#At file:///mnt/work/bzr_trees/34384-bug-5.1-bugteam/ based on revid:kristofer.pettersson@stripped
3147 Evgeny Potemkin 2009-10-21
Bug#34384: Slow down on constant conversion.
When values of different types are compared they're converted to a type that
allows correct comparison. This conversion is done for each comparison and
takes some time. When a constant is being compared it's possible to cache the
value after conversion to speedup comparison.
A test case isn't provided because all changes are internal and isn't visible
outside.
The behaviour of the Item_cache is changed to cache values on the first request
of cached value rather than at the moment of storing item to be cached.
A flag named value_caching is added to the Item_cache class. It's set to TRUE
when we need to start caching values when the store method is called.
Functions named init_cache and cache_value() are added to the Item_cache
class. Their purpose is to check state of the value_caching flag and store
item to be cached or cache its value accordingly.
Item_cache_xxx::store functions are changed to call init_caching prior to
store cached value.
Item_cache_xxx::val_xxx functions are changed to call cache_value prior to
return cached value if value_caching is true.
The Arg_comparator::set_cmp_func function is changed to cache a value being
compared if it's a constant and needs type conversion.
The Item_cache::get_cache function is overloaded to allow setting of the
cache type.
The cache_converted_constant function is added to the Arg_comparator class.
It checks whether a value can and should be cached and if so caches it.
@ sql/item.cc
Bug#34384: Slow down on constant conversion.
The Item_cache::get_cache function is overloaded to allow setting of the
cache type.
Item_cache_xxx::val_xxx functions are changed to call cache_value prior to return a value.
Item_cache_xxx::store functions are changed to call init_cache
prior to storing cached value.
@ sql/item.h
Bug#34384: Slow down on constant conversion.
A flag named value_caching is added to the Item_cache class. It's set to TRUE
when we need to start caching values when the store method is called.
Functions named init_cache and cache_value() are added to the Item_cache
class. Their purpose is to check state of the value_caching flag and store
item to be cached or cache its value accordingly.
@ sql/item_cmpfunc.cc
Bug#34384: Slow down on constant conversion.
A helper function cache_converted_constant is added to the Arg_comparator class.
It checks whether a given item can and should be cached and caches it if so.
@ sql/item_cmpfunc.h
Bug#34384: Slow down on constant conversion.
The cache_converted_constant function is added to the Arg_comparator class.
It checks whether a value can and should be cached and if so caches it.
@ sql/item_subselect.cc
Bug#34384: Slow down on constant conversion.
Force immediate caching of subselect result.
@ sql/item_xmlfunc.cc
Bug#34384: Slow down on constant conversion.
@ sql/sp_rcontext.cc
Bug#34384: Slow down on constant conversion.
modified:
sql/item.cc
sql/item.h
sql/item_cmpfunc.cc
sql/item_cmpfunc.h
sql/item_subselect.cc
sql/item_xmlfunc.cc
sql/sp_rcontext.cc
=== modified file 'sql/item.cc'
--- a/sql/item.cc 2009-09-29 02:23:38 +0000
+++ b/sql/item.cc 2009-10-21 11:57:23 +0000
@@ -6938,7 +6938,22 @@ int stored_field_cmp_to_item(Field *fiel
Item_cache* Item_cache::get_cache(const Item *item)
{
- switch (item->result_type()) {
+ return get_cache(item, item->result_type());
+}
+
+
+/**
+ Get a cache item of given type.
+
+ @param item value to be cached
+ @param type required type of cache
+
+ @return cache item
+*/
+
+Item_cache* Item_cache::get_cache(const Item *item, const Item_result type)
+{
+ switch (type) {
case INT_RESULT:
return new Item_cache_int();
case REAL_RESULT:
@@ -6967,9 +6982,10 @@ void Item_cache::print(String *str, enum
str->append(')');
}
-
void Item_cache_int::store(Item *item)
{
+ if (init_cache(item))
+ return;
value= item->val_int_result();
null_value= item->null_value;
unsigned_flag= item->unsigned_flag;
@@ -6978,6 +6994,8 @@ void Item_cache_int::store(Item *item)
void Item_cache_int::store(Item *item, longlong val_arg)
{
+ // An explicit values is given, save it.
