table elimination
- Add tem_field::check_column_usage_processor(). it allows to check which key parts a condition depends on.
sql/item_subselect.cc
MWL#17: Table elimination
- Item_subselect got 'eliminated' attribute. It is used only to determine if the subselect should be printed by EXPLAIN.
- Item_subselect got List<Item> refers_to - a list of item in the current select that are referred to from within the subselect.
- Added Item_*::check_column_usage_processor(). it allows to check which key parts a condition depends on.
- Added a comment about possible problem in Item_subselect::walk
sql/item_subselect.h
MWL#17: Table elimination
- Item_subselect got 'eliminated' attribute. It is used only to determine if the subselect should be printed by EXPLAIN.
- Item_subselect got List<Item> refers_to - a list of item in the current select that are referred to from within the subselect.
- Added Item_*::check_column_usage_processor(). it allows to check which key parts a condition depends on.
sql/item_sum.cc
MWL#17: Table elimination
sql/sql_lex.cc
MWL#17: Table elimination
sql/sql_lex.h
MWL#17: Table elimination
sql/sql_select.cc
MWL#17: Table elimination
- Make elimination check to be able detect cases like t.primary_key_col1=othertbl.col AND t.primary_key_col2=func(t.primary_key_col1).
These are needed to handle e.g. the case of func() being a correlated subquery that selects the latest value.
- If we've removed a condition with subquery predicate, EXPLAIN [EXTENDED] won't show the subquery anymore
sql/sql_select.h
MWL#17: Table elimination
=== modified file 'sql/item.cc'
--- a/sql/item.cc 2009-04-25 10:05:32 +0000
+++ b/sql/item.cc 2009-06-22 11:46:31 +0000
@@ -1915,6 +1915,30 @@ void Item_field::reset_field(Field *f)
name= (char*) f->field_name;
}
+bool Item_field::check_column_usage_processor(uchar *arg)
+{
+ Field_processor_info* info=(Field_processor_info*)arg;
+ if (used_tables() & ~info->allowed_tables)
+ return FALSE;
+
+ if (field->table == info->table)
+ {
+ if (!(field->part_of_key.is_set(info->keyno)))
+ return TRUE;
+
+ KEY *key= &field->table->key_info[info->keyno];
+ for (uint part= 0; part < key->key_parts; part++)
+ {
+ if (field->field_index == key->key_part[part].field->field_index)
+ {
+ info->needed_key_parts |= key_part_map(1) << part;
+ break;
+ }
+ }
+ }
+ return FALSE;
+}
+
const char *Item_ident::full_name() const
{
char *tmp;
@@ -3380,7 +3404,7 @@ static void mark_as_dependent(THD *thd,
/* store pointer on SELECT_LEX from which item is dependent */
if (mark_item)
mark_item->depended_from= last;
- current->mark_as_dependent(last);
+ current->mark_as_dependent(last, resolved_item);
if (thd->lex->describe & DESCRIBE_EXTENDED)
{
char warn_buff[MYSQL_ERRMSG_SIZE];
=== modified file 'sql/item.h'
--- a/sql/item.h 2009-06-09 21:11:33 +0000
+++ b/sql/item.h 2009-06-22 11:46:31 +0000
@@ -888,6 +888,8 @@ public:
virtual bool reset_query_id_processor(uchar *query_id_arg) { return 0; }
virtual bool is_expensive_processor(uchar *arg) { return 0; }
virtual bool register_field_in_read_map(uchar *arg) { return 0; }
+ virtual bool check_column_usage_processor(uchar *arg) { return 0; }
+ virtual bool mark_as_eliminated_processor(uchar *arg) { return 0; }
/*
Check if a partition function is allowed
SYNOPSIS
@@ -1012,6 +1014,14 @@ public:
};
+typedef struct
+{
+ table_map allowed_tables;
+ TABLE *table;
