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Commit caf31114 authored by unknown's avatar unknown
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Merged the fix for bug lp:1009187, mdev-373

parents 0704d470 0bc89929
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mysql-test/r/subselect4.result
View file @ caf31114
......@@ -206,6 +206,165 @@ default(a)
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
DROP TABLE t;
#
# LP BUG#1009187, MDEV-373, MYSQL bug#58628
# Wrong result for a query with [NOT] IN subquery predicate if
# the left part of the predicate is explicit NULL
#
CREATE TABLE t1 (pk INT NOT NULL, i INT NOT NULL);
INSERT INTO t1 VALUES (0,10), (1,20), (2,30), (3,40);
CREATE TABLE t2a (pk INT NOT NULL, i INT NOT NULL, PRIMARY KEY(i,pk));
INSERT INTO t2a VALUES (0,0), (1,1), (2,2), (3,3);
CREATE TABLE t2b (pk INT, i INT);
INSERT INTO t2b VALUES (0,0), (1,1), (2,2), (3,3);
CREATE TABLE t2c (pk INT NOT NULL, i INT NOT NULL);
INSERT INTO t2c VALUES (0,0), (1,1), (2,2), (3,3);
create index it2c on t2c (i,pk);
CREATE TABLE t2d (pk INT NOT NULL, i INT NOT NULL, PRIMARY KEY(i));
INSERT INTO t2d VALUES (0,0), (1,1), (2,2), (3,3);
EXPLAIN
SELECT * FROM t1 WHERE NULL NOT IN (SELECT t2a.i FROM t2a WHERE t2a.pk = t1.pk);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 4 Using where
2 DEPENDENT SUBQUERY t2a unique_subquery PRIMARY PRIMARY 8 const,test.t1.pk 1 Using index; Using where; Full scan on NULL key
SELECT * FROM t1 WHERE NULL NOT IN (SELECT t2a.i FROM t2a WHERE t2a.pk = t1.pk);
pk i
SELECT * FROM t1 WHERE 1+NULL NOT IN (SELECT t2a.i FROM t2a WHERE t2a.pk = t1.pk);
pk i
SELECT * FROM t1 WHERE NULL IN (SELECT t2a.i FROM t2a WHERE t2a.pk = t1.pk) IS UNKNOWN;
pk i
0 10
1 20
2 30
3 40
SELECT t1.pk, NULL NOT IN (SELECT t2a.i FROM t2a WHERE t2a.pk = t1.pk) FROM t1;
pk NULL NOT IN (SELECT t2a.i FROM t2a WHERE t2a.pk = t1.pk)
0 NULL
1 NULL
2 NULL
3 NULL
EXPLAIN
SELECT * FROM t1 WHERE NULL NOT IN (SELECT t2b.i FROM t2b WHERE t2b.pk = t1.pk);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 4 Using where
2 DEPENDENT SUBQUERY t2b ALL NULL NULL NULL NULL 4 Using where
SELECT * FROM t1 WHERE NULL NOT IN (SELECT t2b.i FROM t2b WHERE t2b.pk = t1.pk);
pk i
SELECT * FROM t1 WHERE NULL IN (SELECT t2b.i FROM t2b WHERE t2b.pk = t1.pk) IS UNKNOWN;
pk i
0 10
1 20
2 30
3 40
SELECT t1.pk, NULL NOT IN (SELECT t2b.i FROM t2b WHERE t2b.pk = t1.pk) FROM t1;
pk NULL NOT IN (SELECT t2b.i FROM t2b WHERE t2b.pk = t1.pk)
0 NULL
1 NULL
2 NULL
3 NULL
EXPLAIN
SELECT * FROM t1 WHERE NULL NOT IN (SELECT t2c.i FROM t2c WHERE t2c.pk = t1.pk);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 4 Using where
2 DEPENDENT SUBQUERY t2c index_subquery it2c it2c 8 const,test.t1.pk 2 Using index; Using where; Full scan on NULL key
SELECT * FROM t1 WHERE NULL NOT IN (SELECT t2c.i FROM t2c WHERE t2c.pk = t1.pk);
pk i
SELECT * FROM t1 WHERE NULL IN (SELECT t2c.i FROM t2c WHERE t2c.pk = t1.pk) IS UNKNOWN;
pk i
0 10
1 20
2 30
3 40