+ value_caching= TRUE;
value= val_arg;
null_value= item->null_value;
unsigned_flag= item->unsigned_flag;
@@ -6987,6 +7005,8 @@ void Item_cache_int::store(Item *item, l
String *Item_cache_int::val_str(String *str)
{
DBUG_ASSERT(fixed == 1);
+ if (!value_caching)
+ cache_value();
str->set(value, default_charset());
return str;
}
@@ -6995,21 +7015,50 @@ String *Item_cache_int::val_str(String *
my_decimal *Item_cache_int::val_decimal(my_decimal *decimal_val)
{
DBUG_ASSERT(fixed == 1);
+ if (!value_caching)
+ cache_value();
int2my_decimal(E_DEC_FATAL_ERROR, value, unsigned_flag, decimal_val);
return decimal_val;
}
+double Item_cache_int::val_real()
+{
+ DBUG_ASSERT(fixed == 1);
+ if (!value_caching)
+ cache_value();
+ return (double) value;
+}
+
+longlong Item_cache_int::val_int()
+{
+ DBUG_ASSERT(fixed == 1);
+ if (!value_caching)
+ cache_value();
+ return value;
+}
void Item_cache_real::store(Item *item)
{
+ if (init_cache(item))
+ return;
value= item->val_result();
null_value= item->null_value;
}
+double Item_cache_real::val_real()
+{
+ DBUG_ASSERT(fixed == 1);
+ if (!value_caching)
+ cache_value();
+ return value;
+}
+
longlong Item_cache_real::val_int()
{
DBUG_ASSERT(fixed == 1);
+ if (!value_caching)
+ cache_value();
return (longlong) rint(value);
}
@@ -7017,6 +7066,8 @@ longlong Item_cache_real::val_int()
String* Item_cache_real::val_str(String *str)
{
DBUG_ASSERT(fixed == 1);
+ if (!value_caching)
+ cache_value();
str->set_real(value, decimals, default_charset());
return str;
}
@@ -7025,6 +7076,8 @@ String* Item_cache_real::val_str(String
my_decimal *Item_cache_real::val_decimal(my_decimal *decimal_val)
{
DBUG_ASSERT(fixed == 1);
+ if (!value_caching)
+ cache_value();
double2my_decimal(E_DEC_FATAL_ERROR, value, decimal_val);
return decimal_val;
}
@@ -7032,6 +7085,8 @@ my_decimal *Item_cache_real::val_decimal
void Item_cache_decimal::store(Item *item)
{
+ if (init_cache(item))
+ return;
my_decimal *val= item->val_decimal_result(&decimal_value);
if (!(null_value= item->null_value) && val != &decimal_value)
my_decimal2decimal(val, &decimal_value);
@@ -7041,6 +7096,8 @@ double Item_cache_decimal::val_real()
{
DBUG_ASSERT(fixed);
double res;
+ if (!value_caching)
+ cache_value();
my_decimal2double(E_DEC_FATAL_ERROR, &decimal_value, &res);
return res;
}
@@ -7049,6 +7106,8 @@ longlong Item_cache_decimal::val_int()
{
DBUG_ASSERT(fixed);
longlong res;
+ if (!value_caching)
+ cache_value();
my_decimal2int(E_DEC_FATAL_ERROR, &decimal_value, unsigned_flag, &res);
return res;
}
@@ -7056,6 +7115,8 @@ longlong Item_cache_decimal::val_int()
String* Item_cache_decimal::val_str(String *str)
{
DBUG_ASSERT(fixed);
+ if (!value_caching)
+ cache_value();
my_decimal_round(E_DEC_FATAL_ERROR, &decimal_value, decimals, FALSE,
&decimal_value);
my_decimal2string(E_DEC_FATAL_ERROR, &decimal_value, 0, 0, 0, str);
@@ -7065,12 +7126,16 @@ String* Item_cache_decimal::val_str(Stri
my_decimal *Item_cache_decimal::val_decimal(my_decimal *val)
{
DBUG_ASSERT(fixed);
