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MDEV-9690 concurrent queries with virtual columns crash in temporal code

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Item_func_le included Arg_comparator. Arg_comparator remembered
the current_thd during fix_fields and used that value during
execution to allocate Item_cache in get_datetime_value().
But for vcols fix_fields and val_int can happen in different threads.

Same bug for Item_func_in using in_datetime or cmp_item_datetime,
both also remembered current_thd at fix_fields() to use it later
for get_datetime_value().

As a fix, these objects no longer remember the current_thd,
and get_datetime_value() uses current_thd at run time. This
should not increase the number of current_thd calls much, as
Item_cache is created only once anyway.
This commit is contained in:
Sergei Golubchik 2017-01-14 14:56:01 +01:00
commit 67e2028161
4 changed files with 77 additions and 18 deletions
Download patch file Download diff file Expand all files Collapse all files

22
sql/item_cmpfunc.cc
View file

@ -777,7 +777,7 @@ int Arg_comparator::set_cmp_func(Item_result_field *owner_arg,
Item **a1, Item **a2,
Item_result type)
{
thd= current_thd;
THD *thd= current_thd;
owner= owner_arg;
set_null= set_null && owner_arg;
a= a1;
@ -846,7 +846,6 @@ Item** Arg_comparator::cache_converted_constant(THD *thd_arg, Item **value,
void Arg_comparator::set_datetime_cmp_func(Item_result_field *owner_arg,
Item **a1, Item **b1)
{
thd= current_thd;
owner= owner_arg;
a= a1;
b= b1;
@ -919,6 +918,9 @@ get_datetime_value(THD *thd, Item ***item_arg, Item **cache_arg,
if (cache_arg && item->const_item() &&
!(item->type() == Item::CACHE_ITEM && item->cmp_type() == TIME_RESULT))
{
if (!thd)
thd= current_thd;
Query_arena backup;
Query_arena *save_arena= thd->switch_to_arena_for_cached_items(&backup);
Item_cache_temporal *cache= new Item_cache_temporal(f_type);
@ -959,12 +961,12 @@ int Arg_comparator::compare_datetime()
owner->null_value= 1;
/* Get DATE/DATETIME/TIME value of the 'a' item. */
a_value= get_datetime_value(thd, &a, &a_cache, *b, &a_is_null);
a_value= get_datetime_value(0, &a, &a_cache, *b, &a_is_null);
if (a_is_null)
return -1;
/* Get DATE/DATETIME/TIME value of the 'b' item. */
b_value= get_datetime_value(thd, &b, &b_cache, *a, &b_is_null);
b_value= get_datetime_value(0, &b, &b_cache, *a, &b_is_null);
if (b_is_null)
return -1;
@ -982,10 +984,10 @@ int Arg_comparator::compare_e_datetime()
longlong a_value, b_value;
/* Get DATE/DATETIME/TIME value of the 'a' item. */
a_value= get_datetime_value(thd, &a, &a_cache, *b, &a_is_null);
a_value= get_datetime_value(0, &a, &a_cache, *b, &a_is_null);
/* Get DATE/DATETIME/TIME value of the 'b' item. */
b_value= get_datetime_value(thd, &b, &b_cache, *a, &b_is_null);
b_value= get_datetime_value(0, &b, &b_cache, *a, &b_is_null);
return a_is_null || b_is_null ? a_is_null == b_is_null
: a_value == b_value;
}
@ -3600,7 +3602,7 @@ void in_datetime::set(uint pos,Item *item)
bool is_null;
struct packed_longlong *buff= &((packed_longlong*) base)[pos];
buff->val= get_datetime_value(thd, &tmp_item, 0, warn_item, &is_null);
buff->val= get_datetime_value(0, &tmp_item, 0, warn_item, &is_null);
buff->unsigned_flag= 1L;
}
@ -3608,7 +3610,7 @@ uchar *in_datetime::get_value(Item *item)
{
bool is_null;
Item **tmp_item= lval_cache ? &lval_cache : &item;
tmp.val= get_datetime_value(thd, &tmp_item, &lval_cache, warn_item, &is_null);
tmp.val= get_datetime_value(0, &tmp_item, &lval_cache, warn_item, &is_null);
if (item->null_value)
return 0;
tmp.unsigned_flag= 1L;
@ -3852,7 +3854,7 @@ void cmp_item_datetime::store_value(Item *item)
{
bool is_null;
Item **tmp_item= lval_cache ? &lval_cache : &item;
value= get_datetime_value(thd, &tmp_item, &lval_cache, warn_item, &is_null);
value= get_datetime_value(0, &tmp_item, &lval_cache, warn_item, &is_null);
}
@ -3861,7 +3863,7 @@ int cmp_item_datetime::cmp(Item *arg)
bool is_null;
Item **tmp_item= &arg;
return value !=
get_datetime_value(thd, &tmp_item, 0, warn_item, &is_null);
get_datetime_value(0, &tmp_item, 0, warn_item, &is_null);
}

12
sql/item_cmpfunc.h
View file

@ -44,7 +44,6 @@ class Arg_comparator: public Sql_alloc
Arg_comparator *comparators; // used only for compare_row()
double precision;
/* Fields used in DATE/DATETIME comparison. */
THD *thd;
Item *a_cache, *b_cache; // Cached values of a and b items
// when one of arguments is NULL.
public:
@ -52,10 +51,10 @@ public:
/* Allow owner function to use string buffers. */
String value1, value2;
Arg_comparator(): set_null(TRUE), comparators(0), thd(0),
Arg_comparator(): set_null(TRUE), comparators(0),
a_cache(0), b_cache(0) {};
Arg_comparator(Item **a1, Item **a2): a(a1), b(a2), set_null(TRUE),
comparators(0), thd(0), a_cache(0), b_cache(0) {};
comparators(0), a_cache(0), b_cache(0) {};
int set_compare_func(Item_result_field *owner, Item_result type);
inline int set_compare_func(Item_result_field *owner_arg)
@ -944,15 +943,13 @@ public:
class in_datetime :public in_longlong
{
public:
THD *thd;
/* An item used to issue warnings. */
Item *warn_item;
/* Cache for the left item. */
Item *lval_cache;
in_datetime(Item *warn_item_arg, uint elements)
:in_longlong(elements), thd(current_thd), warn_item(warn_item_arg),
lval_cache(0) {};
:in_longlong(elements), warn_item(warn_item_arg), lval_cache(0) {};
void set(uint pos,Item *item);
uchar *get_value(Item *item);
Item* create_item()
@ -1112,14 +1109,13 @@ class cmp_item_datetime :public cmp_item
{
longlong value;
public:
THD *thd;
/* Item used for issuing warnings. */
Item *warn_item;
/* Cache for the left item. */
Item *lval_cache;
cmp_item_datetime(Item *warn_item_arg)
:thd(current_thd), warn_item(warn_item_arg), lval_cache(0) {}
: warn_item(warn_item_arg), lval_cache(0) {}
void store_value(Item *item);
int cmp(Item *arg);
int compare(cmp_item *ci);