SELECT t1.pk, NULL NOT IN (SELECT t2c.i FROM t2c WHERE t2c.pk = t1.pk) FROM t1;
pk NULL NOT IN (SELECT t2c.i FROM t2c WHERE t2c.pk = t1.pk)
0 NULL
1 NULL
2 NULL
3 NULL
EXPLAIN
SELECT * FROM t1 WHERE NULL NOT IN (SELECT t2d.i FROM t2d WHERE t2d.pk = t1.pk);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 4 Using where
2 DEPENDENT SUBQUERY t2d const PRIMARY PRIMARY 4 const 1 Using where; Full scan on NULL key
SELECT * FROM t1 WHERE NULL NOT IN (SELECT t2d.i FROM t2d WHERE t2d.pk = t1.pk);
pk i
SELECT * FROM t1 WHERE NULL IN (SELECT t2d.i FROM t2d WHERE t2d.pk = t1.pk) IS UNKNOWN;
pk i
0 10
1 20
2 30
3 40
SELECT t1.pk, NULL NOT IN (SELECT t2d.i FROM t2d WHERE t2d.pk = t1.pk) FROM t1;
pk NULL NOT IN (SELECT t2d.i FROM t2d WHERE t2d.pk = t1.pk)
0 NULL
1 NULL
2 NULL
3 NULL
EXPLAIN
SELECT * FROM t1 WHERE (NULL, 1) NOT IN (SELECT t2a.i, t2a.pk FROM t2a WHERE t2a.pk = t1.pk);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 4 Using where
2 DEPENDENT SUBQUERY t2a eq_ref PRIMARY PRIMARY 8 const,test.t1.pk 1 Using where; Using index; Full scan on NULL key
SELECT * FROM t1 WHERE (NULL, 1) NOT IN (SELECT t2a.i, t2a.pk FROM t2a WHERE t2a.pk = t1.pk);
pk i
0 10
2 30
3 40
SELECT (NULL, 1) NOT IN (SELECT t2a.i, t2a.pk FROM t2a WHERE t2a.pk = t1.pk) from t1;
(NULL, 1) NOT IN (SELECT t2a.i, t2a.pk FROM t2a WHERE t2a.pk = t1.pk)
1
NULL
1
1
EXPLAIN
SELECT * FROM t1 WHERE (NULL, 1) NOT IN (SELECT t2b.i, t2b.pk FROM t2b WHERE t2b.pk = t1.pk);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 4 Using where
2 DEPENDENT SUBQUERY t2b ALL NULL NULL NULL NULL 4 Using where
SELECT * FROM t1 WHERE (NULL, 1) NOT IN (SELECT t2b.i, t2b.pk FROM t2b WHERE t2b.pk = t1.pk);
pk i
0 10
2 30
3 40
SELECT (NULL, 1) NOT IN (SELECT t2b.i, t2b.pk FROM t2b WHERE t2b.pk = t1.pk) from t1;
(NULL, 1) NOT IN (SELECT t2b.i, t2b.pk FROM t2b WHERE t2b.pk = t1.pk)
1
NULL
1
1
EXPLAIN
SELECT * FROM t1 WHERE (NULL, 1) NOT IN (SELECT t2c.i, t2c.pk FROM t2c WHERE t2c.pk = t1.pk);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 4 Using where
2 DEPENDENT SUBQUERY t2c ref it2c it2c 8 const,test.t1.pk 2 Using where; Using index; Full scan on NULL key
SELECT * FROM t1 WHERE (NULL, 1) NOT IN (SELECT t2c.i, t2c.pk FROM t2c WHERE t2c.pk = t1.pk);
pk i
0 10
2 30
3 40
SELECT (NULL, 1) NOT IN (SELECT t2c.i, t2c.pk FROM t2c WHERE t2c.pk = t1.pk) from t1;
(NULL, 1) NOT IN (SELECT t2c.i, t2c.pk FROM t2c WHERE t2c.pk = t1.pk)
1
NULL
1
1
EXPLAIN
SELECT * FROM t1 WHERE (NULL, 1) NOT IN (SELECT t2d.i, t2d.pk FROM t2d WHERE t2d.pk = t1.pk);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 4 Using where
2 DEPENDENT SUBQUERY t2d const PRIMARY PRIMARY 4 const 1 Using where; Full scan on NULL key
SELECT * FROM t1 WHERE (NULL, 1) NOT IN (SELECT t2d.i, t2d.pk FROM t2d WHERE t2d.pk = t1.pk);
pk i
0 10
2 30
3 40
SELECT (NULL, 1) NOT IN (SELECT t2d.i, t2d.pk FROM t2d WHERE t2d.pk = t1.pk) from t1;
(NULL, 1) NOT IN (SELECT t2d.i, t2d.pk FROM t2d WHERE t2d.pk = t1.pk)
1
NULL
1
1
drop table t1, t2a, t2b, t2c, t2d;
