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WL#3527: Extend IGNORE INDEX so places where index is ignored

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can be specified
Currently MySQL allows one to specify what indexes to ignore during
join optimization. The scope of the current USE/FORCE/IGNORE INDEX 
statement is only the FROM clause, while all other clauses are not 
affected.

However, in certain cases, the optimizer
may incorrectly choose an index for sorting and/or grouping, and
produce an inefficient query plan.

This task provides the means to specify what indexes are
ignored/used for what operation in a more fine-grained manner, thus
making it possible to manually force a better plan. We do this
by extending the current IGNORE/USE/FORCE INDEX syntax to:

IGNORE/USE/FORCE INDEX [FOR {JOIN | ORDER | GROUP BY}]

so that:
- if no FOR is specified, the index hint will apply everywhere.
- if MySQL is started with the compatibility option --old_mode then
  an index hint without a FOR clause works as in 5.0 (i.e, the 
  index will only be ignored for JOINs, but can still be used to
  compute ORDER BY).

See the WL#3527 for further details.
This commit is contained in:
gkodinov/kgeorge@macbook.gmz
2007-03-05 19:08:41 +02:00
parent 6a49f0cd93
commit b9c82eaa89
25 changed files with 727 additions and 458 deletions
Download Patch File Download Diff File Expand all files Collapse all files

