The bug happens because of a combination of unfortunate circumstances:
1. Arguments args[0] and args[2] of Item_func_concat point recursively
(through Item_direct_view_ref's) to the same Item_func_conv_charset.
Both args[0]->args[0]->ref[0] and args[2]->args[0]->ref[0] refer to
this Item_func_conv_charset.
2. When Item_func_concat::args[0]->val_str() is called,
Item_func_conv_charset::val_str() writes its result to
Item_func_conc_charset::tmp_value.
3. Then, for optimization purposes (to avoid copying),
Item_func_substr::val_str() initializes Item_func_substr::tmp_value
to point to the buffer fragment owned by Item_func_conv_charset::tmp_value
Item_func_substr::tmp_value is returned as a result of
Item_func_concat::args[0]->val_str().
4. Due to optimization to avoid memory reallocs,
Item_func_concat::val_str() remembers the result of args[0]->val_str()
in "res" and further uses "res" to collect the return value.
5. When Item_func_concat::args[2]->val_str() is called,
Item_func_conv_charset::tmp_value gets overwritten (see #1),
which effectively overwrites args[0]'s Item_func_substr::tmp_value (see #3),
which effectively overwrites "res" (see #4).
This patch does the following:
a. Changes Item_func_conv_charset::val_str(String *str) to use
tmp_value and str the other way around. After this change tmp_value
is used to store a temporary result, while str is used to return the value.
The fixes the second problem (without SUBSTR):
SELECT CONCAT(t2,'-',t2) c2
FROM (SELECT CONVERT(t USING latin1) t2 FROM t1) sub;
As Item_func_concat::val_str() supplies two different buffers when calling
args[0]->val_str() and args[2]->val_str(), in the new reduction the result
created during args[0]->val_str() does not get overwritten by
args[2]->val_str().
b. Fixing the same problem in val_str() for similar classes
Item_func_to_base64
Item_func_from_base64
Item_func_weight_string
Item_func_hex
Item_func_unhex
Item_func_quote
Item_func_compress
Item_func_uncompress
Item_func_des_encrypt
Item_func_des_decrypt
Item_func_conv_charset
Item_func_reverse
Item_func_soundex
Item_func_aes_encrypt
Item_func_aes_decrypt
Item_func_buffer
c. Fixing Item_func::val_str_from_val_str_ascii() the same way.
Now Item_str_ascii_func::ascii_buff is used for temporary value,
while the parameter passed to val_str() is used to return the result.
This fixes the same problem when conversion (from ASCII to e.g. UCS2)
takes place. See the ctype_ucs.test for example queries that returned
wrong results before the fix.
d. Some Item_func descendand classes had temporary String buffers
(tmp_value and tmp_str), but did not really use them.
Removing these temporary buffers from:
Item_func_decode_histogram
Item_func_format
Item_func_binlog_gtid_pos
Item_func_spatial_collection:
e. Removing Item_func_buffer::tmp_value, because it's not used any more.
f. Renaming Item_func_[un]compress::buffer to "tmp_value",
for consistency with other classes.
Note, this patch does not fix the following classes
(although they have a similar problem):
Item_str_conv
Item_func_make_set
Item_char_typecast
They have a complex implementations and simple swapping between "tmp_value"
and "str" won't work. These classes will be fixed separately.
This is a join patch fixing these two bugs:
MDEV-12560 Wrong data type for SELECT NULL UNION SELECT Point(1,1)
MDEV-12665 Hybrid functions do not preserve geometry type
This patch does the following:
1. Adds a new method Type_handler_hybrid_field_type::aggregate_for_min_max()
- For non-traditional data types it uses
type_handler_data->m_type_aggregator_for_result.find_handler()
This allows pluggable data types to define in the future their
own behavior of the result data type detection for LEAST/GREATEST.
Also, this disallows expressions of the GEOMETRY data type
(and its variants such as POINT) to be mixed in with
numeric and temporal data types in LEAST/GREATEST.
- For traditional data types it reproduces the old behavior of
the result data type detection (but not attributes, see below).
2. Adds a new virtual method Type_handler::Item_func_min_max_fix_attributes()
and reuses as much as possible the code that calculates data type attributes
for CASE-alike functions (e.g. CASE..THEN, COALESCE, IF).
