#At file:///work/bzrroot/34384-bug-next/ based on revid:epotemkin@stripped
2864 Evgeny Potemkin 2009-09-19
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.
A flag named uncacheable is added to the Item class. It denies caching of the
item.
A flag named late_caching is added to the Item_cache class. It's set to TRUE
when we need to postpone caching till the first use of cached value.
A function named check_late_caching is added to the Item_cache flag. Its
purpose is to check state of the late_caching flag and cache value accordingly.
Item_cache_xxx::val_xxx functions are changed to call it prior to return
cached value.
The Arg_comparator::set_cmp_func function is changed to cache a value being
compared if it's a constant and needs type conversion.
Now the Item_func_like::fix_fields function denies caching arguments of the LIKE
function.
The Item_cache::get_cache function is overloaded to allow setting of the
late_caching flag and cache type.
@ mysql-test/r/range.result
Adjusted a test case after fix for the bug#34384.
@ sql/item.cc
Bug#34384: Slow down on constant conversion.
A flag named uncacheable is added to the Item class. It denies caching of the
item.
The Item_cache::get_cache function is overloaded to allow setting of the
late_caching flag and cache type.
Item_cache_xxx::val_xxx functions are changed to call it prior to return
cached value.
@ sql/item.h
Bug#34384: Slow down on constant conversion.
A function named check_late_caching is added to the Item_cache flag. Its
purpose is to check state of the late_caching flag and cache value accordingly.
The Item_cache::get_cache function is overloaded to allow setting of the
late_caching flag and cache type.
@ sql/item_cmpfunc.cc
Bug#34384: Slow down on constant conversion.
The Arg_comparator::set_cmp_func function is changed to cache a value being
compared if it's a constant and needs type conversion.
@ sql/item_cmpfunc.h
Bug#34384: Slow down on constant conversion.
@ sql/item_xmlfunc.cc
Bug#34384: Slow down on constant conversion.
modified:
mysql-test/r/range.result
sql/item.cc
sql/item.h
sql/item_cmpfunc.cc
sql/item_cmpfunc.h
sql/item_xmlfunc.cc
=== modified file 'mysql-test/r/range.result'
--- a/mysql-test/r/range.result 2008-06-10 22:27:52 +0000
+++ b/mysql-test/r/range.result 2009-09-19 17:55:58 +0000
@@ -1230,8 +1230,6 @@ c1
Warnings:
Warning 1366 Incorrect decimal value: 'A' for column 'c1' at row 1
Warning 1292 Truncated incorrect DOUBLE value: 'A'
-Warning 1292 Truncated incorrect DOUBLE value: 'A'
-Warning 1292 Truncated incorrect DOUBLE value: 'A'
DROP TABLE t1;
create table t1 (a int,b int,key (b),key (a),key (b,a));
insert into t1(a,b) values (1,2),(3,4),(5,6),(7,8);
=== modified file 'sql/item.cc'
--- a/sql/item.cc 2009-07-23 12:21:41 +0000
+++ b/sql/item.cc 2009-09-19 17:55:58 +0000
@@ -376,7 +376,8 @@ int Item::save_str_value_in_field(Field
Item::Item():
is_expensive_cache(-1), rsize(0), name(0), orig_name(0), name_length(0),
fixed(0), is_autogenerated_name(TRUE),
- collation(&my_charset_bin, DERIVATION_COERCIBLE)
+ collation(&my_charset_bin, DERIVATION_COERCIBLE),
+ uncacheable(0)
{
marker= 0;
maybe_null=null_value=with_sum_func=unsigned_flag=0;
@@ -7136,17 +7137,22 @@ bool field_is_equal_to_item(Field *field
Item_cache* Item_cache::get_cache(const Item *item)
{
- switch (item->result_type()) {
+ return get_cache(item->result_type(), item, FALSE);
+}
+
+Item_cache* Item_cache::get_cache(const Item_result type, const Item *item, bool late_caching)
+{
+ switch (type) {
case INT_RESULT:
- return new Item_cache_int();
+ return new Item_cache_int(late_caching);
case REAL_RESULT:
- return new Item_cache_real();
+ return new Item_cache_real(late_caching);
case DECIMAL_RESULT:
- return new Item_cache_decimal();
+ return new Item_cache_decimal(late_caching);
case STRING_RESULT:
