- 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;
When the same VIEW was created at the master side twice,
malformed (truncated after the word 'AS') query string
was forwarded to client side, so error messages on the
master and client was different, and replication was
broken.
The mysql_register_view function call failed
too early: fields of `view' output argument of this
function was not filled yet with correct data required
for query replication.
The mysql_register_view function also copied pointers to
local buffers into a memory allocated by the caller.
When we write 'query=...' string to a frm file for views on a slave,
indentifiers are not properly quoted due to missing OPTION_QUOTE_SHOW_CREATE
flag in the thd->options.
Fix: properly set thd->options for the slave thread.
can be not replicable.
Now CREATE statements for writing in the binlog are created as follows:
- the beginning of the statement is re-created;
- the rest of the statement is copied from the original query.
The problem appears when there is a version-specific comment (produced by
mysqldump), started in the re-created part of the statement and closed in the
copied part -- there is closing comment-parenthesis, but there is no opening
one.
The proper fix could be to re-create original statement, but we can not
implement it in 5.0. So, for 5.0 the fix is just to cut closing
comment-parenthesis. This technique is also used for SHOW CREATE PROCEDURE
statement (so we are able to reuse existing code).