96
sql/sql_select.cc
View File

@ -165,13 +165,15 @@ static COND *make_cond_for_table(COND *cond,table_map table,
static Item* part_of_refkey(TABLE *form,Field *field);
uint find_shortest_key(TABLE *table, const key_map *usable_keys);
static bool test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,
ha_rows select_limit, bool no_changes);
ha_rows select_limit, bool no_changes,
key_map *map);
static bool list_contains_unique_index(TABLE *table,
bool (*find_func) (Field *, void *), void *data);
static bool find_field_in_item_list (Field *field, void *data);
static bool find_field_in_order_list (Field *field, void *data);
static int create_sort_index(THD *thd, JOIN *join, ORDER *order,
ha_rows filesort_limit, ha_rows select_limit);
ha_rows filesort_limit, ha_rows select_limit,
bool is_order_by);
static int remove_duplicates(JOIN *join,TABLE *entry,List<Item> &fields,
Item *having);
static int remove_dup_with_compare(THD *thd, TABLE *entry, Field **field,
@ -916,14 +918,15 @@ JOIN::optimize()
JOIN_TAB *tab= &join_tab[const_tables];
bool all_order_fields_used;
if (order)
skip_sort_order= test_if_skip_sort_order(tab, order, select_limit, 1);
skip_sort_order= test_if_skip_sort_order(tab, order, select_limit, 1,
&tab->table->keys_in_use_for_order_by);
if ((group_list=create_distinct_group(thd, select_lex->ref_pointer_array,
order, fields_list,
&all_order_fields_used)))
{
bool skip_group= (skip_sort_order &&
test_if_skip_sort_order(tab, group_list, select_limit,
1) != 0);
test_if_skip_sort_order(tab, group_list, select_limit, 1,
&tab->table->keys_in_use_for_group_by) != 0);
if ((skip_group && all_order_fields_used) ||
select_limit == HA_POS_ERROR ||
(order && !skip_sort_order))
@ -1113,7 +1116,9 @@ JOIN::optimize()
((group_list &&
(!simple_group ||
!test_if_skip_sort_order(&join_tab[const_tables], group_list,
unit->select_limit_cnt, 0))) ||
unit->select_limit_cnt, 0,
&join_tab[const_tables].table->
keys_in_use_for_group_by))) ||
select_distinct) &&
tmp_table_param.quick_group && !procedure)
{
@ -1215,7 +1220,7 @@ JOIN::optimize()
DBUG_PRINT("info",("Sorting for group"));
thd->proc_info="Sorting for group";
if (create_sort_index(thd, this, group_list,
HA_POS_ERROR, HA_POS_ERROR) ||
HA_POS_ERROR, HA_POS_ERROR, FALSE) ||
alloc_group_fields(this, group_list) ||
make_sum_func_list(all_fields, fields_list, 1) ||
setup_sum_funcs(thd, sum_funcs))
@ -1232,7 +1237,7 @@ JOIN::optimize()
DBUG_PRINT("info",("Sorting for order"));
thd->proc_info="Sorting for order";
if (create_sort_index(thd, this, order,
HA_POS_ERROR, HA_POS_ERROR))
HA_POS_ERROR, HA_POS_ERROR, TRUE))
DBUG_RETURN(1);
order=0;
}
@ -1259,7 +1264,9 @@ JOIN::optimize()
{
/* Should always succeed */
if (test_if_skip_sort_order(&join_tab[const_tables],
order, unit->select_limit_cnt, 0))
order, unit->select_limit_cnt, 0,
&join_tab[const_tables].table->
keys_in_use_for_order_by))
order=0;
}
}
@ -1452,7 +1459,9 @@ JOIN::exec()
(const_tables == tables ||
((simple_order || skip_sort_order) &&
test_if_skip_sort_order(&join_tab[const_tables], order,
select_limit, 0))))
select_limit, 0,
&join_tab[const_tables].table->
keys_in_use_for_order_by))))
order=0;
having= tmp_having;
select_describe(this, need_tmp,
@ -1628,7 +1637,7 @@ JOIN::exec()
DBUG_VOID_RETURN;
}
if (create_sort_index(thd, curr_join, curr_join->group_list,
HA_POS_ERROR, HA_POS_ERROR) ||
HA_POS_ERROR, HA_POS_ERROR, FALSE) ||
make_group_fields(this, curr_join))
{
DBUG_VOID_RETURN;
@ -1844,7 +1853,8 @@ JOIN::exec()
curr_join->group_list : curr_join->order,
curr_join->select_limit,
(select_options & OPTION_FOUND_ROWS ?
HA_POS_ERROR : unit->select_limit_cnt)))
HA_POS_ERROR : unit->select_limit_cnt),
curr_join->group_list ? TRUE : FALSE))
DBUG_VOID_RETURN;
sortorder= curr_join->sortorder;
if (curr_join->const_tables != curr_join->tables &&
@ -3842,7 +3852,7 @@ best_access_path(JOIN *join,
/* Limit the number of matched rows */
tmp= records;
set_if_smaller(tmp, (double) thd->variables.max_seeks_for_key);
if (table->used_keys.is_set(key))
if (table->covering_keys.is_set(key))
{
/* we can use only index tree */
uint keys_per_block= table->file->stats.block_size/2/
@ -4009,7 +4019,7 @@ best_access_path(JOIN *join,
/* Limit the number of matched rows */
set_if_smaller(tmp, (double) thd->variables.max_seeks_for_key);
if (table->used_keys.is_set(key))
if (table->covering_keys.is_set(key))
{
/* we can use only index tree */
uint keys_per_block= table->file->stats.block_size/2/
@ -4068,7 +4078,7 @@ best_access_path(JOIN *join,
!(s->quick && best_key && s->quick->index == best_key->key && // (2)
best_max_key_part >= s->table->quick_key_parts[best_key->key]) &&// (2)
!((s->table->file->ha_table_flags() & HA_TABLE_SCAN_ON_INDEX) && // (3)
! s->table->used_keys.is_clear_all() && best_key) && // (3)
! s->table->covering_keys.is_clear_all() && best_key) && // (3)
!(s->table->force_index && best_key && !s->quick)) // (4)
{ // Check full join
ha_rows rnd_records= s->found_records;
@ -5965,7 +5975,7 @@ make_join_readinfo(JOIN *join, ulonglong options)
(table == join->sort_by_table &&
(!join->order || join->skip_sort_order ||
test_if_skip_sort_order(tab, join->order, join->select_limit,
1))
1, &table->keys_in_use_for_order_by))
) ||
(join->sort_by_table == (TABLE *) 1 && i != join->const_tables))
ordered_set= 1;
@ -5982,7 +5992,7 @@ make_join_readinfo(JOIN *join, ulonglong options)
table->status=STATUS_NO_RECORD;
tab->read_first_record= join_read_const;
tab->read_record.read_record= join_no_more_records;
if (table->used_keys.is_set(tab->ref.key) &&
if (table->covering_keys.is_set(tab->ref.key) &&
!table->no_keyread)
{
table->key_read=1;
@ -6000,7 +6010,7 @@ make_join_readinfo(JOIN *join, ulonglong options)
tab->quick=0;
tab->read_first_record= join_read_key;
tab->read_record.read_record= join_no_more_records;
