Wrong criteria was used to distinguish the case when there was no
lookahead performed in the parser. Bug affected only statements
ending in one-character token without any optional tail, like CREATE
INDEX and CALL.
The problem was that we restored SQL_CACHE, SQL_NO_CACHE flags in SELECT
statement from internal structures based on value set later at runtime, not
the original value set by the user.
The solution is to remember that original value.
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.
Addendum fixes after changing the condition variable
for the global read lock.
The stress test suite revealed some deadlocks. Some were
related to the new condition variable (COND_global_read_lock)
and some were general problems with the global read lock.
It is now necessary to signal COND_global_read_lock whenever
COND_refresh is signalled.
We need to wait for the release of a global read lock if one
is set before every operation that requires a write lock.
But we must not wait if we have locked tables by LOCK TABLES.
After setting a global read lock a thread waits until all
write locks are released.
The problem was a call to convert_dirname() with a destination buffer
that did not have room for the trailing slash added by that function.
This could cause the instance manager to crash in some cases.
An UNIQUE KEY consisting of NOT NULL columns
was displayed as PRIMARY KEY in "DESC t1".
According to the code, that was intentional
behaviour for some reasons unknown to me.
This code was written before bitkeeper time,
so I cannot check who and why made this.
After discussing on dev-public, a decision
was made to remove this code
- The setting of "ENV{'TZ'}" doesn't affect the timezone
used by MySQL Server on Windows.
- Explicitly set timezone in test cases before doing UTC/localtime
conversions so tests produce deterministic results
- The setting of "ENV{'TZ'}" doesn't affect the timezone
used by MySQL Server on Windows.
- Explicitly set timezone to "+03:00" in test case before
doing the calculatiosn to check that there is three hours
difference between utc and local time.
(Magnus' fix)
with PREPARE fails with weird error".
More generally, re-executing a stored procedure with a complex SP cursor query
could lead to a crash.
The cause of the problem was that SP cursor queries were not optimized
properly at first execution: their parse tree belongs to sp_instr_cpush,
not sp_instr_copen, and thus the tree was tagged "EXECUTED" when the
cursor was declared, not when it was opened. This led to loss of optimization
transformations performed at first execution, as sp_instr_copen saw that the
query is already "EXECUTED" and therefore either not ran first-execution
related blocks or wrongly rolled back the transformations caused by
first-execution code.
The fix is to update the state of the parsed tree only when the tree is
executed, as opposed to when the instruction containing the tree is executed.
Assignment if i->state is moved to reset_lex_and_exec_core.
The problem was in redundant calls to strlen() in string functions,
where we may then return after checking only the small number of characters.
No test case is provided since it's a performance fix.
This bug in Field_string::cmp resulted in a wrong comparison
with keys in partial indexes over multi-byte character fields.
Given field a is declared as a varchar(16) collate utf8_unicode_ci
INDEX(a(4)) gives us an example of such an index.
Wrong key comparisons could lead to wrong result sets if
the selected query execution plan used a range scan by
a partial index over a utf8 character field.
This also caused wrong results in many other cases.