- return new Item_cache_str(item);
+ return new Item_cache_str(item,late_caching);
case ROW_RESULT:
- return new Item_cache_row();
+ return new Item_cache_row(late_caching);
default:
// should never be in real life
DBUG_ASSERT(0);
@@ -7168,6 +7174,8 @@ void Item_cache::print(String *str, enum
void Item_cache_int::store(Item *item)
{
+ if (check_late_caching(item))
+ return;
value= item->val_int_result();
null_value= item->null_value;
unsigned_flag= item->unsigned_flag;
@@ -7176,6 +7184,8 @@ void Item_cache_int::store(Item *item)
void Item_cache_int::store(Item *item, longlong val_arg)
{
+ if (check_late_caching(item))
+ return;
value= val_arg;
null_value= item->null_value;
unsigned_flag= item->unsigned_flag;
@@ -7185,6 +7195,7 @@ void Item_cache_int::store(Item *item, l
String *Item_cache_int::val_str(String *str)
{
DBUG_ASSERT(fixed == 1);
+ check_late_caching(NULL);
str->set(value, default_charset());
return str;
}
@@ -7193,6 +7204,7 @@ String *Item_cache_int::val_str(String *
my_decimal *Item_cache_int::val_decimal(my_decimal *decimal_val)
{
DBUG_ASSERT(fixed == 1);
+ check_late_caching(NULL);
int2my_decimal(E_DEC_FATAL_ERROR, value, unsigned_flag, decimal_val);
return decimal_val;
}
@@ -7200,6 +7212,8 @@ my_decimal *Item_cache_int::val_decimal(
void Item_cache_real::store(Item *item)
{
+ if (check_late_caching(item))
+ return;
value= item->val_result();
null_value= item->null_value;
}
@@ -7208,6 +7222,7 @@ void Item_cache_real::store(Item *item)
longlong Item_cache_real::val_int()
{
DBUG_ASSERT(fixed == 1);
+ check_late_caching(NULL);
return (longlong) rint(value);
}
@@ -7215,6 +7230,7 @@ longlong Item_cache_real::val_int()
String* Item_cache_real::val_str(String *str)
{
DBUG_ASSERT(fixed == 1);
+ check_late_caching(NULL);
str->set_real(value, decimals, default_charset());
return str;
}
@@ -7223,6 +7239,7 @@ String* Item_cache_real::val_str(String
my_decimal *Item_cache_real::val_decimal(my_decimal *decimal_val)
{
DBUG_ASSERT(fixed == 1);
+ check_late_caching(NULL);
double2my_decimal(E_DEC_FATAL_ERROR, value, decimal_val);
return decimal_val;
}
@@ -7230,6 +7247,8 @@ my_decimal *Item_cache_real::val_decimal
void Item_cache_decimal::store(Item *item)
{
+ if (check_late_caching(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);
@@ -7239,6 +7258,7 @@ double Item_cache_decimal::val_real()
{
DBUG_ASSERT(fixed);
double res;
+ check_late_caching(NULL);
my_decimal2double(E_DEC_FATAL_ERROR, &decimal_value, &res);
return res;
}
@@ -7247,6 +7267,7 @@ longlong Item_cache_decimal::val_int()
{
DBUG_ASSERT(fixed);
longlong res;
+ check_late_caching(NULL);
my_decimal2int(E_DEC_FATAL_ERROR, &decimal_value, unsigned_flag, &res);
return res;
}
@@ -7254,6 +7275,7 @@ longlong Item_cache_decimal::val_int()
String* Item_cache_decimal::val_str(String *str)
{
DBUG_ASSERT(fixed);
+ check_late_caching(NULL);
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);
@@ -7263,12 +7285,15 @@ String* Item_cache_decimal::val_str(Stri
my_decimal *Item_cache_decimal::val_decimal(my_decimal *val)
{
DBUG_ASSERT(fixed);
+ check_late_caching(NULL);
return &decimal_value;
}
void Item_cache_str::store(Item *item)
{
+ if (check_late_caching(item))
+ return;
value_buff.set(buffer, sizeof(buffer), item->collation.collation);
value= item->str_result(&value_buff);
if ((null_value= item->null_value))
@@ -7293,6 +7318,7 @@ double Item_cache_str::val_real()
DBUG_ASSERT(fixed == 1);
int err_not_used;
char *end_not_used;
+ check_late_caching(NULL);
if (value)
return my_strntod(value->charset(), (char*) value->ptr(),
value->length(), &end_not_used, &err_not_used);
@@ -7304,6 +7330,7 @@ longlong Item_cache_str::val_int()
{
DBUG_ASSERT(fixed == 1);
int err;
+ check_late_caching(NULL);
if (value)
return my_strntoll(value->charset(), value->ptr(),
value->length(), 10, (char**) 0, &err);