#
# End of 5.1 tests.
#
#
......
mysql-test/t/subselect4.test
View file @ caf31114
......@@ -184,6 +184,75 @@ INSERT INTO t VALUES (''),(''),(''),(''),(''),(''),(''),(''),(''),(''),('');
SELECT * FROM (SELECT default(a) FROM t GROUP BY a) d;
DROP TABLE t;
--echo #
--echo # LP BUG#1009187, MDEV-373, MYSQL bug#58628
--echo # Wrong result for a query with [NOT] IN subquery predicate if
--echo # the left part of the predicate is explicit NULL
--echo #
CREATE TABLE t1 (pk INT NOT NULL, i INT NOT NULL);
INSERT INTO t1 VALUES (0,10), (1,20), (2,30), (3,40);
CREATE TABLE t2a (pk INT NOT NULL, i INT NOT NULL, PRIMARY KEY(i,pk));
INSERT INTO t2a VALUES (0,0), (1,1), (2,2), (3,3);
CREATE TABLE t2b (pk INT, i INT);
INSERT INTO t2b VALUES (0,0), (1,1), (2,2), (3,3);
CREATE TABLE t2c (pk INT NOT NULL, i INT NOT NULL);
INSERT INTO t2c VALUES (0,0), (1,1), (2,2), (3,3);
create index it2c on t2c (i,pk);
CREATE TABLE t2d (pk INT NOT NULL, i INT NOT NULL, PRIMARY KEY(i));
INSERT INTO t2d VALUES (0,0), (1,1), (2,2), (3,3);
EXPLAIN
SELECT * FROM t1 WHERE NULL NOT IN (SELECT t2a.i FROM t2a WHERE t2a.pk = t1.pk);
SELECT * FROM t1 WHERE NULL NOT IN (SELECT t2a.i FROM t2a WHERE t2a.pk = t1.pk);
SELECT * FROM t1 WHERE 1+NULL NOT IN (SELECT t2a.i FROM t2a WHERE t2a.pk = t1.pk);
SELECT * FROM t1 WHERE NULL IN (SELECT t2a.i FROM t2a WHERE t2a.pk = t1.pk) IS UNKNOWN;
SELECT t1.pk, NULL NOT IN (SELECT t2a.i FROM t2a WHERE t2a.pk = t1.pk) FROM t1;
EXPLAIN
SELECT * FROM t1 WHERE NULL NOT IN (SELECT t2b.i FROM t2b WHERE t2b.pk = t1.pk);
SELECT * FROM t1 WHERE NULL NOT IN (SELECT t2b.i FROM t2b WHERE t2b.pk = t1.pk);
SELECT * FROM t1 WHERE NULL IN (SELECT t2b.i FROM t2b WHERE t2b.pk = t1.pk) IS UNKNOWN;
SELECT t1.pk, NULL NOT IN (SELECT t2b.i FROM t2b WHERE t2b.pk = t1.pk) FROM t1;
EXPLAIN
SELECT * FROM t1 WHERE NULL NOT IN (SELECT t2c.i FROM t2c WHERE t2c.pk = t1.pk);
SELECT * FROM t1 WHERE NULL NOT IN (SELECT t2c.i FROM t2c WHERE t2c.pk = t1.pk);
SELECT * FROM t1 WHERE NULL IN (SELECT t2c.i FROM t2c WHERE t2c.pk = t1.pk) IS UNKNOWN;
SELECT t1.pk, NULL NOT IN (SELECT t2c.i FROM t2c WHERE t2c.pk = t1.pk) FROM t1;
EXPLAIN
SELECT * FROM t1 WHERE NULL NOT IN (SELECT t2d.i FROM t2d WHERE t2d.pk = t1.pk);
SELECT * FROM t1 WHERE NULL NOT IN (SELECT t2d.i FROM t2d WHERE t2d.pk = t1.pk);
SELECT * FROM t1 WHERE NULL IN (SELECT t2d.i FROM t2d WHERE t2d.pk = t1.pk) IS UNKNOWN;
SELECT t1.pk, NULL NOT IN (SELECT t2d.i FROM t2d WHERE t2d.pk = t1.pk) FROM t1;
EXPLAIN