+ uint keyno;
+ uint needed_key_parts;
+} Field_processor_info;
+
class sp_head;
@@ -1477,6 +1487,7 @@ public:
bool find_item_in_field_list_processor(uchar *arg);
bool register_field_in_read_map(uchar *arg);
bool check_partition_func_processor(uchar *int_arg) {return FALSE;}
+ bool check_column_usage_processor(uchar *arg);
void cleanup();
bool result_as_longlong()
{
=== modified file 'sql/item_subselect.cc'
--- a/sql/item_subselect.cc 2009-01-31 21:22:44 +0000
+++ b/sql/item_subselect.cc 2009-06-22 11:46:31 +0000
@@ -39,7 +39,7 @@ inline Item * and_items(Item* cond, Item
Item_subselect::Item_subselect():
Item_result_field(), value_assigned(0), thd(0), substitution(0),
engine(0), old_engine(0), used_tables_cache(0), have_to_be_excluded(0),
- const_item_cache(1), engine_changed(0), changed(0), is_correlated(FALSE)
+ const_item_cache(1), in_fix_fields(0), engine_changed(0), changed(0), is_correlated(FALSE)
{
with_subselect= 1;
reset();
@@ -151,10 +151,14 @@ bool Item_subselect::fix_fields(THD *thd
DBUG_ASSERT(fixed == 0);
engine->set_thd((thd= thd_param));
+ if (!in_fix_fields)
+ refers_to.empty();
+ eliminated= FALSE;
if (check_stack_overrun(thd, STACK_MIN_SIZE, (uchar*)&res))
return TRUE;
-
+
+ in_fix_fields++;
res= engine->prepare();
// all transformation is done (used by prepared statements)
@@ -181,12 +185,14 @@ bool Item_subselect::fix_fields(THD *thd
if (!(*ref)->fixed)
ret= (*ref)->fix_fields(thd, ref);
thd->where= save_where;
+ in_fix_fields--;
return ret;
}
// Is it one field subselect?
if (engine->cols() > max_columns)
{
my_error(ER_OPERAND_COLUMNS, MYF(0), 1);
+ in_fix_fields--;
return TRUE;
}
fix_length_and_dec();
@@ -203,11 +209,30 @@ bool Item_subselect::fix_fields(THD *thd
fixed= 1;
err:
+ in_fix_fields--;
thd->where= save_where;
return res;
}
+bool Item_subselect::check_column_usage_processor(uchar *arg)
+{
+ List_iterator<Item> it(refers_to);
+ Item *item;
+ while ((item= it++))
+ {
+ if (item->walk(&Item::check_column_usage_processor,FALSE, arg))
+ return TRUE;
+ }
+ return FALSE;
+}
+
+bool Item_subselect::mark_as_eliminated_processor(uchar *arg)
+{
+ eliminated= TRUE;
+ return FALSE;
+}
+
bool Item_subselect::walk(Item_processor processor, bool walk_subquery,
uchar *argument)
{
@@ -225,6 +250,7 @@ bool Item_subselect::walk(Item_processor
if (lex->having && (lex->having)->walk(processor, walk_subquery,
argument))
return 1;
+ /* TODO: why doesn't this walk the OUTER JOINs' ON expressions */
while ((item=li++))
{
=== modified file 'sql/item_subselect.h'
--- a/sql/item_subselect.h 2008-02-22 10:30:33 +0000
+++ b/sql/item_subselect.h 2009-06-22 11:46:31 +0000
@@ -52,8 +52,16 @@ protected:
bool have_to_be_excluded;
/* cache of constant state */
bool const_item_cache;
-
+
public:
+ /*
+ References from inside the subquery to the select that this predicate is
+ in. References to parent selects not included.
+ */
+ List<Item> refers_to;
+ int in_fix_fields;
+ bool eliminated;
+
/* changed engine indicator */
bool engine_changed;
/* subquery is transformed */
@@ -126,6 +134,8 @@ public:
virtual void reset_value_registration() {}
enum_parsing_place place() { return parsing_place; }
bool walk(Item_processor processor, bool walk_subquery, uchar *arg);
+ bool mark_as_eliminated_processor(uchar *arg);
+ bool check_column_usage_processor(uchar *arg);
/**
Get the SELECT_LEX structure associated with this Item.
