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CASE optimization

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unknown 2003-07-18 13:11:47 +05:00
parent a975548b53
commit f4e07b861e
1 changed files with 30 additions and 28 deletions
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58
sql/item_cmpfunc.cc
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@ -863,58 +863,60 @@ Item *Item_func_case::find_item(String *str)
String *first_expr_str,*tmp;
longlong first_expr_int;
double first_expr_real;
bool int_used, real_used,str_used;
int_used=real_used=str_used=0;
/* These will be initialized later */
LINT_INIT(first_expr_str);
LINT_INIT(first_expr_int);
LINT_INIT(first_expr_real);
if (first_expr_num != -1)
{
switch (cmp_type)
{
case STRING_RESULT:
// We can't use 'str' here as this may be overwritten
if (!(first_expr_str= args[first_expr_num]->val_str(&str_value)))
return else_expr_num != -1 ? args[else_expr_num] : 0; // Impossible
break;
case INT_RESULT:
first_expr_int= args[first_expr_num]->val_int();
if (args[first_expr_num]->null_value)
return else_expr_num != -1 ? args[else_expr_num] : 0;
break;
case REAL_RESULT:
first_expr_real= args[first_expr_num]->val();
if (args[first_expr_num]->null_value)
return else_expr_num != -1 ? args[else_expr_num] : 0;
break;
case ROW_RESULT:
default:
// This case should never be choosen
DBUG_ASSERT(0);
break;
}
}
// Compare every WHEN argument with it and return the first match
for (uint i=0 ; i < ncases ; i+=2)
{
if (first_expr_num == -1)
{
// No expression between CASE and first WHEN
// No expression between CASE and the first WHEN
if (args[i]->val_int())
return args[i+1];
continue;
}
switch (args[i]->result_type()) {
switch (cmp_type) {
case STRING_RESULT:
if (!str_used)
{
str_used=1;
// We can't use 'str' here as this may be overwritten
if (!(first_expr_str= args[first_expr_num]->val_str(&str_value)))
return else_expr_num != -1 ? args[else_expr_num] : 0; // Impossible
}
if ((tmp=args[i]->val_str(str))) // If not null
{
if (sortcmp(tmp,first_expr_str,cmp_collation.collation)==0)
return args[i+1];
}
break;
case INT_RESULT:
if (!int_used)
{
int_used=1;
first_expr_int= args[first_expr_num]->val_int();
if (args[first_expr_num]->null_value)
return else_expr_num != -1 ? args[else_expr_num] : 0;
}
if (args[i]->val_int()==first_expr_int && !args[i]->null_value)
return args[i+1];
break;
case REAL_RESULT:
if (!real_used)
{
real_used=1;
first_expr_real= args[first_expr_num]->val();
if (args[first_expr_num]->null_value)
return else_expr_num != -1 ? args[else_expr_num] : 0;
}
if (args[i]->val()==first_expr_real && !args[i]->null_value)
return args[i+1];
break;