SELECT * FROM t1 WHERE (NULL, 1) NOT IN (SELECT t2a.i, t2a.pk FROM t2a WHERE t2a.pk = t1.pk);
SELECT * FROM t1 WHERE (NULL, 1) NOT IN (SELECT t2a.i, t2a.pk FROM t2a WHERE t2a.pk = t1.pk);
SELECT (NULL, 1) NOT IN (SELECT t2a.i, t2a.pk FROM t2a WHERE t2a.pk = t1.pk) from t1;
EXPLAIN
SELECT * FROM t1 WHERE (NULL, 1) NOT IN (SELECT t2b.i, t2b.pk FROM t2b WHERE t2b.pk = t1.pk);
SELECT * FROM t1 WHERE (NULL, 1) NOT IN (SELECT t2b.i, t2b.pk FROM t2b WHERE t2b.pk = t1.pk);
SELECT (NULL, 1) NOT IN (SELECT t2b.i, t2b.pk FROM t2b WHERE t2b.pk = t1.pk) from t1;
EXPLAIN
SELECT * FROM t1 WHERE (NULL, 1) NOT IN (SELECT t2c.i, t2c.pk FROM t2c WHERE t2c.pk = t1.pk);
SELECT * FROM t1 WHERE (NULL, 1) NOT IN (SELECT t2c.i, t2c.pk FROM t2c WHERE t2c.pk = t1.pk);
SELECT (NULL, 1) NOT IN (SELECT t2c.i, t2c.pk FROM t2c WHERE t2c.pk = t1.pk) from t1;
EXPLAIN
SELECT * FROM t1 WHERE (NULL, 1) NOT IN (SELECT t2d.i, t2d.pk FROM t2d WHERE t2d.pk = t1.pk);
SELECT * FROM t1 WHERE (NULL, 1) NOT IN (SELECT t2d.i, t2d.pk FROM t2d WHERE t2d.pk = t1.pk);
SELECT (NULL, 1) NOT IN (SELECT t2d.i, t2d.pk FROM t2d WHERE t2d.pk = t1.pk) from t1;
drop table t1, t2a, t2b, t2c, t2d;
--echo #
--echo # End of 5.1 tests.
--echo #
......
sql/item_subselect.cc
View file @ caf31114
......@@ -734,6 +734,19 @@ bool Item_subselect::expr_cache_is_needed(THD *thd)
}
/**
Check if the left IN argument contains NULL values.
@retval TRUE there are NULLs
@retval FALSE otherwise
*/
inline bool Item_in_subselect::left_expr_has_null()
{
return (*(optimizer->get_cache()))->null_value;
}
/**
Check if an expression cache is needed for this subquery
......@@ -3285,161 +3298,51 @@ int subselect_uniquesubquery_engine::scan_table()
}
/*
Copy ref key and check for null parts in it
SYNOPSIS
subselect_uniquesubquery_engine::copy_ref_key()
DESCRIPTION
Copy ref key and check for null parts in it.
Depending on the nullability and conversion problems this function
recognizes and processes the following states :
1. Partial match on top level. This means IN has a value of FALSE
regardless of the data in the subquery table.
Detected by finding a NULL in the left IN operand of a top level
expression.
We may actually skip reading the subquery, so return TRUE to skip
the table scan in subselect_uniquesubquery_engine::exec and make
the value of the IN predicate a NULL (that is equal to FALSE on
top level).
2. No exact match when IN is nested inside another predicate.
Detected by finding a NULL in the left IN operand when IN is not
a top level predicate.
