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.
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.
Under row-based replication, DELETE FROM will now always be
replicated as individual row deletions, while TRUNCATE TABLE will
always be replicated as a statement.
garbles data if longer than 766 chars.
The problem is that a stored routine returns BLOBs to the previous
caller, BLOBs are shallow-copied (i.e. only pointers to the data are
copied). The fix is to also copy data of BLOBs.
or implicitly uses stored function gives "Table not locked" error'
CREATE TABLE ... SELECT ... statement which was explicitly or implicitly
(through view) using stored function gave "Table not locked" error.
The actual bug resides in the current locking scheme of CREATE TABLE SELECT
code, which first opens and locks tables of the SELECT statement itself,
and then, having SELECT tables locked, creates the .FRM, opens the .FRM and
acquires lock on it. This scheme opens a possibility for a deadlock, which
was present and ignored since version 3.23 or earlier. This scheme also
conflicts with the invariant of the prelocking algorithm -- no table can
be open and locked while there are tables locked in prelocked mode.
The patch makes an exception for this invariant when doing CREATE TABLE ...
SELECT, thus extending the possibility of a deadlock to the prelocked mode.
We can't supply a better fix in 5.0.
a misnamed function
... in the presence of a continue handler. The problem was that with a
handler, it continued to execute as if function existed and had set a
useful return value (which it hadn't).
The fix is to set a null return value and do an error return when a function
wasn't found.
counter".
When TRUNCATE TABLE was called within an stored procedure the
auto_increment counter was not reset to 0 even if straight
TRUNCATE for this table did this.
This fix makes TRUNCATE in stored procedures to be handled exactly
in the same way as straight TRUNCATE. We achieve this by rolling
back the fix for bug 8850, which is no longer needed since stored
procedures don't require prelocked mode anymore (and TRUNCATE is
not allowed in stored functions or triggers).
fix_fields() was not called for "order by" variables if the type was a
"constant integer", and thus interpreted as a column index.
However, a local variable is an expression and should not be interpreted
as a column index. Instead it behaves just like when using a user variable
for instance (i.e. it will not affect the ordering).
produce wrong data
By default Item_sp_func::val_str() returns string from it's result_field
internal buffer. When grouping is present Item_copy_string is used to
store SP function result, but it doesn't additionally buffer the result.
When the next record is read, internal buffer is overwritten, due to
this Item_copy_string::val_str() will have wrong data. Thus producing
weird query result.
The Item_func_sp::val_str() now makes a copy of returned value to prevent
occasional corruption.
time per connection
Removed const_string() method from Item_string (it was only used in one
place, in a bad way). Defer possible SP variable, and access data directly
instead, in date_format item.