=== modified file 'sql/item_sum.cc'
--- a/sql/item_sum.cc 2009-06-09 21:11:33 +0000
+++ b/sql/item_sum.cc 2009-06-22 11:46:31 +0000
@@ -350,7 +350,7 @@ bool Item_sum::register_sum_func(THD *th
sl= sl->master_unit()->outer_select() )
sl->master_unit()->item->with_sum_func= 1;
}
- thd->lex->current_select->mark_as_dependent(aggr_sel);
+ thd->lex->current_select->mark_as_dependent(aggr_sel, NULL);
return FALSE;
}
=== modified file 'sql/sql_lex.cc'
--- a/sql/sql_lex.cc 2009-04-25 10:05:32 +0000
+++ b/sql/sql_lex.cc 2009-06-22 11:46:31 +0000
@@ -1778,7 +1778,7 @@ void st_select_lex_unit::exclude_tree()
'last' should be reachable from this st_select_lex_node
*/
-void st_select_lex::mark_as_dependent(st_select_lex *last)
+void st_select_lex::mark_as_dependent(st_select_lex *last, Item *dependency)
{
/*
Mark all selects from resolved to 1 before select where was
@@ -1804,6 +1804,8 @@ void st_select_lex::mark_as_dependent(st
}
is_correlated= TRUE;
this->master_unit()->item->is_correlated= TRUE;
+ if (dependency)
+ this->master_unit()->item->refers_to.push_back(dependency);
}
bool st_select_lex_node::set_braces(bool value) { return 1; }
=== modified file 'sql/sql_lex.h'
--- a/sql/sql_lex.h 2009-03-17 20:29:24 +0000
+++ b/sql/sql_lex.h 2009-06-22 11:46:31 +0000
@@ -743,7 +743,7 @@ public:
return master_unit()->return_after_parsing();
}
- void mark_as_dependent(st_select_lex *last);
+ void mark_as_dependent(st_select_lex *last, Item *dependency);
bool set_braces(bool value);
bool inc_in_sum_expr();
=== modified file 'sql/sql_select.cc'
--- a/sql/sql_select.cc 2009-06-17 05:27:39 +0000
+++ b/sql/sql_select.cc 2009-06-22 11:46:31 +0000
@@ -2478,6 +2478,14 @@ static ha_rows get_quick_record_count(TH
}
+typedef struct st_keyuse_w_needed_reg
+{
+ KEYUSE *first;
+ key_part_map second;
+
+} Keyuse_w_needed_reg;
+
+static
bool has_eq_ref_access_candidate(TABLE *table, table_map can_refer_to_these)
{
KEYUSE *keyuse= table->reginfo.join_tab->keyuse;
@@ -2494,24 +2502,85 @@ bool has_eq_ref_access_candidate(TABLE *
{
uint key= keyuse->key;
key_part_map bound_parts=0;
- bool ft_key= test(keyuse->keypart == FT_KEYPART);
-
+ uint n_unusable=0;
+ bool ft_key= test(keyuse->keypart == FT_KEYPART);
+ KEY *keyinfo= table->key_info + key;
+ KEYUSE *key_start = keyuse;
+
do /* For each keypart and each way to read it */
{
- if (!(keyuse->used_tables & ~can_refer_to_these) &&
- !(keyuse->optimize & KEY_OPTIMIZE_REF_OR_NULL))
+ if (keyuse->usable)
{
- bound_parts |= keyuse->keypart_map;
+ if(!(keyuse->used_tables & ~can_refer_to_these) &&
+ !(keyuse->optimize & KEY_OPTIMIZE_REF_OR_NULL))
+ {
+ bound_parts |= keyuse->keypart_map;
+ }
}
+ else
+ n_unusable++;
keyuse++;
- } while (keyuse->table && keyuse->key == key);
+ } while (keyuse->table == table && keyuse->key == key);
+
+ if (ft_key || ((keyinfo->flags & (HA_NOSAME | HA_NULL_PART_KEY))
+ != HA_NOSAME))
+ {
+ continue;
+ }
- KEY *keyinfo= table->key_info + key;
- if (!ft_key &&
- ((keyinfo->flags & (HA_NOSAME | HA_NULL_PART_KEY)) == HA_NOSAME) &&
- bound_parts == PREV_BITS(key_part_map, keyinfo->key_parts))
- {
+ if (bound_parts == PREV_BITS(key_part_map, keyinfo->key_parts))
return TRUE;
+ /*
+ Ok, usable keyuse elements didn't help us. Try making use of
+ unusable KEYUSEs (psergey-todo: sane comments:)
+ */
+ if (n_unusable && bound_parts)
+ {
+ /*
+ Check if unusable KEYUSE elements cause all parts of key to be
+ bound. An unusable keyuse element makes a key part bound when it
+ represents the following:
+
+ keyXpartY=func(bound_columns, preceding_tables)
+
+ .