We cannot have an exact match. But we must proceed further with a
table scan to find out if it's a partial match (and IN has a value
of NULL) or no match (and IN has a value of FALSE).
So we return FALSE to continue with the scan and see if there are
any record that would constitute a partial match (as we cannot
determine that from the index).
3. Error converting the left IN operand to the column type of the
right IN operand. This counts as no match (and IN has the value of
FALSE). We mark the subquery table cursor as having no more rows
(to ensure that the processing that follows will not find a match)
and return FALSE, so IN is not treated as returning NULL.
/**
Copy ref key for index access into the only subquery table.
@details
Copy ref key and check for conversion problems.
If there is an error converting the left IN operand to the column type of
the right IN operand count it as no match. In this case IN has the value of
FALSE. We mark the subquery table cursor as having no more rows (to ensure
that the processing that follows will not find a match) and return FALSE,
so IN is not treated as returning NULL.
RETURN
FALSE - The value of the IN predicate is not known. Proceed to find the
value of the IN predicate using the determined values of
null_keypart and table->status.
TRUE - IN predicate has a value of NULL. Stop the processing right there
and return NULL to the outer predicates.
@returns
@retval FALSE The outer ref was copied into an index lookup key.
@retval TRUE The outer ref cannot possibly match any row, IN is FALSE.
*/
bool subselect_uniquesubquery_engine::copy_ref_key()
bool subselect_uniquesubquery_engine::copy_ref_key(bool skip_constants)
{
DBUG_ENTER("subselect_uniquesubquery_engine::copy_ref_key");
for (store_key **copy= tab->ref.key_copy ; *copy ; copy++)
{
if ((*copy)->store_key_is_const())
continue;
tab->ref.key_err= (*copy)->copy();
/*
When there is a NULL part in the key we don't need to make index
lookup for such key thus we don't need to copy whole key.
If we later should do a sequential scan return OK. Fail otherwise.
See also the comment for the subselect_uniquesubquery_engine::exec()
function.
*/
null_keypart= (*copy)->null_key;
if (null_keypart)
{
bool top_level= ((Item_in_subselect *) item)->is_top_level_item();
if (top_level)
{
/* Partial match on top level */
DBUG_RETURN(1);
}
else
{
/* No exact match when IN is nested inside another predicate */
break;
}
}
/*
Check if the error is equal to STORE_KEY_FATAL. This is not expressed
using the store_key::store_key_result enum because ref.key_err is a
boolean and we want to detect both TRUE and STORE_KEY_FATAL from the
space of the union of the values of [TRUE, FALSE] and
store_key::store_key_result.
TODO: fix the variable an return types.
*/
if (tab->ref.key_err & 1)
{
/*
Error converting the left IN operand to the column type of the right
IN operand.
*/
tab->table->status= STATUS_NOT_FOUND;
break;
}
}
DBUG_RETURN(0);
}
/*
@retval 1 A NULL was found in the outer reference, index lookup is
not applicable, the outer ref is unsusable as a lookup key,
use some other method to find a match.
@retval 0 The outer ref was copied into an index lookup key.
@retval -1 The outer ref cannot possibly match any row, IN is FALSE.
*/
/* TIMOUR: this method is a variant of copy_ref_key(), needs refactoring. */
int subselect_uniquesubquery_engine::copy_ref_key_simple()
{
for (store_key **copy= tab->ref.key_copy ; *copy ; copy++)
{
enum store_key::store_key_result store_res;
if (skip_constants && (*copy)->store_key_is_const())
continue;
store_res= (*copy)->copy();
tab->ref.key_err= store_res;
/*
When there is a NULL part in the key we don't need to make index
lookup for such key thus we don't need to copy whole key.
If we later should do a sequential scan return OK. Fail otherwise.
See also the comment for the subselect_uniquesubquery_engine::exec()
function.
*/
null_keypart= (*copy)->null_key;
if (null_keypart)
return 1;
/*
Check if the error is equal to STORE_KEY_FATAL. This is not expressed
using the store_key::store_key_result enum because ref.key_err is a
boolean and we want to detect both TRUE and STORE_KEY_FATAL from the
space of the union of the values of [TRUE, FALSE] and
store_key::store_key_result.
TODO: fix the variable an return types.