+ if (!value_caching)
+ cache_value();
return &decimal_value;
}
void Item_cache_str::store(Item *item)
{
+ if (init_cache(item))
+ return;
value_buff.set(buffer, sizeof(buffer), item->collation.collation);
value= item->str_result(&value_buff);
if ((null_value= item->null_value))
@@ -7095,6 +7160,8 @@ double Item_cache_str::val_real()
DBUG_ASSERT(fixed == 1);
int err_not_used;
char *end_not_used;
+ if (!value_caching)
+ cache_value();
if (value)
return my_strntod(value->charset(), (char*) value->ptr(),
value->length(), &end_not_used, &err_not_used);
@@ -7106,6 +7173,8 @@ longlong Item_cache_str::val_int()
{
DBUG_ASSERT(fixed == 1);
int err;
+ if (!value_caching)
+ cache_value();
if (value)
return my_strntoll(value->charset(), value->ptr(),
value->length(), 10, (char**) 0, &err);
@@ -7113,9 +7182,21 @@ longlong Item_cache_str::val_int()
return (longlong)0;
}
+
+String* Item_cache_str::val_str(String *str)
+{
+ DBUG_ASSERT(fixed == 1);
+ if (!value_caching)
+ cache_value();
+ return value;
+}
+
+
my_decimal *Item_cache_str::val_decimal(my_decimal *decimal_val)
{
DBUG_ASSERT(fixed == 1);
+ if (!value_caching)
+ cache_value();
if (value)
string2my_decimal(E_DEC_FATAL_ERROR, value, decimal_val);
else
@@ -7126,6 +7207,8 @@ my_decimal *Item_cache_str::val_decimal(
int Item_cache_str::save_in_field(Field *field, bool no_conversions)
{
+ if (!value_caching)
+ cache_value();
int res= Item_cache::save_in_field(field, no_conversions);
return (is_varbinary && field->type() == MYSQL_TYPE_STRING &&
value->length() < field->field_length) ? 1 : res;
@@ -7160,10 +7243,13 @@ bool Item_cache_row::setup(Item * item)
void Item_cache_row::store(Item * item)
{
+ if (init_cache(item))
+ return;
null_value= 0;
item->bring_value();
for (uint i= 0; i < item_count; i++)
{
+ values[i]->value_caching= TRUE;
values[i]->store(item->element_index(i));
null_value|= values[i]->null_value;
}
=== modified file 'sql/item.h'
--- a/sql/item.h 2009-08-28 10:55:59 +0000
+++ b/sql/item.h 2009-10-21 11:57:23 +0000
@@ -1025,7 +1025,11 @@ class sp_head;
class Item_basic_constant :public Item
{
+ table_map used_table_map;
public:
+ Item_basic_constant(): Item(), used_table_map(0) {};
+ void set_used_tables(table_map map) { used_table_map= map; }
+ table_map used_tables() const { return used_table_map; }
/* to prevent drop fixed flag (no need parent cleanup call) */
void cleanup()
{
@@ -2891,14 +2895,25 @@ protected:
Field *cached_field;
enum enum_field_types cached_field_type;
public:
- Item_cache():
- example(0), used_table_map(0), cached_field(0), cached_field_type(MYSQL_TYPE_STRING)
+ /*
+ TRUE <=> cache value on the store() call.
+ In some cases it's not possible to get value of the item to be cached at
+ the moment of cached being created & initialized. This flag tells Item_cache
+ only to save the item to be cached without actually caching it.
+ On the first call of val_xxx function the value of the item will be
+ retrieved, cached and returned to the caller.