+ */
+ Keyuse_w_needed_reg *uses;
+ if (!(uses= (Keyuse_w_needed_reg*)my_alloca(sizeof(Keyuse_w_needed_reg)*n_unusable)))
+ return FALSE;
+ uint n_uses=0;
+ for (KEYUSE *k= key_start; k!=keyuse; k++)
+ {
+ if (!k->usable && !(k->used_tables & ~can_refer_to_these))
+ {
+ //Walk k->val and check which key parts it depends on.
+ Field_processor_info fp= {can_refer_to_these, table, k->key, 0};
+ if (!k->val->walk(&Item::check_column_usage_processor, FALSE,
+ (uchar*)&fp))
+ {
+ uses[n_uses].first= k;
+ uses[n_uses].second= fp.needed_key_parts;
+ n_uses++;
+ }
+ }
+ }
+ /* Now compute transitive closure */
+ uint n_bounded;
+ do
+ {
+ n_bounded= 0;
+ for (uint i=0; i< n_uses; i++)
+ {
+ /* needed_parts is covered by what is already bound*/
+ if (!(uses[i].second & ~bound_parts))
+ {
+ bound_parts|= key_part_map(1) << uses[i].first->keypart;
+ n_bounded++;
+ }
+ if (bound_parts == PREV_BITS(key_part_map, keyinfo->key_parts))
+ return TRUE;
+ }
+ } while (n_bounded != 0);
}
}
}
@@ -2657,6 +2726,7 @@ eliminate_tables_for_join_list(JOIN *joi
eliminated += tbl->nested_join->join_list.elements;
//psergey-todo: do we need to do anything about removing the join
//nest?
+ tbl->on_expr->walk(&Item::mark_as_eliminated_processor, FALSE, NULL);
}
else
{
@@ -2673,6 +2743,7 @@ eliminate_tables_for_join_list(JOIN *joi
{
mark_table_as_eliminated(join, tbl->table, const_tbl_count,
const_tables);
+ tbl->on_expr->walk(&Item::mark_as_eliminated_processor, FALSE, NULL);
eliminated += 1;
}
}
@@ -3065,14 +3136,16 @@ make_join_statistics(JOIN *join, TABLE_L
{
start_keyuse=keyuse;
key=keyuse->key;
- s->keys.set_bit(key); // QQ: remove this ?
+ if (keyuse->usable)
+ s->keys.set_bit(key); // QQ: remove this ?
refs=0;
const_ref.clear_all();
eq_part.clear_all();
do
{
- if (keyuse->val->type() != Item::NULL_ITEM && !keyuse->optimize)
+ if (keyuse->usable && keyuse->val->type() != Item::NULL_ITEM &&
+ !keyuse->optimize)
{
if (!((~found_const_table_map) & keyuse->used_tables))
const_ref.set_bit(keyuse->keypart);
@@ -3276,6 +3349,7 @@ typedef struct key_field_t {
*/
bool null_rejecting;
bool *cond_guard; /* See KEYUSE::cond_guard */
+ bool usable;
} KEY_FIELD;
@@ -3284,6 +3358,26 @@ typedef struct key_field_t {
This is called for OR between different levels.
+ That is, the function operates on an array of KEY_FIELD elements which has
+ two parts:
+
+ $LEFT_PART $RIGHT_PART
+ +-----------------------+-----------------------+
+ start new_fields end
+
+ $LEFT_PART and $RIGHT_PART are arrays that have KEY_FIELD elements for two
+ parts of the OR condition. Our task is to produce an array of KEY_FIELD
+ elements that would correspond to "$LEFT_PART OR $RIGHT_PART".
