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Fix for BUG#8877: Implementation of

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"Early NULL-values filtering for ref access" (attempt2+post-review fixes)
1. update_ref_and_keys() accumulates info about null-rejecting
predicates in in KEY_FIELD::null_rejecting, add_key_part saves
these to KEYUSE.
2. create_ref_for_key copies them to TABLE_REF.
3. add_not_null_conds adds "x IS NOT NULL" to join_tab->select_cond of
appropiate JOIN_TAB members.

Includes code cleanups: 
* add_key_field() params: s/COND/Item_func/ (as only Item_funcs are
passed to it)
* add_key_fields() params: JOIN_TAB *stat removed (wasn't used)
This commit is contained in:
sergefp@mysql.com 2005-04-05 02:42:23 +04:00
parent 75a4dc9644
commit d0c9b36224
2 changed files with 162 additions and 12 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

164
sql/sql_select.cc
View file

@ -1995,6 +1995,11 @@ typedef struct key_field_t { // Used when finding key fields
uint level;
uint optimize;
bool eq_func;
/*
If true, the condition this struct represents will not be satisfied
when val IS NULL.
*/
bool null_rejecting;
} KEY_FIELD;
/* Values in optimize */
@ -2011,6 +2016,12 @@ typedef struct key_field_t { // Used when finding key fields
that are internally transformed to something like:
SELECT * FROM t1 WHERE t1.key=outer_ref_field or t1.key IS NULL
KEY_FIELD::null_rejecting is processed as follows:
result has null_rejecting=true if it is set for both ORed references.
for example:
(t2.key = t1.field OR t2.key = t1.field) -> null_rejecting=true
(t2.key = t1.field OR t2.key <=> t1.field) -> null_rejecting=false
*/
static KEY_FIELD *
@ -2044,6 +2055,8 @@ merge_key_fields(KEY_FIELD *start,KEY_FIELD *new_fields,KEY_FIELD *end,
KEY_OPTIMIZE_EXISTS) |
((old->optimize | new_fields->optimize) &
KEY_OPTIMIZE_REF_OR_NULL));
old->null_rejecting= old->null_rejecting &&
new_fields->null_rejecting;
}
}
else if (old->eq_func && new_fields->eq_func &&
@ -2055,6 +2068,8 @@ merge_key_fields(KEY_FIELD *start,KEY_FIELD *new_fields,KEY_FIELD *end,
KEY_OPTIMIZE_EXISTS) |
((old->optimize | new_fields->optimize) &
KEY_OPTIMIZE_REF_OR_NULL));
old->null_rejecting= old->null_rejecting &&
new_fields->null_rejecting;
}
else if (old->eq_func && new_fields->eq_func &&
(old->val->is_null() || new_fields->val->is_null()))
@ -2065,6 +2080,8 @@ merge_key_fields(KEY_FIELD *start,KEY_FIELD *new_fields,KEY_FIELD *end,
/* Remember the NOT NULL value */
if (old->val->is_null())
old->val= new_fields->val;
/* The referred expression can be NULL: */
old->null_rejecting= false;
}
else
{
@ -2119,7 +2136,7 @@ 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, COND *cond,
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)
{
@ -2221,12 +2238,29 @@ add_key_field(KEY_FIELD **key_fields,uint and_level, COND *cond,
(*key_fields)->val= *value;
(*key_fields)->level= and_level;
(*key_fields)->optimize= exists_optimize;
/*
If the condition has form "tbl.keypart = othertbl.field" and
othertbl.field can be NULL, there will be no matches if othertbl.field
has NULL value.
*/
(*key_fields)->null_rejecting= (cond->functype() == Item_func::EQ_FUNC) &&
((*value)->type() == Item::FIELD_ITEM) &&
((Item_field*)*value)->field->maybe_null();
(*key_fields)++;
}
/*
SYNOPSIS
add_key_fields()
key_fields Add KEY_FIELD entries to this array (and move the
pointer)
and_level AND-level (a value that is different for every n-way
AND operation)
cond Condition to analyze
usable_tables Value to pass to add_key_field