+ */
+ bool value_caching;
+ Item_cache():
+ example(0), used_table_map(0), cached_field(0), cached_field_type(MYSQL_TYPE_STRING),
+ value_caching(0)
{
fixed= 1;
null_value= 1;
}
Item_cache(enum_field_types field_type_arg):
- example(0), used_table_map(0), cached_field(0), cached_field_type(field_type_arg)
+ example(0), used_table_map(0), cached_field(0), cached_field_type(field_type_arg),
+ value_caching(0)
{
fixed= 1;
null_value= 1;
@@ -2922,6 +2937,7 @@ public:
enum Type type() const { return CACHE_ITEM; }
enum_field_types field_type() const { return cached_field_type; }
static Item_cache* get_cache(const Item *item);
+ static Item_cache* get_cache(const Item* item, const Item_result type);
table_map used_tables() const { return used_table_map; }
virtual void keep_array() {}
virtual void print(String *str, enum_query_type query_type);
@@ -2933,6 +2949,19 @@ public:
{
return this == item;
}
+ inline bool init_cache(Item *item)
+ {
+ if (value_caching)
+ return FALSE;
+ if (item)
+ example= item;
+ return TRUE;
+ }
+ inline void cache_value()
+ {
+ value_caching= TRUE;
+ store(example);
+ }
};
@@ -2941,14 +2970,15 @@ class Item_cache_int: public Item_cache
protected:
longlong value;
public:
- Item_cache_int(): Item_cache(), value(0) {}
+ Item_cache_int(): Item_cache(),
+ value(0) {}
Item_cache_int(enum_field_types field_type_arg):
Item_cache(field_type_arg), value(0) {}
void store(Item *item);
void store(Item *item, longlong val_arg);
- double val_real() { DBUG_ASSERT(fixed == 1); return (double) value; }
- longlong val_int() { DBUG_ASSERT(fixed == 1); return value; }
+ double val_real();
+ longlong val_int();
String* val_str(String *str);
my_decimal *val_decimal(my_decimal *);
enum Item_result result_type() const { return INT_RESULT; }
@@ -2960,10 +2990,11 @@ class Item_cache_real: public Item_cache
{
double value;
public:
- Item_cache_real(): Item_cache(), value(0) {}
+ Item_cache_real(): Item_cache(),
+ value(0) {}
void store(Item *item);
- double val_real() { DBUG_ASSERT(fixed == 1); return value; }
+ double val_real();
longlong val_int();
String* val_str(String *str);
my_decimal *val_decimal(my_decimal *);
@@ -3004,7 +3035,7 @@ public:
void store(Item *item);
double val_real();
longlong val_int();
- String* val_str(String *) { DBUG_ASSERT(fixed == 1); return value; }
+ String* val_str(String *);
my_decimal *val_decimal(my_decimal *);
enum Item_result result_type() const { return STRING_RESULT; }
CHARSET_INFO *charset() const { return value->charset(); };
@@ -3018,7 +3049,8 @@ class Item_cache_row: public Item_cache
bool save_array;
public:
Item_cache_row()
- :Item_cache(), values(0), item_count(2), save_array(0) {}
+ :Item_cache(), values(0), item_count(2),
+ save_array(0) {}
/*
'allocate' used only in row transformer, to preallocate space for row
=== modified file 'sql/item_cmpfunc.cc'
--- a/sql/item_cmpfunc.cc 2009-10-05 05:27:36 +0000
+++ b/sql/item_cmpfunc.cc 2009-10-21 11:57:23 +0000
@@ -855,13 +855,13 @@ int Arg_comparator::set_cmp_func(Item_bo
{
enum enum_date_cmp_type cmp_type;
ulonglong const_value= (ulonglong)-1;
+ thd= current_thd;
+ owner= owner_arg;
a= a1;
b= a2;
if ((cmp_type= can_compare_as_dates(*a, *b, &const_value)))
{
- thd= current_thd;
- owner= owner_arg;
a_type= (*a)->field_type();
b_type= (*b)->field_type();
a_cache= 0;
@@ -894,8 +894,6 @@ int Arg_comparator::set_cmp_func(Item_bo
(*b)->field_type() == MYSQL_TYPE_TIME)
{
/* Compare TIME values as integers. */
- thd= current_thd;
- owner= owner_arg;
a_cache= 0;
b_cache= 0;
is_nulls_eq= test(owner && owner->functype() == Item_func::EQUAL_FUNC);
@@ -914,10 +912,47 @@ int Arg_comparator::set_cmp_func(Item_bo
return 1;
}
+ a= cache_converted_constant(a, &a_cache, type);
+ b= cache_converted_constant(b, &b_cache, type);
return set_compare_func(owner_arg, type);
}
+/**
+ Convert and cache a constant.
