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Fixed bug mdev-11608.

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The fix for bug mdev-11488 introduced the virtual method
convert_to_basic_const_item for the class Item_cache.
The implementation of this method for the class Item_cache_str
was not quite correct: the server could crash if the cached item
was null.
A similar problem could appear for the implementation of
this method for the class Item_cache_decimal. Although I could not
reproduce the problem I decided to change the code appropriately.
This commit is contained in:
Igor Babaev
2016-12-20 11:08:50 -08:00
parent 95228dc80b
commit 9b27d3e86e
3 changed files with 104 additions and 8 deletions
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63
mysql-test/r/derived_cond_pushdown.result
View File

@ -8178,3 +8178,66 @@ EXPLAIN
}
DROP VIEW v1;
DROP TABLE t1;
#
# MDEV-11608: pushdown of the predicate with cached null value
#
CREATE TABLE t1 (c VARCHAR(3));
CREATE ALGORITHM=TEMPTABLE VIEW v1 AS SELECT * FROM t1;
INSERT INTO t1 VALUES ('foo'),('bar');
CREATE TABLE t2 (c VARCHAR(3));
INSERT INTO t2 VALUES ('foo'),('xyz');
SELECT * FROM v1 WHERE v1.c IN ( SELECT MIN(c) FROM t2 WHERE 0 );
c
EXPLAIN FORMAT=JSON
SELECT * FROM v1 WHERE v1.c IN ( SELECT MIN(c) FROM t2 WHERE 0 );
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"table_name": "<subquery2>",
"access_type": "system",
"rows": 1,
"filtered": 100,
"materialized": {
"unique": 1,
"query_block": {
"select_id": 2,
"table": {
"message": "Impossible WHERE"
}
}
}
},
"table": {
"table_name": "<derived3>",
"access_type": "ALL",
"rows": 2,
"filtered": 100,
"attached_condition": "v1.c = NULL",
"materialized": {
"query_block": {
"select_id": 3,
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows": 2,
"filtered": 100,
"attached_condition": "t1.c = NULL"
}
}
}
}
}
}
DROP VIEW v1;
DROP TABLE t1,t2;
CREATE TABLE t1 (d DECIMAL(10,2));
CREATE ALGORITHM=TEMPTABLE VIEW v1 AS SELECT * FROM t1;
INSERT INTO t1 VALUES (5.37),(1.1);
CREATE TABLE t2 (d DECIMAL(10,2));
INSERT INTO t2 VALUES ('1.1'),('2.23');
SELECT * FROM v1 WHERE v1.d IN ( SELECT MIN(d) FROM t2 WHERE 0 );
d
DROP VIEW v1;
DROP TABLE t1,t2;

30
mysql-test/t/derived_cond_pushdown.test
View File

@ -1289,3 +1289,33 @@ SELECT * FROM v1 WHERE NULLIF(1, i);
DROP VIEW v1;
DROP TABLE t1;
--echo #
--echo # MDEV-11608: pushdown of the predicate with cached null value
--echo #
CREATE TABLE t1 (c VARCHAR(3));
CREATE ALGORITHM=TEMPTABLE VIEW v1 AS SELECT * FROM t1;
INSERT INTO t1 VALUES ('foo'),('bar');
CREATE TABLE t2 (c VARCHAR(3));
INSERT INTO t2 VALUES ('foo'),('xyz');
SELECT * FROM v1 WHERE v1.c IN ( SELECT MIN(c) FROM t2 WHERE 0 );
EXPLAIN FORMAT=JSON
SELECT * FROM v1 WHERE v1.c IN ( SELECT MIN(c) FROM t2 WHERE 0 );
DROP VIEW v1;
DROP TABLE t1,t2;
CREATE TABLE t1 (d DECIMAL(10,2));
CREATE ALGORITHM=TEMPTABLE VIEW v1 AS SELECT * FROM t1;
INSERT INTO t1 VALUES (5.37),(1.1);
CREATE TABLE t2 (d DECIMAL(10,2));
INSERT INTO t2 VALUES ('1.1'),('2.23');
SELECT * FROM v1 WHERE v1.d IN ( SELECT MIN(d) FROM t2 WHERE 0 );
DROP VIEW v1;
DROP TABLE t1,t2;

19
sql/item.cc
View File

@ -9703,12 +9703,15 @@ my_decimal *Item_cache_decimal::val_decimal(my_decimal *val)
Item *Item_cache_decimal::convert_to_basic_const_item(THD *thd)
{
Item *new_item;
my_decimal decimal_value;
my_decimal *result= val_decimal(&decimal_value);
DBUG_ASSERT(value_cached || example != 0);
new_item= null_value ?
(Item*) new (thd->mem_root) Item_null(thd) :
(Item*) new (thd->mem_root) Item_decimal(thd, result);
if (null_value)
new_item= (Item*) new (thd->mem_root) Item_null(thd);
else
{
my_decimal decimal_value;
my_decimal *result= val_decimal(&decimal_value);
new_item= (Item*) new (thd->mem_root) Item_decimal(thd, result);
}
return new_item;
}
@ -9795,14 +9798,14 @@ bool Item_cache_row::allocate(THD *thd, uint num)
Item *Item_cache_str::convert_to_basic_const_item(THD *thd)
{
Item *new_item;
char buff[MAX_FIELD_WIDTH];
String tmp(buff, sizeof(buff), value->charset());
String *result= val_str(&tmp);
DBUG_ASSERT(value_cached || example != 0);
if (null_value)
new_item= (Item*) new (thd->mem_root) Item_null(thd);
else
{
char buff[MAX_FIELD_WIDTH];
String tmp(buff, sizeof(buff), value->charset());
String *result= val_str(&tmp);
uint length= result->length();
char *tmp_str= thd->strmake(result->ptr(), length);
new_item= new (thd->mem_root) Item_string(thd, tmp_str, length,