*/
if (store_res == store_key::STORE_KEY_FATAL)
{
/*
Error converting the left IN operand to the column type of the right
IN operand.
*/
return -1;
DBUG_RETURN(true);
}
}
return 0;
DBUG_RETURN(false);
}
/*
Execute subselect
SYNOPSIS
subselect_uniquesubquery_engine::exec()
/**
Execute subselect via unique index lookup
DESCRIPTION
@details
Find rows corresponding to the ref key using index access.
If some part of the lookup key is NULL, then we're evaluating
NULL IN (SELECT ... )
......@@ -3456,11 +3359,11 @@ int subselect_uniquesubquery_engine::copy_ref_key_simple()
The result of this function (info about whether a row was found) is
stored in this->empty_result_set.
NOTE
RETURN
FALSE - ok
TRUE - an error occured while scanning
@returns
@retval 0 OK
@retval 1 notify caller to call Item_subselect::reset(),
in most cases reset() sets the result to NULL
*/
int subselect_uniquesubquery_engine::exec()
......@@ -3470,32 +3373,30 @@ int subselect_uniquesubquery_engine::exec()
TABLE *table= tab->table;
empty_result_set= TRUE;
table->status= 0;
Item_in_subselect *in_subs= (Item_in_subselect *) item;
if (!tab->preread_init_done && tab->preread_init())
DBUG_RETURN(1);
/* TODO: change to use of 'full_scan' here? */
if (copy_ref_key())
if (in_subs->left_expr_has_null())
{
/*
TIMOUR: copy_ref_key() == 1 means NULL result, not error, why return 1?
Check who reiles on this result.
The case when all values in left_expr are NULL is handled by
Item_in_optimizer::val_int().
*/
DBUG_RETURN(1);
if (in_subs->is_top_level_item())
DBUG_RETURN(1); /* notify caller to call reset() and set NULL value. */
else
DBUG_RETURN(scan_table());
}
if (table->status)
if (copy_ref_key(true))
{
/*
We know that there will be no rows even if we scan.
Can be set in copy_ref_key.
*/
((Item_in_subselect *) item)->value= 0;
/* We know that there will be no rows even if we scan. */
in_subs->value= 0;
DBUG_RETURN(0);
}
if (!tab->preread_init_done && tab->preread_init())
DBUG_RETURN(1);
if (null_keypart)
DBUG_RETURN(scan_table());
if (!table->file->inited)
table->file->ha_index_init(tab->ref.key, 0);
error= table->file->ha_index_read_map(table->record[0],
......@@ -3571,14 +3472,10 @@ subselect_uniquesubquery_engine::~subselect_uniquesubquery_engine()
}
/*
Index-lookup subselect 'engine' - run the subquery
SYNOPSIS
subselect_indexsubquery_engine:exec()
full_scan
/**
Execute subselect via unique index lookup
DESCRIPTION
@details
The engine is used to resolve subqueries in form
oe IN (SELECT key FROM tbl WHERE subq_where)
......@@ -3593,7 +3490,7 @@ subselect_uniquesubquery_engine::~subselect_uniquesubquery_engine()
row that satisfies subq_where. If found, return NULL, otherwise
return FALSE.
TODO
@todo
The step #1 can be optimized further when the index has several key
parts. Consider a subquery:
......@@ -3618,9 +3515,10 @@ subselect_uniquesubquery_engine::~subselect_uniquesubquery_engine()
cheaper. We can use index statistics to quickly check whether "ref" scan
will be cheaper than full table scan.
RETURN
0
1
@returns
@retval 0 OK
@retval 1 notify caller to call Item_subselect::reset(),
in most cases reset() sets the result to NULL
*/
int subselect_indexsubquery_engine::exec()
......@@ -3629,10 +3527,10 @@ int subselect_indexsubquery_engine::exec()
int error;
bool null_finding= 0;
TABLE *table= tab->table;
Item_in_subselect *in_subs= (Item_in_subselect *) item;
((Item_in_subselect *) item)->value= 0;
empty_result_set= TRUE;
null_keypart= 0;
table->status= 0;
if (check_null)
......@@ -3642,25 +3540,27 @@ int subselect_indexsubquery_engine::exec()
((Item_in_subselect *) item)->was_null= 0;
}
/* Copy the ref key and check for nulls... */
if (copy_ref_key())
if (!tab->preread_init_done && tab->preread_init())
DBUG_RETURN(1);
if (table->status)
if (in_subs->left_expr_has_null())
{
/*
We know that there will be no rows even if we scan.
