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Bug#16540042: WRONG QUERY RESULT WHEN USING RANGE OVER

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PARTIAL INDEX

Consider the following table definition:

CREATE TABLE t (
  my_col CHAR(10),
  ...
  INDEX my_idx (my_col(1))
)

The my_idx index is not able to distinguish between rows with
equal first-character my_col-values (e.g. "f", "foo", "fee").

Prior to this CS, the range optimizer would translate

"WHERE my_col NOT IN ('f', 'h')" into (optimizer trace syntax)

"ranges": [
  "NULL < my_col < f",
  "f < my_col"
]

But this was not correct because the rows with values "foo" 
and "fee" would not belong to any of those ranges. However, the
predicate "my_col != 'f' AND my_col != 'h'" would translate
to 

"ranges": [
  "NULL < my_col"
]

because get_mm_leaf() changes from "<" to "<=" for partial
keyparts. This CS changes the range optimizer implementation 
for NOT IN to behave like a conjunction of NOT EQUAL: it 
replaces "<" with "<=" for all but the first range when the
keypart is partial.
This commit is contained in:
Jorgen Loland
2013-04-12 09:39:56 +02:00
parent d20ec0f5ba
commit 2c780b461d
1 changed files with 29 additions and 0 deletions
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29
sql/opt_range.cc
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@ -5345,6 +5345,34 @@ static SEL_TREE *get_func_mm_tree(RANGE_OPT_PARAM *param, Item_func *cond_func,
{
new_interval->min_value= last_val->max_value;
new_interval->min_flag= NEAR_MIN;
/*
If the interval is over a partial keypart, the
interval must be "c_{i-1} <= X < c_i" instead of
"c_{i-1} < X < c_i". Reason:
Consider a table with a column "my_col VARCHAR(3)",
and an index with definition
"INDEX my_idx my_col(1)". If the table contains rows
with my_col values "f" and "foo", the index will not
distinguish the two rows.
Note that tree_or() below will effectively merge
this range with the range created for c_{i-1} and
we'll eventually end up with only one range:
"NULL < X".
Partitioning indexes are never partial.
*/
if (param->using_real_indexes)
{
const KEY key=
param->table->key_info[param->real_keynr[idx]];
const KEY_PART_INFO *kpi= key.key_part + new_interval->part;
if (kpi->key_part_flag & HA_PART_KEY_SEG)
new_interval->min_flag= 0;
}
}
}
/*
@ -5827,6 +5855,7 @@ get_mm_leaf(RANGE_OPT_PARAM *param, COND *conf_func, Field *field,
if (key_part->image_type == Field::itMBR)
{
// @todo: use is_spatial_operator() instead?
switch (type) {
case Item_func::SP_EQUALS_FUNC:
case Item_func::SP_DISJOINT_FUNC: