MySQL Bugs: #21249: Character set of SP-var can be ignored

Bug #21249	Character set of SP-var can be ignored
Submitted:	24 Jul 2006 12:51	Modified:	11 Jul 2007 19:52
Reporter:	Alexander Nozdrin	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Stored Routines	Severity:	S2 (Serious)
Version:	5.0.24/5.0/5.1BK	OS:	Any
Assigned to:	Alexander Nozdrin	CPU Architecture:	Any
Tags:	rt_q1_2007

Description:
This bug is quite similar to BUG#16211 (Stored function return type for strings
is ignored), but deals with stored routine variables. The problem is that
if character set of SP-variable is not explicitly specified, CHARSET-clause
is not appended. Thus, if the database character set is altered, character set
of SP-var is also changed.

How to repeat:
mysql> create database db1 character set cp1251;
mysql> use db1
mysql> delimiter |
mysql> create procedure p1(p char)
    -> begin
    ->   declare v1 char(10);
    ->   select charset(p);
    ->   select charset(v1);
    -> end|

mysql> call p1('a')|
+------------+
| charset(p) |
+------------+
| cp1251     |
+------------+

+-------------+
| charset(v1) |
+-------------+
| cp1251      |
+-------------+

mysql> show create procedure p1 \G
*************************** 1. row ***************************
       Procedure: p1
        sql_mode:
Create Procedure: CREATE DEFINER=`root`@`localhost` PROCEDURE `p1`(p char)
begin
  declare v1 char(10);
  select charset(p);
  select charset(v1);
end

-- NOTE: there is no CHARSET-clause in declaration of SP-variables.

mysql> alter database db1 character set koi8r;

-- NOTE: changing the connection to reset stored routine cache.

mysql> Bye

mysql> call p1('a');
+------------+
| charset(p) |
+------------+
| koi8r      |
+------------+

+-------------+
| charset(v1) |
+-------------+
| koi8r       |
+-------------+

Suggested fix:
Like in BUG#16211, add CHARSET-clause even if it is not specified explicitly
in CREATE statement.

Thank you for the bug report. Verified as described.

Queued into 5.1-runtime

Also was reviewed by Alexander Barkov

ChangeSet
  anozdrin/alik@ibm.|ChangeSet|20070628173454|18968    2007/06/28 21:34:54+04:00
anozdrin@ibm. +82 -0
  Patch for the following bugs:
    - BUG#11986: Stored routines and triggers can fail if the code
      has a non-ascii symbol
    - BUG#16291: mysqldump corrupts string-constants with non-ascii-chars
    - BUG#19443: INFORMATION_SCHEMA does not support charsets properly
    - BUG#21249: Character set of SP-var can be ignored
    - BUG#25212: Character set of string constant is ignored (stored routines)
    - BUG#25221: Character set of string constant is ignored (triggers)
  
  There were a few general problems that caused these bugs:
  1. Character set information of the original (definition) query for views,
     triggers, stored routines and events was lost.
  2. mysqldump output query in client character set, which can be
     inappropriate to encode definition-query.
  3. INFORMATION_SCHEMA used strings with mixed encodings to display object
     definition;
  
  1. No query-definition-character set.
  
  In order to compile query into execution code, some extra data (such as
  environment variables or the database character set) is used. The problem
  here was that this context was not preserved. So, on the next load it can
  differ from the original one, thus the result will be different.
  
  The context contains the following data:
    - client character set;
    - connection collation (character set and collation);
    - collation of the owner database;
  
  The fix is to store this context and use it each time we parse (compile)
  and execute the object (stored routine, trigger, ...).
  
  2. Wrong mysqldump-output.
  
  The original query can contain several encodings (by means of character set
  introducers). The problem here was that we tried to convert original query
  to the mysqldump-client character set.
  
  Moreover, we stored queries in different character sets for different
  objects (views, for one, used UTF8, triggers used original character set).
  
  The solution is
    - to store definition queries in the original character set;
    - to change SHOW CREATE statement to output definition query in the
      binary character set (i.e. without any conversion);
    - introduce SHOW CREATE TRIGGER statement;
    - to dump special statements to switch the context to the original one
      before dumping and restore it afterwards.
  
  Note, in order to preserve the database collation at the creation time,
  additional ALTER DATABASE might be used (to temporary switch the database
  collation back to the original value). In this case, ALTER DATABASE
  privilege will be required. This is a backward-incompatible change.
  
  3. INFORMATION_SCHEMA showed non-UTF8 strings
  
  The fix is to generate UTF8-query during the parsing, store it in the object
  and show it in the INFORMATION_SCHEMA.
  
  Basically, the idea is to create a copy of the original query convert it to
  UTF8. Character set introducers are removed and all text literals are
  converted to UTF8.
  
  This UTF8 query is intended to provide user-readable output. It must not be
  used to recreate the object.  Specialized SHOW CREATE statements should be
  used for this.
  
  The reason for this limitation is the following: the original query can
  contain symbols from several character sets (by means of character set
  introducers).
  
  Example:
  
    - original query:
      CREATE VIEW v1 AS SELECT _cp1251 'Hello' AS c1;
  
    - UTF8 query (for INFORMATION_SCHEMA):
      CREATE VIEW v1 AS SELECT 'Hello' AS c1;

Pushed into 5.1.21-beta

Noted in 5.1.21 changelog.

(Description applies to Bug#11986, Bug#16291, Bug#19443,
Bug#21249, Bug#25212, Bug#25221)

Several issues were identified for stored programs
containing non-ASCII symbols. These issues involved
conversion errors due to incomplete character set
information when translating these objects to and from
stored format, such as:

* Parsing the original object definition so that it
  can be stored.

* Compiling the stored definition into executable form
  when the object is invoked.

* Retrieval of object definitions from 
  INFORMATION_SCHEMA tables.

* Displaying the object definition in SHOW statements.
  This issue also affected mysqldump, which uses SHOW.

The fix for the problems is to store character set
information from the object creation context so that this
information is available when the object needs to be used
later. The context includes the client character set, the
connection character set and collation, and the collation
of the database with which the object is associated.
As a result of the patch, several tables have new
columns:

* In the mysql database, the proc and event tables now
  have these columns: character_set_client, 
  collation_connection, db_collation, body_utf8.

* In INFORMATION_SCHEMA, the VIEWS table now has these
  columns: CHARACTER_SET_CLIENT, COLLATION_CONNECTION.
  The ROUTINES, TRIGGERS, and EVENT tables now have
  these columns: CHARACTER_SET_CLIENT,
  COLLATION_CONNECTION, DATABASE_COLLATION.

These columns store the session values of the
character_set_client and collation_connection system
variables, and the collation of the database with which
the object is associated. The values are those in effect
at object creation time. (The saved database collation is
not the value of the collation_database system variable,
which applies to the default database; the database that
contains the object is not necessarily the default
database.)

Several SHOW statements now display additional columns
corresponding to the new table columns. These statements
are: SHOW CREATE EVENT, SHOW CREATE FUNCTION, SHOW CREATE
PROCEDURE, SHOW CREATE VIEW, SHOW EVENTS, SHOW FUNCTION
STATUS, SHOW PROCEDURE STATUS, SHOW TRIGGERS.