The implementation of the method Item_func_reverse::val_str
for the REVERSE function modified the argument of the function.
This led to wrong results for expressions that contained
REVERSE(ref) if ref occurred somewhere else in the expressions.
Bug#19022 "Memory bug when switching db during trigger execution"
Bug#17199 "Problem when view calls function from another database."
Bug#18444 "Fully qualified stored function names don't work correctly in
SELECT statements"
Documentation note: this patch introduces a change in behaviour of prepared
statements.
This patch adds a few new invariants with regard to how THD::db should
be used. These invariants should be preserved in future:
- one should never refer to THD::db by pointer and always make a deep copy
(strmake, strdup)
- one should never compare two databases by pointer, but use strncmp or
my_strncasecmp
- TABLE_LIST object table->db should be always initialized in the parser or
by creator of the object.
For prepared statements it means that if the current database is changed
after a statement is prepared, the database that was current at prepare
remains active. This also means that you can not prepare a statement that
implicitly refers to the current database if the latter is not set.
This is not documented, and therefore needs documentation. This is NOT a
change in behavior for almost all SQL statements except:
- ALTER TABLE t1 RENAME t2
- OPTIMIZE TABLE t1
- ANALYZE TABLE t1
- TRUNCATE TABLE t1 --
until this patch t1 or t2 could be evaluated at the first execution of
prepared statement.
CURRENT_DATABASE() still works OK and is evaluated at every execution
of prepared statement.
Note, that in stored routines this is not an issue as the default
database is the database of the stored procedure and "use" statement
is prohibited in stored routines.
This patch makes obsolete the use of check_db_used (it was never used in the
old code too) and all other places that check for table->db and assign it
from THD::db if it's NULL, except the parser.
How this patch was created: THD::{db,db_length} were replaced with a
LEX_STRING, THD::db. All the places that refer to THD::{db,db_length} were
manually checked and:
- if the place uses thd->db by pointer, it was fixed to make a deep copy
- if a place compared two db pointers, it was fixed to compare them by value
(via strcmp/my_strcasecmp, whatever was approproate)
Then this intermediate patch was used to write a smaller patch that does the
same thing but without a rename.
TODO in 5.1:
- remove check_db_used
- deploy THD::set_db in mysql_change_db
See also comments to individual files.
Fix for bug#16716 for --ps-protocol mode.
item_cmpfunc.cc:
Fix for a memory allocation/freeing problem in agg_cmp_type() after fix
for bug#16377. Few language corrections.
To calculate its max_length the CONCAT() function is simply sums max_lengths
of its arguments but when the collation of an argument differs from the
collation of the CONCAT() max_length will be wrong. This may lead to a data
truncation when a tmp table is used, in UNIONS for example.
The Item_func_concat::fix_length_and_dec() function now recalculates the
max_length of an argument when the mbmaxlen of the argument differs from the
mbmaxlen of the CONCAT().
argument can lead to a wrong result.
md5() and sha() functions treat their arguments as case sensitive strings.
But when they are compared their arguments were compared as a case
insensitive strings which leads to two functions with different arguments
and thus different results to being identical. This can lead to a wrong
decision made in the range optimizer and thus lead to a wrong result set.
Item_func_md5::fix_length_and_dec() and Item_func_sha::fix_length_and_dec()
functions now set binary collation on their arguments.
The Item_func_concat::val_str() function tries to make as less re-allocations
as possible. This results in appending strings returned by 2nd and next
arguments to the string returned by 1st argument if the buffer for the first
argument has enough free space. A constant subselect is evaluated only once
and its result is stored in an Item_cache_str. In the case when the first
argument of the concat() function is such a subselect Item_cache_str returns
the stored value and Item_func_concat::val_str() append values of other
arguments to it. But for the next row the value in the Item_cache_str isn't
restored because the subselect is a constant one and it isn't evaluated second
time. This results in appending string values of 2nd and next arguments to the
result of the previous Item_func_concat::val_str() call.
The Item_func_concat::val_str() function now checks whether the first argument
is a constant one and if so it doesn't append values of 2nd and next arguments
to the string value returned by it.
item_strfunc.h, item_strfunc.cc, item.cc:
Try to convert a const item into destination
character set. If conversion happens without
data loss, then cache the converted value
and return it during val_str().
Otherwise, if conversion loses data, return
Illeral mix of collations error, as it happened
previously.
ctype_recoding.result, ctype_recoding.test:
Fixing tests accordingly.
Bad examples of usage of a string with its length fixed.
The incorrect length in the trigger file configuration descriptor
fixed (BUG#14090).
A hook for unknown keys added to the parser to support old .TRG files.
ctype_utf8.result, ctype_utf8.test:
Adding test case.
item_strfunc.cc:
item_strfunc.h:
Moving the well formed checking code into a method,
to reuse in several Item_func_xxx. Reusing the new
method in Item_func_char and Item_func_charset_conv.
- CHAR() now returns binary string as default
- CHAR(X*65536+Y*256+Z) is now equal to CHAR(X,Y,Z) independent of the character set for CHAR()
- Test for both ETIMEDOUT and ETIME from pthread_cond_timedwait()
(Some old systems returns ETIME and it's safer to test for both values
than to try to write a wrapper for each old system)
- Fixed new introduced bug in NOT BETWEEN X and X
- Ensure we call commit_by_xid or rollback_by_xid for all engines, even if one engine has failed
- Use octet2hex() for all conversion of string to hex
- Simplify and optimize code
problems which were introduced during work on WL#2787 "Add view definer/owner
to the view definition (.frm) to check privileges on used tables and stored
routines when using a VIEW."
In some cases it is better to use value from Security_context::host_or_ip
instead of value from Security_context::host since the latter can be NULL
in certain situations (When we can't resolve hostname or we have not done
this yet).
Character set does not support traditional mode
ctype_utf8.result, ctype_utf8.test:
adding test case.
password.c, mysql_com.h
Changeing octet2hex availability from static to public.
item_strfunc.cc:
Result string is now checked to be well-formed.
Warning/error is generated, depending on sql_mode.
BUG #11104
Took out the offset-=delimiter_length-1 out of the for loop. It was causing
basically this:
select substring_index('the king of the the hill', 'the', -2) to not work.
The first iteration, offset would be initialised to 24, then strstr would
point at 'the king of the the* hill' ('*'means right before the
character following), returning a offset of 16. The for loop would then
decrement offset by two (3 - 1), to 14, now pointing at
"the king of th*e the hill", _skipping_ past the 'e' in the second to last
'the', and therefore strstr would never have a chance of matching the
second to last 'the', then moving on to the 'the' at the begginning of the
string!
In a nutshell, offset was being decremented by too great a value, preventing
the second to last 'the' from being ever found, hence the result of
'king of the the hill' from the query that is reported in the bug report
func_str.test:
BUG #11104
Added tests to make sure fix addresses issues in original bug report
func_str.result:
BUG #11104
New results for new tests
adding test case
item_strfunc.cc:
Bug#12351
CONCAT with USER()/DATEBASE() and
a column gets strange results.
Mark created Item_str as constant, so CONCAT
cannot reuse it for optimization purposes.