if (table->used_keys.is_set(tab->ref.key) &&
if (table->covering_keys.is_set(tab->ref.key) &&
!table->no_keyread)
{
table->key_read=1;
@ -6017,7 +6027,7 @@ make_join_readinfo(JOIN *join, ulonglong options)
}
delete tab->quick;
tab->quick=0;
if (table->used_keys.is_set(tab->ref.key) &&
if (table->covering_keys.is_set(tab->ref.key) &&
!table->no_keyread)
{
table->key_read=1;
@ -6103,15 +6113,15 @@ make_join_readinfo(JOIN *join, ulonglong options)
{
if (tab->select && tab->select->quick &&
tab->select->quick->index != MAX_KEY && //not index_merge
table->used_keys.is_set(tab->select->quick->index))
table->covering_keys.is_set(tab->select->quick->index))
{
table->key_read=1;
table->file->extra(HA_EXTRA_KEYREAD);
}
else if (!table->used_keys.is_clear_all() &&
else if (!table->covering_keys.is_clear_all() &&
!(tab->select && tab->select->quick))
{ // Only read index tree
tab->index=find_shortest_key(table, & table->used_keys);
tab->index=find_shortest_key(table, & table->covering_keys);
tab->read_first_record= join_read_first;
tab->type=JT_NEXT; // Read with index_first / index_next
}
@ -9179,7 +9189,7 @@ create_tmp_table(THD *thd,TMP_TABLE_PARAM *param,List<Item> &fields,
table->copy_blobs= 1;
table->in_use= thd;
table->quick_keys.init();
table->used_keys.init();
table->covering_keys.init();
table->keys_in_use_for_query.init();
table->s= share;
@ -10804,7 +10814,7 @@ join_read_const_table(JOIN_TAB *tab, POSITION *pos)
}
else
{
if (!table->key_read && table->used_keys.is_set(tab->ref.key) &&
if (!table->key_read && table->covering_keys.is_set(tab->ref.key) &&
!table->no_keyread &&
(int) table->reginfo.lock_type <= (int) TL_READ_HIGH_PRIORITY)
{
@ -11109,7 +11119,7 @@ join_read_first(JOIN_TAB *tab)
{
int error;
TABLE *table=tab->table;
if (!table->key_read && table->used_keys.is_set(tab->index) &&
if (!table->key_read && table->covering_keys.is_set(tab->index) &&
!table->no_keyread)
{
table->key_read=1;
@ -11148,7 +11158,7 @@ join_read_last(JOIN_TAB *tab)
{
TABLE *table=tab->table;
int error;
if (!table->key_read && table->used_keys.is_set(tab->index) &&
if (!table->key_read && table->covering_keys.is_set(tab->index) &&
!table->no_keyread)
{
table->key_read=1;
@ -12170,7 +12180,7 @@ find_field_in_item_list (Field *field, void *data)
static bool
test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit,
bool no_changes)
bool no_changes, key_map *map)
{
int ref_key;
uint ref_key_parts;
@ -12184,9 +12194,16 @@ test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit,
Check which keys can be used to resolve ORDER BY.
We must not try to use disabled keys.
*/
usable_keys= table->s->keys_in_use;
/* we must not consider keys that are disabled by IGNORE INDEX */
usable_keys.intersect(table->keys_in_use_for_query);
usable_keys= *map;
/*
If there is a covering index, and we have IGNORE INDEX FOR GROUP/ORDER
and this index is used for the JOIN part, then we have to ignore the
IGNORE INDEX FOR GROUP/ORDER
*/
if (table->key_read ||
(table->covering_keys.is_set(tab->index) && !table->no_keyread))
usable_keys.set_bit (tab->index);
for (ORDER *tmp_order=order; tmp_order ; tmp_order=tmp_order->next)
{
@ -12244,8 +12261,8 @@ test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit,
If using index only read, only consider other possible index only
keys
*/
if (table->used_keys.is_set(ref_key))
usable_keys.intersect(table->used_keys);
if (table->covering_keys.is_set(ref_key))
usable_keys.intersect(table->covering_keys);
if ((new_ref_key= test_if_subkey(order, table, ref_key, ref_key_parts,
&usable_keys)) < MAX_KEY)
{
@ -12360,7 +12377,7 @@ test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit,
if (select_limit >= table->file->stats.records)
{
keys= *table->file->keys_to_use_for_scanning();
keys.merge(table->used_keys);
keys.merge(table->covering_keys);
/*
We are adding here also the index specified in FORCE INDEX clause,
@ -12388,7 +12405,7 @@ test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit,
tab->read_first_record= (flag > 0 ? join_read_first:
join_read_last);
tab->type=JT_NEXT; // Read with index_first(), index_next()
if (table->used_keys.is_set(nr))
if (table->covering_keys.is_set(nr))
{
table->key_read=1;
table->file->extra(HA_EXTRA_KEYREAD);
@ -12414,6 +12431,8 @@ test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit,
filesort_limit Max number of rows that needs to be sorted
select_limit Max number of rows in final output
Used to decide if we should use index or not
is_order_by true if we are sorting on ORDER BY, false if GROUP BY
Used to decide if we should use index or not
IMPLEMENTATION
@ -12432,7 +12451,8 @@ test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit,
static int
create_sort_index(THD *thd, JOIN *join, ORDER *order,
ha_rows filesort_limit, ha_rows select_limit)
ha_rows filesort_limit, ha_rows select_limit,
bool is_order_by)
{
uint length;
ha_rows examined_rows;
@ -12453,7 +12473,9 @@ create_sort_index(THD *thd, JOIN *join, ORDER *order,
*/
if ((order != join->group_list ||
!(join->select_options & SELECT_BIG_RESULT)) &&
test_if_skip_sort_order(tab,order,select_limit,0))
test_if_skip_sort_order(tab,order,select_limit,0,
is_order_by ? &table->keys_in_use_for_order_by :
&table->keys_in_use_for_group_by))
DBUG_RETURN(0);
if (!(join->sortorder=
make_unireg_sortorder(order,&length,join->sortorder)))
@ -15047,7 +15069,7 @@ static void select_describe(JOIN *join, bool need_tmp_table, bool need_order,
/* Build "Extra" field and add it to item_list. */
my_bool key_read=table->key_read;
if ((tab->type == JT_NEXT || tab->type == JT_CONST) &&
table->used_keys.is_set(tab->index))
table->covering_keys.is_set(tab->index))
key_read=1;
if (quick_type == QUICK_SELECT_I::QS_TYPE_ROR_INTERSECT &&
!((QUICK_ROR_INTERSECT_SELECT*)tab->select->quick)->need_to_fetch_row)