+
+ The rules for combining elements are as follows:
+ (keyfieldA1 AND keyfieldA2 AND ...) OR (keyfieldB1 AND keyfieldB2 AND ...)=
+ AND_ij (keyfieldA_i OR keyfieldB_j)
+
+ We discard all (keyfieldA_i OR keyfieldB_j) that refer to different
+ fields. For those referring to the same field, the logic is as follows:
+
+ t.keycol=
+
To be able to do 'ref_or_null' we merge a comparison of a column
and 'column IS NULL' to one test. This is useful for sub select queries
that are internally transformed to something like:.
@@ -3348,13 +3442,18 @@ merge_key_fields(KEY_FIELD *start,KEY_FI
KEY_OPTIMIZE_REF_OR_NULL));
old->null_rejecting= (old->null_rejecting &&
new_fields->null_rejecting);
+ /*
+ The conditions are the same, hence their usabilities should
+ be, too (TODO: shouldn't that apply to the above
+ null_rejecting and optimize attributes?)
+ */
+ DBUG_ASSERT(old->usable == new_fields->usable);
}
}
else if (old->eq_func && new_fields->eq_func &&
old->val->eq_by_collation(new_fields->val,
old->field->binary(),
old->field->charset()))
-
{
old->level= and_level;
old->optimize= ((old->optimize & new_fields->optimize &
@@ -3363,10 +3462,14 @@ merge_key_fields(KEY_FIELD *start,KEY_FI
KEY_OPTIMIZE_REF_OR_NULL));
old->null_rejecting= (old->null_rejecting &&
new_fields->null_rejecting);
+ // "t.key_col=const" predicates are always usable
+ DBUG_ASSERT(old->usable && new_fields->usable);
}
else if (old->eq_func && new_fields->eq_func &&
- ((old->val->const_item() && old->val->is_null()) ||
- new_fields->val->is_null()))
+ ((new_fields->usable && old->val->const_item() &&
+ old->val->is_null()) ||
+ ((old->usable && new_fields->val->is_null()))))
+ /* TODO ^ why is the above asymmetric, why const_item()? */
{
/* field = expression OR field IS NULL */
old->level= and_level;
@@ -3437,6 +3540,7 @@ add_key_field(KEY_FIELD **key_fields,uin
table_map usable_tables, SARGABLE_PARAM **sargables)
{
uint exists_optimize= 0;
+ bool optimizable=0;
if (!(field->flags & PART_KEY_FLAG))
{
// Don't remove column IS NULL on a LEFT JOIN table
@@ -3449,15 +3553,15 @@ add_key_field(KEY_FIELD **key_fields,uin
else
{
table_map used_tables=0;
- bool optimizable=0;
for (uint i=0; i<num_values; i++)
{
used_tables|=(value[i])->used_tables();
if (!((value[i])->used_tables() & (field->table->map | RAND_TABLE_BIT)))
optimizable=1;
}
- if (!optimizable)
- return;
+ // psergey-tbl-elim:
+ // if (!optimizable)
+ // return;
if (!(usable_tables & field->table->map))
{
if (!eq_func || (*value)->type() != Item::NULL_ITEM ||
@@ -3470,7 +3574,8 @@ add_key_field(KEY_FIELD **key_fields,uin
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].keys.merge(possible_keys); // Add possible keys
+ if (optimizable)
+ stat[0].keys.merge(possible_keys); // Add possible keys
/*
Save the following cases:
@@ -3563,6 +3668,7 @@ add_key_field(KEY_FIELD **key_fields,uin
(*key_fields)->val= *value;
(*key_fields)->level= and_level;
(*key_fields)->optimize= exists_optimize;
+ (*key_fields)->usable= optimizable;
/*
If the condition has form "tbl.keypart = othertbl.field" and
othertbl.field can be NULL, there will be no matches if othertbl.field
@@ -3874,6 +3980,7 @@ add_key_part(DYNAMIC_ARRAY *keyuse_array
