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Allow to convert to non-Unicode charset when mixing a string

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constant with a column. The string is converted into the column
character set. It conversion doesn't lose data, then operation
is possible. Otherwise, give an error, as it was earlier.
This commit is contained in:
bar@mysql.com
2004-10-29 16:00:03 +05:00
parent 8d620b9344
commit ea49a5181a
7 changed files with 187 additions and 74 deletions
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118
sql/item_cmpfunc.cc
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@@ -174,62 +174,87 @@ void Item_bool_func2::fix_length_and_dec()
return;
/*
We allow to convert to Unicode character sets in some cases.
We allow to apply automatic character set conversion in some cases.
The conditions when conversion is possible are:
- arguments A and B have different charsets
- A wins according to coercibility rules
- character set of A is superset for character set of B
(i.e. a column is stronger than a string constant,
an explicit COLLATE clause is stronger than a column)
- character set of A is either superset for character set of B,
or B is a string constant which can be converted into the
character set of A without data loss.
If all of the above is true, then it's possible to convert
B into the character set of A, and then compare according
to the collation of A.
*/
if (args[0] && args[1])
{
uint strong= 0;
uint weak= 0;
uint32 dummy_offset;
DTCollation coll;
uint32 dummy_offset;
DTCollation coll;
if (args[0]->result_type() == STRING_RESULT &&
args[1]->result_type() == STRING_RESULT &&
String::needs_conversion(0, args[0]->collation.collation,
args[1]->collation.collation,
&dummy_offset) &&
!coll.set(args[0]->collation, args[1]->collation, TRUE))
if (args[0]->result_type() == STRING_RESULT &&
args[1]->result_type() == STRING_RESULT &&
String::needs_conversion(0, args[0]->collation.collation,
args[1]->collation.collation,
&dummy_offset) &&
!coll.set(args[0]->collation, args[1]->collation,
MY_COLL_ALLOW_SUPERSET_CONV |
MY_COLL_ALLOW_COERCIBLE_CONV))
{
Item* conv= 0;
Item_arena *arena= thd->current_arena, backup;
uint strong= coll.strong;
uint weak= strong ? 0 : 1;
/*
In case we're in statement prepare, create conversion item
in its memory: it will be reused on each execute.
*/
if (arena->is_stmt_prepare())
thd->set_n_backup_item_arena(arena, &backup);
if (args[weak]->type() == STRING_ITEM)
{
Item* conv= 0;
Item_arena *arena= thd->current_arena, backup;
strong= coll.strong;
weak= strong ? 0 : 1;
/*
In case we're in statement prepare, create conversion item
in its memory: it will be reused on each execute.
*/
if (arena->is_stmt_prepare())
thd->set_n_backup_item_arena(arena, &backup);
if (args[weak]->type() == STRING_ITEM)
uint conv_errors;
String tmp, cstr, *ostr= args[weak]->val_str(&tmp);
cstr.copy(ostr->ptr(), ostr->length(), ostr->charset(),
args[strong]->collation.collation, &conv_errors);
if (conv_errors)
{
String tmp, cstr;
String *ostr= args[weak]->val_str(&tmp);
cstr.copy(ostr->ptr(), ostr->length(), ostr->charset(),
args[strong]->collation.collation);
conv= new Item_string(cstr.ptr(),cstr.length(),cstr.charset(),
args[weak]->collation.derivation);
((Item_string*)conv)->str_value.copy();
/*
We could not convert a string into the character set
of the stronger side of the operation without data loss.
It can happen if we tried to combine a column with a string
constant, and the column charset does not cover all the
characters from the string. Operation cannot be done
correctly. Return an error.
*/
my_coll_agg_error(args[0]->collation, args[1]->collation,
func_name());
return;
}
else
{
conv= new Item_func_conv_charset(args[weak],
args[strong]->collation.collation);
conv->collation.set(args[weak]->collation.derivation);
conv->fix_fields(thd, 0, &conv);
}
if (arena->is_stmt_prepare())
thd->restore_backup_item_arena(arena, &backup);
args[weak]= conv ? conv : args[weak];
conv= new Item_string(cstr.ptr(),cstr.length(),cstr.charset(),
args[weak]->collation.derivation);
((Item_string*)conv)->str_value.copy();
}
else
{
if (!(coll.collation->state & MY_CS_UNICODE))
{
/*
Don't allow automatic conversion to non-Unicode charsets,
as it potentially loses data.
*/
my_coll_agg_error(args[0]->collation, args[1]->collation,
func_name());
return;
}
conv= new Item_func_conv_charset(args[weak],
args[strong]->collation.collation);
conv->collation.set(args[weak]->collation.derivation);
conv->fix_fields(thd, 0, &conv);
}
if (arena->is_stmt_prepare())
thd->restore_backup_item_arena(arena, &backup);
args[weak]= conv ? conv : args[weak];
}
// Make a special case of compare with fields to get nicer DATE comparisons
@@ -1782,14 +1807,13 @@ void Item_func_in::fix_length_and_dec()
via creating Item_func_conv_charset().
*/
if (agg_arg_collations_for_comparison(cmp_collation,
args, arg_count, TRUE))
if (agg_arg_collations_for_comparison(cmp_collation, args, arg_count,
MY_COLL_ALLOW_SUPERSET_CONV))
return;
if ((!my_charset_same(args[0]->collation.collation,
cmp_collation.collation) || !const_itm))
{
if (agg_arg_collations_for_comparison(cmp_collation,
args, arg_count, FALSE))
if (agg_arg_collations_for_comparison(cmp_collation, args, arg_count))
return;
}
else