mariadb/sql/sql_schema.cc
Alexander Barkov 2b6d241ee4 MDEV-27744 LPAD in vcol created in ORACLE mode makes table corrupted in non-ORACLE
The crash happened with an indexed virtual column whose
value is evaluated using a function that has a different meaning
in sql_mode='' vs sql_mode=ORACLE:

- DECODE()
- LTRIM()
- RTRIM()
- LPAD()
- RPAD()
- REPLACE()
- SUBSTR()

For example:

CREATE TABLE t1 (
  b VARCHAR(1),
  g CHAR(1) GENERATED ALWAYS AS (SUBSTR(b,0,0)) VIRTUAL,
  KEY g(g)
);

So far we had replacement XXX_ORACLE() functions for all mentioned function,
e.g. SUBSTR_ORACLE() for SUBSTR(). So it was possible to correctly re-parse
SUBSTR_ORACLE() even in sql_mode=''.

But it was not possible to re-parse the MariaDB version of SUBSTR()
after switching to sql_mode=ORACLE. It was erroneously mis-interpreted
as SUBSTR_ORACLE().

As a result, this combination worked fine:

SET sql_mode=ORACLE;
CREATE TABLE t1 ... g CHAR(1) GENERATED ALWAYS AS (SUBSTR(b,0,0)) VIRTUAL, ...;
INSERT ...
FLUSH TABLES;
SET sql_mode='';
INSERT ...

But the other way around it crashed:

SET sql_mode='';
CREATE TABLE t1 ... g CHAR(1) GENERATED ALWAYS AS (SUBSTR(b,0,0)) VIRTUAL, ...;
INSERT ...
FLUSH TABLES;
SET sql_mode=ORACLE;
INSERT ...

At CREATE time, SUBSTR was instantiated as Item_func_substr and printed
in the FRM file as substr(). At re-open time with sql_mode=ORACLE, "substr()"
was erroneously instantiated as Item_func_substr_oracle.

Fix:

The fix proposes a symmetric solution. It provides a way to re-parse reliably
all sql_mode dependent functions to their original CREATE TABLE time meaning,
no matter what the open-time sql_mode is.

We take advantage of the same idea we previously used to resolve sql_mode
dependent data types.

Now all sql_mode dependent functions are printed by SHOW using a schema
qualifier when the current sql_mode differs from the function sql_mode:

SET sql_mode='';
CREATE TABLE t1 ... SUBSTR(a,b,c) ..;
SET sql_mode=ORACLE;
SHOW CREATE TABLE t1;   ->   mariadb_schema.substr(a,b,c)

SET sql_mode=ORACLE;
CREATE TABLE t2 ... SUBSTR(a,b,c) ..;
SET sql_mode='';
SHOW CREATE TABLE t1;   ->   oracle_schema.substr(a,b,c)

Old replacement names like substr_oracle() are still understood for
backward compatibility and used in FRM files (for downgrade compatibility),
but they are not printed by SHOW any more.
2023-11-08 15:01:20 +04:00

168 lines
5 KiB
C++

/*
Copyright (c) 2020, MariaDB Corporation.
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 02110-1335 USA */
#include "mariadb.h"
#include "sql_type.h"
#include "sql_schema.h"
#include "sql_class.h"
class Schema_oracle: public Schema
{
public:
Schema_oracle(const LEX_CSTRING &name)
:Schema(name)
{ }
const Type_handler *map_data_type(THD *thd, const Type_handler *src)
const
{
if (src == &type_handler_newdate)
return thd->type_handler_for_datetime();
return src;
}
Create_func *find_native_function_builder(THD *thd, const LEX_CSTRING &name)
const
{
return native_functions_hash_oracle.find(thd, name);
}
Item *make_item_func_replace(THD *thd,
Item *subj,
Item *find,
Item *replace) const;
Item *make_item_func_substr(THD *thd,
const Lex_substring_spec_st &spec) const;
Item *make_item_func_trim(THD *thd, const Lex_trim_st &spec) const;
};
class Schema_maxdb: public Schema
{
public:
Schema_maxdb(const LEX_CSTRING &name)
:Schema(name)
{ }
const Type_handler *map_data_type(THD *thd, const Type_handler *src)
const
{
if (src == &type_handler_timestamp ||
src == &type_handler_timestamp2)
return thd->type_handler_for_datetime();
return src;
}
};
Schema mariadb_schema(Lex_cstring(STRING_WITH_LEN("mariadb_schema")));
Schema_oracle oracle_schema(Lex_cstring(STRING_WITH_LEN("oracle_schema")));
Schema_maxdb maxdb_schema(Lex_cstring(STRING_WITH_LEN("maxdb_schema")));
const Schema &oracle_schema_ref= oracle_schema;
Schema *Schema::find_by_name(const LEX_CSTRING &name)
{
DBUG_ASSERT(name.str);
if (mariadb_schema.eq_name(name))
return &mariadb_schema;
if (oracle_schema.eq_name(name))
return &oracle_schema;
if (maxdb_schema.eq_name(name))
return &maxdb_schema;
return NULL;
}
Schema *Schema::find_implied(THD *thd)
{
if (thd->variables.sql_mode & MODE_ORACLE)
return &oracle_schema;
if (thd->variables.sql_mode & MODE_MAXDB)
return &maxdb_schema;
return &mariadb_schema;
}
Create_func *
Schema::find_native_function_builder(THD *thd, const LEX_CSTRING &name) const
{
return native_functions_hash.find(thd, name);
}
Item *Schema::make_item_func_call_native(THD *thd,
const Lex_ident_sys &name,
List<Item> *args) const
{
Create_func *builder= find_native_function_builder(thd, name);
if (builder)
return builder->create_func(thd, &name, args);
my_error(ER_FUNCTION_NOT_DEFINED, MYF(0), name.str);
return NULL;
}
Item *Schema::make_item_func_replace(THD *thd,
Item *subj,
Item *find,
Item *replace) const
{
return new (thd->mem_root) Item_func_replace(thd, subj, find, replace);
}
Item *Schema::make_item_func_substr(THD *thd,
const Lex_substring_spec_st &spec) const
{
return spec.m_for ?
new (thd->mem_root) Item_func_substr(thd, spec.m_subject, spec.m_from,
spec.m_for) :
new (thd->mem_root) Item_func_substr(thd, spec.m_subject, spec.m_from);
}
Item *Schema::make_item_func_trim(THD *thd, const Lex_trim_st &spec) const
{
return spec.make_item_func_trim_std(thd);
}
Item *Schema_oracle::make_item_func_replace(THD *thd,
Item *subj,
Item *find,
Item *replace) const
{
return new (thd->mem_root) Item_func_replace_oracle(thd, subj, find, replace);
}
Item *Schema_oracle::make_item_func_substr(THD *thd,
const Lex_substring_spec_st &spec) const
{
return spec.m_for ?
new (thd->mem_root) Item_func_substr_oracle(thd, spec.m_subject,
spec.m_from,
spec.m_for) :
new (thd->mem_root) Item_func_substr_oracle(thd, spec.m_subject,
spec.m_from);
}
Item *Schema_oracle::make_item_func_trim(THD *thd,
const Lex_trim_st &spec) const
{
return spec.make_item_func_trim_oracle(thd);
}