*/
static void
add_key_fields(JOIN_TAB *stat,KEY_FIELD **key_fields,uint *and_level,
add_key_fields(KEY_FIELD **key_fields,uint *and_level,
COND *cond, table_map usable_tables)
{
if (cond->type() == Item_func::COND_ITEM)
@ -2238,20 +2272,20 @@ add_key_fields(JOIN_TAB *stat,KEY_FIELD **key_fields,uint *and_level,
{
Item *item;
while ((item=li++))
add_key_fields(stat,key_fields,and_level,item,usable_tables);
add_key_fields(key_fields,and_level,item,usable_tables);
for (; org_key_fields != *key_fields ; org_key_fields++)
org_key_fields->level= *and_level;
}
else
{
(*and_level)++;
add_key_fields(stat,key_fields,and_level,li++,usable_tables);
add_key_fields(key_fields,and_level,li++,usable_tables);
Item *item;
while ((item=li++))
{
KEY_FIELD *start_key_fields= *key_fields;
(*and_level)++;
add_key_fields(stat,key_fields,and_level,item,usable_tables);
add_key_fields(key_fields,and_level,item,usable_tables);
*key_fields=merge_key_fields(org_key_fields,start_key_fields,
*key_fields,++(*and_level));
}
@ -2363,6 +2397,7 @@ add_key_part(DYNAMIC_ARRAY *keyuse_array,KEY_FIELD *key_field)
keyuse.keypart_map= (key_part_map) 1 << part;
keyuse.used_tables=key_field->val->used_tables();
keyuse.optimize= key_field->optimize & KEY_OPTIMIZE_REF_OR_NULL;
keyuse.null_rejecting= key_field->null_rejecting;
VOID(insert_dynamic(keyuse_array,(gptr) &keyuse));
}
}
@ -2456,8 +2491,22 @@ sort_keyuse(KEYUSE *a,KEYUSE *b)
/*
Update keyuse array with all possible keys we can use to fetch rows
join_tab is a array in tablenr_order
stat is a reference array in 'prefered' order.
SYNOPSIS
update_ref_and_keys()
thd
keyuse OUT Put here ordered array of KEYUSE structures
join_tab Array in tablenr_order
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
we can make ref access based the WHERE clause)
select_lex current SELECT
RETURN
0 - OK
1 - Out of memory.
*/
static bool
@ -2478,7 +2527,7 @@ update_ref_and_keys(THD *thd, DYNAMIC_ARRAY *keyuse,JOIN_TAB *join_tab,
return TRUE;
if (cond)
{
add_key_fields(join_tab,&end,&and_level,cond,normal_tables);
add_key_fields(&end,&and_level,cond,normal_tables);
for (; field != end ; field++)
{
add_key_part(keyuse,field);
@ -2492,7 +2541,7 @@ update_ref_and_keys(THD *thd, DYNAMIC_ARRAY *keyuse,JOIN_TAB *join_tab,
{
if (join_tab[i].on_expr)
{
add_key_fields(join_tab,&end,&and_level,join_tab[i].on_expr,
add_key_fields(&end,&and_level,join_tab[i].on_expr,
join_tab[i].table->map);
}
}
@ -3232,6 +3281,7 @@ static bool create_ref_for_key(JOIN *join, JOIN_TAB *j, KEYUSE *org_keyuse,
}
j->ref.key_buff2=j->ref.key_buff+ALIGN_SIZE(length);
j->ref.key_err=1;
j->ref.null_rejecting= 0;
keyuse=org_keyuse;
store_key **ref_key= j->ref.key_copy;
@ -3256,6 +3306,8 @@ static bool create_ref_for_key(JOIN *join, JOIN_TAB *j, KEYUSE *org_keyuse,
uint maybe_null= test(keyinfo->key_part[i].null_bit);
j->ref.items[i]=keyuse->val; // Save for cond removal
if (keyuse->null_rejecting)
j->ref.null_rejecting |= 1 << i;
keyuse_uses_no_tables= keyuse_uses_no_tables && !keyuse->used_tables;
if (!keyuse->used_tables &&
!(join->select_options & SELECT_DESCRIBE))
@ -3410,12 +3462,99 @@ make_simple_join(JOIN *join,TABLE *tmp_table)
}
inline void add_cond_and_fix(Item **e1, Item *e2)
{
if (*e1)
{
Item *res;
if ((res= new Item_cond_and(*e1, e2)))
{
*e1= res;
res->quick_fix_field();
}
}
else
*e1= e2;
}
/*
Add to join_tab->select_cond[i] "table.field IS NOT NULL" conditions we've
inferred from ref/eq_ref access performed.
SYNOPSIS
add_not_null_conds()
join Join to process
NOTES