@@ -7314,6 +7341,7 @@ longlong Item_cache_str::val_int()
my_decimal *Item_cache_str::val_decimal(my_decimal *decimal_val)
{
DBUG_ASSERT(fixed == 1);
+ check_late_caching(NULL);
if (value)
string2my_decimal(E_DEC_FATAL_ERROR, value, decimal_val);
else
@@ -7324,6 +7352,7 @@ my_decimal *Item_cache_str::val_decimal(
int Item_cache_str::save_in_field(Field *field, bool no_conversions)
{
+ check_late_caching(NULL);
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;
@@ -7341,6 +7370,8 @@ bool Item_cache_row::allocate(uint num)
bool Item_cache_row::setup(Item * item)
{
+ if (check_late_caching(item))
+ return FALSE;
example= item;
if (!values && allocate(item->cols()))
return 1;
@@ -7358,6 +7389,8 @@ bool Item_cache_row::setup(Item * item)
void Item_cache_row::store(Item * item)
{
+ if (check_late_caching(item))
+ return;
null_value= 0;
item->bring_value();
for (uint i= 0; i < item_count; i++)
=== modified file 'sql/item.h'
--- a/sql/item.h 2009-06-24 17:00:59 +0000
+++ b/sql/item.h 2009-09-19 17:55:58 +0000
@@ -532,6 +532,7 @@ public:
of its arguments is or contains a
subselect. Computed by fix_fields. */
Item_result cmp_context; /* Comparison context */
+ bool uncacheable;
// alloc & destruct is done as start of select using sql_alloc
Item();
/*
@@ -2995,14 +2996,24 @@ protected:
Field *cached_field;
enum enum_field_types cached_field_type;
public:
+ bool late_caching;
Item_cache():
- example(0), used_table_map(0), cached_field(0), cached_field_type(MYSQL_TYPE_STRING)
+ example(0), used_table_map(0), cached_field(0), cached_field_type(MYSQL_TYPE_STRING),
+ late_caching(0)
+ {
+ fixed= 1;
+ null_value= 1;
+ }
+ Item_cache(bool late_caching_arg):
+ example(0), used_table_map(0), cached_field(0), cached_field_type(MYSQL_TYPE_STRING),
+ late_caching(late_caching_arg)
{
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),
+ late_caching(0)
{
fixed= 1;
null_value= 1;
@@ -3026,6 +3037,8 @@ 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_result type, const Item* item,
+ bool late_caching);
table_map used_tables() const { return used_table_map; }
virtual void keep_array() {}
virtual void print(String *str, enum_query_type query_type);
@@ -3037,6 +3050,18 @@ public:
{
return this == item;
}
+ inline bool check_late_caching(Item *item)
+ {
+ if (!late_caching)
+ return FALSE;
+ if (item)
+ example= item;
+ else {
+ late_caching= FALSE;
+ store(example);
+ }
+ return TRUE;
+ }
};
@@ -3046,13 +3071,24 @@ protected:
longlong value;
public:
Item_cache_int(): Item_cache(), value(0) {}
+ Item_cache_int(bool late_caching_arg): Item_cache(late_caching_arg), 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()
+ {
+ DBUG_ASSERT(fixed == 1);
+ check_late_caching(NULL);
+ return (double) value;
+ }
+ longlong val_int()
+ {
+ DBUG_ASSERT(fixed == 1);
+ check_late_caching(NULL);
+ return value;
+ }
String* val_str(String *str);
my_decimal *val_decimal(my_decimal *);
enum Item_result result_type() const { return INT_RESULT; }
@@ -3065,9 +3101,15 @@ class Item_cache_real: public Item_cache
double value;
public:
Item_cache_real(): Item_cache(), value(0) {}
+ Item_cache_real(bool late_caching_arg): Item_cache(late_caching_arg), value(0) {}
void store(Item *item);
- double val_real() { DBUG_ASSERT(fixed == 1); return value; }
+ double val_real()
+ {
+ DBUG_ASSERT(fixed == 1);
+ check_late_caching(NULL);
+ return value;
+ }
longlong val_int();
String* val_str(String *str);
my_decimal *val_decimal(my_decimal *);
@@ -3081,6 +3123,7 @@ protected:
my_decimal decimal_value;
public:
Item_cache_decimal(): Item_cache() {}
+ Item_cache_decimal(bool late_caching_arg): Item_cache(late_caching_arg) {}
void store(Item *item);
double val_real();
@@ -3105,10 +3148,22 @@ public:
MYSQL_TYPE_VARCHAR &&
!((const Item_field *) item)->field->has_charset())
{}