As the old code responsible for attributes calculation in the old
implementation of Item_func_min_max::fix_length_and_dec()
was not fully correct, this automatically fixes the following bugs:
- MDEV-12497 Wrong data type for LEAST(latin1_expr, utf8_expr)
The old fix_length_and_dec() calculated max_length before
character set aggregation. Now max_length is calculated after, in
Item_func::count_string_length() called from
Item_func::aggregate_attributes_string() called from
Type_handler_string_result::Item_hybrid_func_fix_attributes() called from
Type_handler::Item_func_min_max_fix_attributes() called from
Item_func_min_max::fix_length_and_dec().
- MDEV-12504 Wrong data type for LEAST(date_expr,time_expr)
The old fix_length_and_dec() simply used the maximum of max_length
among all arguments to set its own max_length and did not take
into account that a mixture of DATE and TIME becomes DATETIME.
Now this is correctly handled by:
Type_handler_datetime_common::Item_hybrid_func_fix_attributes() called from
Type_handler::Item_func_min_max_fix_attributes() called from
Item_func_min_max::fix_length_and_dec().
3. Removes the old implementation of Item_func_min_max::fix_length_and_dec()
and replaces it to calls of the new methods.
4. Cleanup: moves the code related to unsigned_flag processing
from Type_handler_hybrid_field_type::aggregate_for_result()
to Type_handler_int_result::Item_hybrid_func_fix_attributes().
This is done:
- to avoid code duplication in
Type_handler_hybrid_field_type::aggregate_for_min_max()
- to get rid of one more call for field_type(), which is unfriendly
to the conceipt of pluggable data types.
This patch implements MDEV-12514 according to the task descriptions.
It automatically fixes:
MDEV-12515 Wrong value when storing DATE_ADD() and ADDTIME() to a numeric field
Additionally:
a. Moves Item_func::set_attributes_temporal() to
Type_str_attributes::fix_attributes_temporal(),
which is a more proper place and name for it.
b. Continues replacing calls for:
set_handler_by_field_type(MYSQL_TYPE_XXX)
to corresponding:
set_handler(&type_handler_xxx)
which is faster.
Note, we should eventually get rid of almost all set_handler_by_field_type().
c. Makes type_handler_string, type_handler_time2, type_handler_newdate,
type_handler_datetime2 public.
(all built-in handlers will become public eventually)
d. Removing Item_temporal_func::sql_mode, as it was not used.
Make SELECT <columns> FROM I_S.TABLES behave identically independently
from whether <columns> require opening the table in engine or
<columns> can be filled with only opening the frm.
In particular, fill_schema_table_from_frm() should not silently skip
frms with unknown engine, but should fill the I_S.TABLES row
with NULLs just like fill_schema_table_by_open() does.
This patch makes the following changes (according to the task description):
- Adds Type_handler::Item_func_round_fix_length_and_dec().
- Splits the code from Item_func_round::fix_length_and_dec() into new
Item_func_round methods fix_arg_int(), fix_arg_decimal(), fix_arg_double().
- Calls the new Item_func_round methods from the relevant implementations of
Type_handler_xxx::Item_func_round_fix_length_and_dec().
- Adds a new error message ER_ILLEGAL_PARAMETER_DATA_TYPE_FOR_OPERATION
- Makes ROUND() return the new error for GEOMETRY
Additionally:
- Inherits Item_func_round directly from Item_func_numhybrid as it
uses nothing from Item_func_num1.
- Fixes "MDEV-12000 ROUND(expr,const_expr_returning_NULL) creates DOUBLE(0,0)".
Now if args[1] returns NULL, the data type is set to DOUBLE with
NOT_FIXED_DEC decimals instead of 0 decimals.
- Adding SHOW CREATE TABLE into all DEFAULT tests,
to cover need_parentheses_in_default() for all items
- Fixing a few items not to print parentheses in DEFAULT:
spatial function-alike predicates, IS_IPV4 and IS_IPV6 functions,
COLUMN_CHECK() and COLUMN_EXISTS().
Problem was that we considered the point itself as the 'border' object. Instead
of that the 'border' of a POINT is an empty set, and the point is the 'interior'.
Another error fixed by the way - not all operations of the resulting function were properly
allocated.
- Renaming Item::is_bool_func() to is_bool_type(), to avoid assumption
that the item is an Item_func derivant.
- Deriving Item_func_spatial_rel from Item_bool_func rather than Item_int_func
When the distance in ST_BUFFER is too far negative the coordinates can run out of the operational
area. We should just return an empty geometry in this case.
The GEOMETRY field metadata is stored in the FRM file.
SRID for a spatial column now can be stored, it was added to the CREATE TABLE syntax,
so the AddGeometryData() stored procedure is now possible. Script adding the required Add/DropGeometryColumn sp-s added.