keyuse.optimize= key_field->optimize & KEY_OPTIMIZE_REF_OR_NULL;
keyuse.null_rejecting= key_field->null_rejecting;
keyuse.cond_guard= key_field->cond_guard;
+ keyuse.usable= key_field->usable;
VOID(insert_dynamic(keyuse_array,(uchar*) &keyuse));
}
}
@@ -3954,6 +4061,11 @@ sort_keyuse(KEYUSE *a,KEYUSE *b)
return (int) (a->key - b->key);
if (a->keypart != b->keypart)
return (int) (a->keypart - b->keypart);
+
+ // Usable ones go before the unusable
+ if (a->usable != b->usable)
+ return (int)a->usable - (int)b->usable;
+
// Place const values before other ones
if ((res= test((a->used_tables & ~OUTER_REF_TABLE_BIT)) -
test((b->used_tables & ~OUTER_REF_TABLE_BIT))))
@@ -4164,7 +4276,8 @@ update_ref_and_keys(THD *thd, DYNAMIC_AR
found_eq_constant=0;
for (i=0 ; i < keyuse->elements-1 ; i++,use++)
{
- if (!use->used_tables && use->optimize != KEY_OPTIMIZE_REF_OR_NULL)
+ if (use->usable && !use->used_tables &&
+ use->optimize != KEY_OPTIMIZE_REF_OR_NULL)
use->table->const_key_parts[use->key]|= use->keypart_map;
if (use->keypart != FT_KEYPART)
{
@@ -4188,7 +4301,8 @@ update_ref_and_keys(THD *thd, DYNAMIC_AR
/* Save ptr to first use */
if (!use->table->reginfo.join_tab->keyuse)
use->table->reginfo.join_tab->keyuse=save_pos;
- use->table->reginfo.join_tab->checked_keys.set_bit(use->key);
+ if (use->usable)
+ use->table->reginfo.join_tab->checked_keys.set_bit(use->key);
save_pos++;
}
i=(uint) (save_pos-(KEYUSE*) keyuse->buffer);
@@ -4218,7 +4332,7 @@ static void optimize_keyuse(JOIN *join,
To avoid bad matches, we don't make ref_table_rows less than 100.
*/
keyuse->ref_table_rows= ~(ha_rows) 0; // If no ref
- if (keyuse->used_tables &
+ if (keyuse->usable && keyuse->used_tables &
(map= (keyuse->used_tables & ~join->const_table_map &
~OUTER_REF_TABLE_BIT)))
{
@@ -4411,7 +4525,8 @@ best_access_path(JOIN *join,
if 1. expression doesn't refer to forward tables
2. we won't get two ref-or-null's
*/
- if (!(remaining_tables & keyuse->used_tables) &&
+ if (keyuse->usable &&
+ !(remaining_tables & keyuse->used_tables) &&
!(ref_or_null_part && (keyuse->optimize &
KEY_OPTIMIZE_REF_OR_NULL)))
{
@@ -5915,9 +6030,11 @@ static bool create_ref_for_key(JOIN *joi
uint i;
for (i=0 ; i < keyparts ; keyuse++,i++)
{
- while (keyuse->keypart != i ||
- ((~used_tables) & keyuse->used_tables))
+ while (keyuse->keypart != i || ((~used_tables) & keyuse->used_tables) ||
+ !keyuse->usable)
+ {
keyuse++; /* Skip other parts */
+ }
uint maybe_null= test(keyinfo->key_part[i].null_bit);
j->ref.items[i]=keyuse->val; // Save for cond removal
@@ -16853,8 +16970,11 @@ static void select_describe(JOIN *join,
unit;
unit= unit->next_unit())
{
- if (mysql_explain_union(thd, unit, result))
- DBUG_VOID_RETURN;
+ if (!(unit->item && unit->item->eliminated))
+ {
+ if (mysql_explain_union(thd, unit, result))
+ DBUG_VOID_RETURN;
+ }
}
DBUG_VOID_RETURN;
}
=== modified file 'sql/sql_select.h'
--- a/sql/sql_select.h 2009-06-14 12:35:04 +0000
+++ b/sql/sql_select.h 2009-06-22 11:46:31 +0000
@@ -51,6 +51,7 @@ typedef struct keyuse_t {
NULL - Otherwise (the source equality can't be turned off)
*/
bool *cond_guard;
+ bool usable;
} KEYUSE;
class store_key;
