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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
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37
sql/sql_base.cc
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@ -1792,8 +1792,6 @@ bool reopen_name_locked_table(THD* thd, TABLE_LIST* table_list)
table->const_table=0;
table->null_row= table->maybe_null= table->force_index= 0;
table->status=STATUS_NO_RECORD;
table->keys_in_use_for_query= share->keys_in_use;
table->used_keys= share->keys_for_keyread;
DBUG_RETURN(FALSE);
}
@ -2115,9 +2113,7 @@ TABLE *open_table(THD *thd, TABLE_LIST *table_list, MEM_ROOT *mem_root,
table->const_table=0;
table->null_row= table->maybe_null= table->force_index= 0;
table->status=STATUS_NO_RECORD;
table->keys_in_use_for_query= table->s->keys_in_use;
table->insert_values= 0;
table->used_keys= table->s->keys_for_keyread;
table->fulltext_searched= 0;
table->file->ft_handler= 0;
if (table->timestamp_field)
@ -2202,8 +2198,6 @@ static bool reopen_table(TABLE *table)
tmp.null_row= table->null_row;
tmp.maybe_null= table->maybe_null;
tmp.status= table->status;
tmp.keys_in_use_for_query= tmp.s->keys_in_use;
tmp.used_keys= tmp.s->keys_for_keyread;
tmp.s->table_map_id= table->s->table_map_id;
@ -3621,7 +3615,7 @@ static void update_field_dependencies(THD *thd, Field *field, TABLE *table)
been set for all fields (for example for view).
*/
table->used_keys.intersect(field->part_of_key);
table->covering_keys.intersect(field->part_of_key);
table->merge_keys.merge(field->part_of_key);
if (thd->mark_used_columns == MARK_COLUMNS_READ)
@ -4798,7 +4792,7 @@ mark_common_columns(THD *thd, TABLE_LIST *table_ref_1, TABLE_LIST *table_ref_2,
TABLE *table_1= nj_col_1->table_ref->table;
/* Mark field_1 used for table cache. */
bitmap_set_bit(table_1->read_set, field_1->field_index);
table_1->used_keys.intersect(field_1->part_of_key);
table_1->covering_keys.intersect(field_1->part_of_key);
table_1->merge_keys.merge(field_1->part_of_key);
}
if (field_2)
@ -4806,7 +4800,7 @@ mark_common_columns(THD *thd, TABLE_LIST *table_ref_1, TABLE_LIST *table_ref_2,
TABLE *table_2= nj_col_2->table_ref->table;
/* Mark field_2 used for table cache. */
bitmap_set_bit(table_2->read_set, field_2->field_index);
table_2->used_keys.intersect(field_2->part_of_key);
table_2->covering_keys.intersect(field_2->part_of_key);
table_2->merge_keys.merge(field_2->part_of_key);
}
@ -5446,25 +5440,8 @@ bool setup_tables(THD *thd, Name_resolution_context *context,
tablenr= 0;
}
setup_table_map(table, table_list, tablenr);
table->used_keys= table->s->keys_for_keyread;
table->merge_keys.clear_all();
if (table_list->use_index)
{
key_map map;
get_key_map_from_key_list(&map, table, table_list->use_index);
if (map.is_set_all())
DBUG_RETURN(1);
table->keys_in_use_for_query=map;
}
if (table_list->ignore_index)
{
key_map map;
get_key_map_from_key_list(&map, table, table_list->ignore_index);
if (map.is_set_all())
DBUG_RETURN(1);
table->keys_in_use_for_query.subtract(map);
}
table->used_keys.intersect(table->keys_in_use_for_query);
if (table_list->process_index_hints(table))
DBUG_RETURN(1);
}
if (tablenr > MAX_TABLES)
{
@ -5746,7 +5723,7 @@ insert_fields(THD *thd, Name_resolution_context *context, const char *db_name,
bitmap_set_bit(field->table->read_set, field->field_index);
if (table)
{
table->used_keys.intersect(field->part_of_key);
table->covering_keys.intersect(field->part_of_key);
table->merge_keys.merge(field->part_of_key);
}
if (tables->is_natural_join)
@ -5764,7 +5741,7 @@ insert_fields(THD *thd, Name_resolution_context *context, const char *db_name,
if (field_table)
{
thd->used_tables|= field_table->map;
field_table->used_keys.intersect(field->part_of_key);
field_table->covering_keys.intersect(field->part_of_key);
field_table->merge_keys.merge(field->part_of_key);
field_table->used_fields++;
}