+
+ @param value [in] An item to cache
+ @param cache_item [out] Placeholder for the cache item
+ @param type [in] Comparison type
+
+ @details
+ When given item is a constant and its type differs from comparison type
+ then cache its value to avoid type conversion of this constant on each
+ evaluation. In this case the value is cached and the reference to the cache
+ is returned.
+ Original value is returned otherwise.
+
+ @return cache item or original value.
+*/
+
+Item** Arg_comparator::cache_converted_constant(Item **value,
+ Item **cache_item,
+ Item_result type)
+{
+ /* Don't need cache if doing context analysis only. */
+ if (!current_thd->is_context_analysis_only() &&
+ owner->functype() != Item_func::LIKE_FUNC &&
+ (*value)->const_item() && type != (*value)->result_type())
+ {
+ Item_cache *cache= Item_cache::get_cache(*value, type);
+ cache->store(*value);
+ *cache_item= cache;
+ return cache_item;
+ }
+ return value;
+}
+
+
void Arg_comparator::set_datetime_cmp_func(Item **a1, Item **b1)
{
thd= current_thd;
@@ -1556,6 +1591,7 @@ longlong Item_in_optimizer::val_int()
bool tmp;
DBUG_ASSERT(fixed == 1);
cache->store(args[0]);
+ cache->cache_value();
if (cache->null_value)
{
=== modified file 'sql/item_cmpfunc.h'
--- a/sql/item_cmpfunc.h 2008-12-12 11:13:11 +0000
+++ b/sql/item_cmpfunc.h 2009-10-21 11:57:23 +0000
@@ -94,6 +94,8 @@ public:
ulonglong *const_val_arg);
void set_datetime_cmp_func(Item **a1, Item **b1);
+ Item** cache_converted_constant(Item **value, Item **cache,
+ Item_result type);
static arg_cmp_func comparator_matrix [5][2];
friend class Item_func;
=== modified file 'sql/item_subselect.cc'
--- a/sql/item_subselect.cc 2009-09-04 08:14:54 +0000
+++ b/sql/item_subselect.cc 2009-10-21 11:57:23 +0000
@@ -1826,6 +1826,7 @@ void subselect_engine::set_row(List<Item
if (!(row[i]= Item_cache::get_cache(sel_item)))
return;
row[i]->setup(sel_item);
+ row[i]->value_caching= TRUE;
}
if (item_list.elements > 1)
res_type= ROW_RESULT;
=== modified file 'sql/item_xmlfunc.cc'
--- a/sql/item_xmlfunc.cc 2009-09-23 13:21:29 +0000
+++ b/sql/item_xmlfunc.cc 2009-10-21 11:57:23 +0000
@@ -941,14 +941,16 @@ static Item *create_comparator(MY_XPATH
in a loop through all of the nodes in the node set.
*/
- Item *fake= new Item_string("", 0, xpath->cs);
+ Item_string *fake= new Item_string("", 0, xpath->cs);
+ /* Don't cache fake because its value will be changed during comparison.*/
+ fake->set_used_tables(RAND_TABLE_BIT);
Item_nodeset_func *nodeset;
Item *scalar, *comp;
if (a->type() == Item::XPATH_NODESET)
{
nodeset= (Item_nodeset_func*) a;
scalar= b;
- comp= eq_func(oper, fake, scalar);
+ comp= eq_func(oper, (Item*)fake, scalar);
}
else
{
=== modified file 'sql/sp_rcontext.cc'
--- a/sql/sp_rcontext.cc 2008-01-23 22:36:57 +0000
+++ b/sql/sp_rcontext.cc 2009-10-21 11:57:23 +0000
@@ -616,6 +616,7 @@ sp_rcontext::set_case_expr(THD *thd, int
create_case_expr_holder(thd, case_expr_item);
}
+ m_case_expr_holders[case_expr_id]->value_caching= TRUE;
m_case_expr_holders[case_expr_id]->store(case_expr_item);
return FALSE;
Attachment: [text/bzr-bundle] bzr/epotemkin@mysql.com-20091021115723-k8mpxt2eoc72f0uo.bundle
