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MDEV-21958: Query having many NOT-IN clauses running forever

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Basic variant of the fix: do not consider conditions in form

  unique_key NOT IN (c1,c2...)

to be sargable. If there are only a few constants, the condition
is not selective. If there are a lot constants, the overhead of
processing such a huge range list is not worth it.

(Backport to 10.2)
This commit is contained in:
Sergei Petrunia
2020-12-15 14:38:30 +03:00
parent ac9c6f53a5
commit 066212d16c
3 changed files with 60 additions and 0 deletions
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24
sql/opt_range.cc
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@ -7158,6 +7158,30 @@ SEL_TREE *Item_func_in::get_func_mm_tree(RANGE_OPT_PARAM *param,
if (array->count > NOT_IN_IGNORE_THRESHOLD || !value_item)
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 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
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.next_bit()) != key_map::Iterator::BITMAP_END)
{
KEY *key_info= &param->table->key_info[key_no];
if (key_info->user_defined_key_parts == 1 &&
(key_info->flags & HA_NOSAME))
{
DBUG_RETURN(0);
}
}
}
/* Get a SEL_TREE for "(-inf|NULL) < X < c_0" interval. */
uint i=0;
do