database/mariadb
1
0
Fork 0
mirror of https://github.com/MariaDB/server.git synced 2025-08-01 03:47:19 +03:00
Code Activity

MDEV-23634: Select query hanged the server and leads to OOM ...

Browse Source 
Handle "col<>const" in the same way that MDEV-21958 did for
"col NOT IN(const-list)": do not use the condition for range/index_merge
accesses if there is a unique UNIQUE KEY(col).

The testcase is in main/range.test. The rest of test updates are
due to widespread use of 'pk<>1' in the testsuite. Changed the test
to use different but equivalent forms of the conditions.
This commit is contained in:
Sergei Petrunia
2021-04-08 17:25:02 +03:00
parent 4e2ca42225
commit c03841ec0e
21 changed files with 142 additions and 74 deletions
Download Patch File Download Diff File Expand all files Collapse all files

70
sql/opt_range.cc
View File

@ -449,6 +449,7 @@ void print_range_for_non_indexed_field(String *out, Field *field,
static void print_min_range_operator(String *out, const ha_rkey_function flag);
static void print_max_range_operator(String *out, const ha_rkey_function flag);
static bool is_field_an_unique_index(RANGE_OPT_PARAM *param, Field *field);
/*
SEL_IMERGE is a list of possible ways to do index merge, i.e. it is
@ -7689,6 +7690,21 @@ SEL_TREE *Item_bool_func::get_ne_mm_tree(RANGE_OPT_PARAM *param,
}
SEL_TREE *Item_func_ne::get_func_mm_tree(RANGE_OPT_PARAM *param,
Field *field, Item *value)
{
DBUG_ENTER("Item_func_ne::get_func_mm_tree");
/*
If this condition is a "col1<>...", where there is a UNIQUE KEY(col1),
do not construct a SEL_TREE from it. A condition that excludes just one
row in the table is not selective (unless there are only a few rows)
*/
if (is_field_an_unique_index(param, field))
DBUG_RETURN(NULL);
DBUG_RETURN(get_ne_mm_tree(param, field, value, value));
}
SEL_TREE *Item_func_between::get_func_mm_tree(RANGE_OPT_PARAM *param,
Field *field, Item *value)
{
@ -7787,28 +7803,16 @@ SEL_TREE *Item_func_in::get_func_mm_tree(RANGE_OPT_PARAM *param,
DBUG_RETURN(0);
/*
If this is "unique_key NOT IN (...)", do not consider it sargable (for
any index, not just the unique one). The logic is as follows:
if this is a "col1 NOT IN (...)", and there is a UNIQUE KEY(col1), do
not constuct a SEL_TREE from it. The rationale is as follows:
- if there are only a few constants, this condition is not selective
(unless the table is also very small in which case we won't gain
anything)
- If there are a lot of constants, the overhead of building and
- if there are a lot of constants, the overhead of building and
processing enormous range list is not worth it.
*/
if (param->using_real_indexes)
{
key_map::Iterator it(field->key_start);
uint key_no;
while ((key_no= it++) != key_map::Iterator::BITMAP_END)
{
KEY *key_info= &field->table->key_info[key_no];
if (key_info->user_defined_key_parts == 1 &&
(key_info->flags & HA_NOSAME))
{
DBUG_RETURN(0);
}
}
}
if (is_field_an_unique_index(param, field))
DBUG_RETURN(0);
/* Get a SEL_TREE for "(-inf|NULL) < X < c_0" interval. */
uint i=0;
@ -8526,6 +8530,38 @@ SEL_TREE *Item_equal::get_mm_tree(RANGE_OPT_PARAM *param, Item **cond_ptr)
}
/*
@brief
Check if there is an one-segment unique key that matches the field exactly
@detail
In the future we could also add "almost unique" indexes where any value is
present only in a few rows (but necessarily exactly one row)
*/
static bool is_field_an_unique_index(RANGE_OPT_PARAM *param, Field *field)
{
DBUG_ENTER("is_field_an_unique_index");
// The check for using_real_indexes is there because of the heuristics
// this function is used for.
if (param->using_real_indexes)
{
key_map::Iterator it(field->key_start);
uint key_no;
while ((key_no= it++) != key_map::Iterator::BITMAP_END)
{
KEY *key_info= &field->table->key_info[key_no];
if (key_info->user_defined_key_parts == 1 &&
(key_info->flags & HA_NOSAME))
{
DBUG_RETURN(true);
}
}
}
DBUG_RETURN(false);
}
SEL_TREE *
Item_bool_func::get_mm_parts(RANGE_OPT_PARAM *param, Field *field,
Item_func::Functype type, Item *value)