This function is a part of "Early NULL-values filtering for ref access"
optimization.
Example of this optimization:
For query SELECT * FROM t1,t2 WHERE t2.key=t1.field
and plan " any-access(t1), ref(t2.key=t1.field) "
add "t1.field IS NOT NULL" to t1's table condition.
Description of the optimization:
We look through equalities choosen to perform ref/eq_ref access,
pick equalities that have form "tbl.part_of_key = othertbl.field"
(where othertbl is a non-const table and othertbl.field may be NULL)
and add them to conditions on correspoding tables (othertbl in this
example).
This optimization doesn't affect the choices that ref, range, or join
optimizer make. This was intentional because this was added after 4.1
was GA.
Implementation overview
1. update_ref_and_keys() accumulates info about null-rejecting
predicates in in KEY_FIELD::null_rejecting
1.1 add_key_part saves these to KEYUSE.
2. create_ref_for_key copies them to TABLE_REF.
3. add_not_null_conds adds "x IS NOT NULL" to join_tab->select_cond of
appropiate JOIN_TAB members.
*/
static void add_not_null_conds(JOIN *join)
{
DBUG_ENTER("add_not_null_conds");
for (uint i=join->const_tables ; i < join->tables ; i++)
{
JOIN_TAB *tab=join->join_tab+i;
if ((tab->type == JT_REF || tab->type == JT_REF_OR_NULL) &&
!tab->table->maybe_null)
{
for (uint keypart= 0; keypart < tab->ref.key_parts; keypart++)
{
if (tab->ref.null_rejecting & (1 << keypart))
{
Item *item= tab->ref.items[keypart];
DBUG_ASSERT(item->type() == Item::FIELD_ITEM);
Item_field *not_null_item= (Item_field*)item;
JOIN_TAB *referred_tab= not_null_item->field->table->reginfo.join_tab;
Item_func_isnotnull *null_rej;
if (!(null_rej= new Item_func_isnotnull(not_null_item)))
DBUG_VOID_RETURN;
null_rej->quick_fix_field();
//psergey-todo: Flatten AND's
DBUG_EXECUTE("where",print_where(null_rej,
referred_tab->table->table_name););
add_cond_and_fix(&referred_tab->select_cond, null_rej);
}
}
}
}
DBUG_VOID_RETURN;
}
static bool
make_join_select(JOIN *join,SQL_SELECT *select,COND *cond)
{
DBUG_ENTER("make_join_select");
if (select)
{
add_not_null_conds(join);
table_map used_tables;
if (join->tables > 1)
cond->update_used_tables(); // Tablenr may have changed
@ -3472,13 +3611,14 @@ make_join_select(JOIN *join,SQL_SELECT *select,COND *cond)
}
if (tmp)
{
DBUG_EXECUTE("where",print_where(tmp,tab->table->table_name););
SQL_SELECT *sel=tab->select=(SQL_SELECT*)
join->thd->memdup((gptr) select, sizeof(SQL_SELECT));
if (!sel)
DBUG_RETURN(1); // End of memory
tab->select_cond=sel->cond=tmp;
add_cond_and_fix(&tab->select_cond, tmp);
sel->cond= tab->select_cond;
sel->head=tab->table;
DBUG_EXECUTE("where",print_where(tmp,tab->table->table_name););
if (tab->quick)
{
/* Use quick key read if it's a constant and it's not used

10
sql/sql_select.h
View file

@ -31,6 +31,11 @@ typedef struct keyuse_t {
uint key, keypart, optimize;
key_part_map keypart_map;
ha_rows ref_table_rows;
/*
If true, the comparison this value was created from will not be
satisfied if val has NULL 'value'.
*/
bool null_rejecting;
} KEYUSE;
class store_key;
@ -45,6 +50,11 @@ typedef struct st_table_ref
byte *key_buff2; // key_buff+key_length
store_key **key_copy; //
Item **items; // val()'s for each keypart
/*
(null_rejecting & (1<<i)) means the condition is '=' and no matching
rows will be produced if items[i] IS NULL (see add_not_null_conds())
*/
key_part_map null_rejecting;
table_map depend_map; // Table depends on these tables.
byte *null_ref_key; // null byte position in the key_buf.
// used for REF_OR_NULL optimization.