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/*
Copyright (c) 2000, 2010, Oracle and/or its affiliates.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
/**
@file
@brief
Buffers to save and compare item values
*/
#include "sql_priv.h"
/*
It is necessary to include set_var.h instead of item.h because there
are dependencies on include order for set_var.h and item.h. This
will be resolved later.
*/
#include "sql_class.h" // THD
#include "set_var.h" // Cached_item, Cached_item_field, ...
/**
Create right type of Cached_item for an item.
*/
Cached_item *new_Cached_item(THD *thd, Item *item, bool pass_through_ref)
{
if (pass_through_ref && item->real_item()->type() == Item::FIELD_ITEM &&
!(((Item_field *) (item->real_item()))->field->flags & BLOB_FLAG))
{
Item_field *real_item= (Item_field *) item->real_item();
Field *cached_field= real_item->field;
return new Cached_item_field(cached_field);
}
switch (item->result_type()) {
case STRING_RESULT:
return new Cached_item_str(thd, (Item_field *) item);
case INT_RESULT:
return new Cached_item_int((Item_field *) item);
case REAL_RESULT:
return new Cached_item_real(item);
case DECIMAL_RESULT:
return new Cached_item_decimal(item);
case ROW_RESULT:
default:
DBUG_ASSERT(0);
return 0;
}
}
Cached_item::~Cached_item() {}
/**
Compare with old value and replace value with new value.
@return
Return true if values have changed
*/
Cached_item_str::Cached_item_str(THD *thd, Item *arg)
:item(arg),
value_max_length(min(arg->max_length, thd->variables.max_sort_length)),
value(value_max_length)
{}
bool Cached_item_str::cmp(void)
{
String *res;
bool tmp;
if ((res=item->val_str(&tmp_value)))
res->length(min(res->length(), value_max_length));
if (null_value != item->null_value)
{
if ((null_value= item->null_value))
return TRUE; // New value was null
tmp=TRUE;
}
else if (null_value)
return 0; // new and old value was null
else
tmp= sortcmp(&value,res,item->collation.collation) != 0;
if (tmp)
value.copy(*res); // Remember for next cmp
return tmp;
}
Cached_item_str::~Cached_item_str()
{
item=0; // Safety
}
bool Cached_item_real::cmp(void)
{
double nr= item->val_real();
if (null_value != item->null_value || nr != value)
{
null_value= item->null_value;
value=nr;
return TRUE;
}
return FALSE;
}
bool Cached_item_int::cmp(void)
{
longlong nr=item->val_int();
if (null_value != item->null_value || nr != value)
{
null_value= item->null_value;
value=nr;
return TRUE;
}
return FALSE;
}
bool Cached_item_field::cmp(void)
{
bool tmp= FALSE; // Value is identical
/* Note that field can't be a blob here ! */
if (null_value != field->is_null())
{
null_value= !null_value;
tmp= TRUE; // Value has changed
}
/*
If value is not null and value changed (from null to not null or
becasue of value change), then copy the new value to buffer.
*/
if (! null_value && (tmp || (tmp= (field->cmp(buff) != 0))))
field->get_image(buff,length,field->charset());
return tmp;
}
Cached_item_decimal::Cached_item_decimal(Item *it)
:item(it)
{
my_decimal_set_zero(&value);
}
bool Cached_item_decimal::cmp()
{
my_decimal tmp;
my_decimal *ptmp= item->val_decimal(&tmp);
if (null_value != item->null_value ||
(!item->null_value && my_decimal_cmp(&value, ptmp)))
{
null_value= item->null_value;
/* Save only not null values */
if (!null_value)
{
my_decimal2decimal(ptmp, &value);
return TRUE;
}
return FALSE;
}
return FALSE;
}
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