Can be set in copy_ref_key.
/*
The case when all values in left_expr are NULL is handled by
Item_in_optimizer::val_int().
*/
((Item_in_subselect *) item)->value= 0;
DBUG_RETURN(0);
if (in_subs->is_top_level_item())
DBUG_RETURN(1); /* notify caller to call reset() and set NULL value. */
else
DBUG_RETURN(scan_table());
}
if (!tab->preread_init_done && tab->preread_init())
DBUG_RETURN(1);
if (null_keypart)
DBUG_RETURN(scan_table());
if (copy_ref_key(true))
{
/* We know that there will be no rows even if we scan. */
in_subs->value= 0;
DBUG_RETURN(0);
}
if (!table->file->inited)
table->file->ha_index_init(tab->ref.key, 1);
......@@ -5429,37 +5329,42 @@ subselect_partial_match_engine::subselect_partial_match_engine(
int subselect_partial_match_engine::exec()
{
Item_in_subselect *item_in= (Item_in_subselect *) item;
int copy_res, lookup_res;
int lookup_res;
/* Try to find a matching row by index lookup. */
copy_res= lookup_engine->copy_ref_key_simple();
if (copy_res == -1)
{
/* The result is FALSE based on the outer reference. */
item_in->value= 0;
item_in->null_value= 0;
return 0;
}
else if (copy_res == 0)
DBUG_ASSERT(!(item_in->left_expr_has_null() &&
item_in->is_top_level_item()));
if (!item_in->left_expr_has_null())
{
/* Search for a complete match. */
if ((lookup_res= lookup_engine->index_lookup()))
/* Try to find a matching row by index lookup. */
if (lookup_engine->copy_ref_key(false))
{
/* An error occured during lookup(). */
/* The result is FALSE based on the outer reference. */
item_in->value= 0;
item_in->null_value= 0;
return lookup_res;
return 0;
}
else if (item_in->value || !count_columns_with_nulls)
else
{
/*
A complete match was found, the result of IN is TRUE.
If no match was found, and there are no NULLs in the materialized
subquery, then the result is guaranteed to be false because this
branch is executed when the outer reference has no NULLs as well.
Notice: (this->item == lookup_engine->item)
*/
return 0;
/* Search for a complete match. */
if ((lookup_res= lookup_engine->index_lookup()))
{
/* An error occured during lookup(). */
item_in->value= 0;
item_in->null_value= 0;
return lookup_res;
}
else if (item_in->value || !count_columns_with_nulls)
{
/*
A complete match was found, the result of IN is TRUE.
If no match was found, and there are no NULLs in the materialized
subquery, then the result is guaranteed to be false because this
branch is executed when the outer reference has no NULLs as well.
Notice: (this->item == lookup_engine->item)
*/
return 0;
}
}
}
......
sql/item_subselect.h
View file @ caf31114
......@@ -591,6 +591,7 @@ class Item_in_subselect :public Item_exists_subselect
/* Inform 'this' that it was computed, and contains a valid result. */
void set_first_execution() { if (first_execution) first_execution= FALSE; }
bool expr_cache_is_needed(THD *thd);
inline bool left_expr_has_null();
int optimize(double *out_rows, double *cost);
/*
......@@ -869,7 +870,6 @@ class subselect_uniquesubquery_engine: public subselect_engine
expression is NULL.
*/
bool empty_result_set;
bool null_keypart; /* TRUE <=> constructed search tuple has a NULL */
public:
// constructor can assign THD because it will be called after JOIN::prepare
......@@ -893,8 +893,7 @@ class subselect_uniquesubquery_engine: public subselect_engine
bool no_tables();
int index_lookup(); /* TIMOUR: this method needs refactoring. */
int scan_table();
bool copy_ref_key();
int copy_ref_key_simple(); /* TIMOUR: this method needs refactoring. */
bool copy_ref_key(bool skip_constants);
bool no_rows() { return empty_result_set; }
virtual enum_engine_type engine_type() { return UNIQUESUBQUERY_ENGINE; }
};
......
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