+ Item_cache_str(const Item *item, bool late_caching_arg) :
+ Item_cache(late_caching_arg), value(0),
+ is_varbinary(item->type() == FIELD_ITEM &&
+ ((const Item_field *) item)->field->type() ==
+ MYSQL_TYPE_VARCHAR &&
+ !((const Item_field *) item)->field->has_charset())
+ {}
void store(Item *item);
double val_real();
longlong val_int();
- String* val_str(String *) { DBUG_ASSERT(fixed == 1); return value; }
+ String* val_str(String *)
+ {
+ DBUG_ASSERT(fixed == 1);
+ check_late_caching(NULL);
+ return value;
+ }
my_decimal *val_decimal(my_decimal *);
enum Item_result result_type() const { return STRING_RESULT; }
CHARSET_INFO *charset() const { return value->charset(); };
@@ -3123,6 +3178,9 @@ class Item_cache_row: public Item_cache
public:
Item_cache_row()
:Item_cache(), values(0), item_count(2), save_array(0) {}
+ Item_cache_row(bool late_caching_arg)
+ :Item_cache(late_caching_arg), 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 2009-07-03 10:39:01 +0000
+++ b/sql/item_cmpfunc.cc 2009-09-19 17:55:58 +0000
@@ -524,6 +524,13 @@ void Item_bool_func2::fix_length_and_dec
set_cmp_func();
}
+void Item_bool_func2::set_cmp_func()
+{
+ /* Don't need cache for context analysis. */
+ if (!current_thd->is_context_analysis_only())
+ tmp_arg[0]->uncacheable= tmp_arg[1]->uncacheable= TRUE;
+ cmp.set_cmp_func(this, tmp_arg, tmp_arg+1);
+}
int Arg_comparator::set_compare_func(Item_bool_func2 *item, Item_result type)
{
@@ -847,6 +854,7 @@ int Arg_comparator::set_cmp_func(Item_bo
Item_result type)
{
ulonglong const_value= (ulonglong)-1;
+ Item_cache *cache;
a= a1;
b= a2;
@@ -906,6 +914,28 @@ int Arg_comparator::set_cmp_func(Item_bo
return 1;
}
+ {
+ /*
+ When one of items being compared is a constant and its type
+ differs from comparison type then cache such item to avoid
+ type conversion of this constant on each evaluation.
+ */
+ if ((*a)->const_item() && !(*a)->uncacheable &&
+ type != (*a)->result_type())
+ {
+ cache= Item_cache::get_cache(type, *a, TRUE);
+ cache->store(*a);
+ a_cache= cache;
+ a= (Item **)&a_cache;
+ } else if ((*b)->const_item() && !(*b)->uncacheable &&
+ type != (*b)->result_type())
+ {
+ cache= Item_cache::get_cache(type, *b, TRUE);
+ cache->store(*b);
+ b_cache= cache;
+ b= (Item **)&b_cache;
+ }
+ }
return set_compare_func(owner_arg, type);
}
@@ -4465,6 +4495,11 @@ Item_func::optimize_type Item_func_like:
bool Item_func_like::fix_fields(THD *thd, Item **ref)
{
DBUG_ASSERT(fixed == 0);
+
+ /* LIKE doesn't compare arguments directly, thus no reason to cache them. */
+ for (int i= 0; i < arg_count; i++)
+ args[i]->uncacheable= TRUE;
+
if (Item_bool_func2::fix_fields(thd, ref) ||
escape_item->fix_fields(thd, &escape_item))
return TRUE;
=== modified file 'sql/item_cmpfunc.h'
--- a/sql/item_cmpfunc.h 2009-06-22 09:36:50 +0000
+++ b/sql/item_cmpfunc.h 2009-09-19 17:55:58 +0000
@@ -335,10 +335,7 @@ public:
Item_bool_func2(Item *a,Item *b)
:Item_int_func(a,b), cmp(tmp_arg, tmp_arg+1), abort_on_null(FALSE) {}
void fix_length_and_dec();
- void set_cmp_func()
- {
- cmp.set_cmp_func(this, tmp_arg, tmp_arg+1);
- }
+ void set_cmp_func();
optimize_type select_optimize() const { return OPTIMIZE_OP; }
virtual enum Functype rev_functype() const { return UNKNOWN_FUNC; }
bool have_rev_func() const { return rev_functype() != UNKNOWN_FUNC; }
=== modified file 'sql/item_xmlfunc.cc'
--- a/sql/item_xmlfunc.cc 2009-07-28 14:16:37 +0000
+++ b/sql/item_xmlfunc.cc 2009-09-19 17:55:58 +0000
@@ -952,6 +952,8 @@ static Item *create_comparator(MY_XPATH
*/
Item *fake= new Item_string("", 0, xpath->cs);
+ /* Don't cache fake because its value will be changed during comparison.*/
+ fake->uncacheable= TRUE;
Item_nodeset_func *nodeset;
Item *scalar, *comp;
if (a->type() == Item::XPATH_NODESET)
Attachment: [text/bzr-bundle] bzr/epotemkin@mysql.com-20090919175558-eqekzibs1e9bjamh.bundle
