"DECLARE CURSOR FOR SHOW ..." is a syntax that currently appears to work,
but is untested for some SHOW commands and does not work for other SHOW
commands.
Since this is an un-intended feature that leaked as a result of a coding bug
(in the parser grammar), the correct fix is to fix the grammar to not accept
this construct.
In other words, "DECLARE CURSOR FOR SHOW <other commands that don't work>"
is not considered a bug, and we will not implement other features to make all
the SHOW commands usable inside a cursor just because someone exploited a bug.
This deadlock occurs when a client issues a HANDLER ... OPEN statement
that tries to open a table that has a pending name-lock on it by another
client that also needs a name-lock on some other table which is already
open and associated to a HANDLER instance owned by the first client.
The deadlock happens because the open_table() function will back-off
and wait until the name-lock goes away, causing a circular wait if some
other name-lock is also pending for one of the open HANDLER tables.
Such situation, for example, can be easily repeated by issuing a RENAME
TABLE command in such a way that the existing table is already open
as a HANDLER table by another client and this client tries to open
a HANDLER to the new table name.
The solution is to allow handler tables with older versions (marked for
flush) to be closed before waiting for the name-lock completion. This is
safe because no other name-lock can be issued between the flush and the
check for pending name-locks.
The test case for this bug is going to be committed into 5.1 because it
requires a test feature only avaiable in 5.1 (wait_condition).
when used in a VIEW.
The problem was that wrong function (create_tmp_from_item())
was used to create a temporary field for Item_func_sp.
The fix is to use create_tmp_from_field().
This bug is a symptom of the way handler's tables are managed. The
most different aspect, compared to the conventional behavior, is that
the handler's tables are long lived, meaning that their lifetimes are
not bounded by the duration of the command that opened them. For this
effect the handler code uses its own list (handler_tables instead of
open_tables) to hold open handler tables so that the tables won't be
closed at the end of the command/statement. Besides the handler_tables
list, there is a hash (handler_tables_hash) which is used to associate
handler aliases to tables and to refresh the tables upon demand (flush
tables).
The current implementation doesn't work properly with refreshed tables
-- more precisely when flush commands are issued by other initiators.
This happens because when a handler open or read statement is being
processed, the associated table has to be opened or locked and, for this
matter, the open_tables and handler_tables lists are swapped so that the
new table being opened is inserted into the handler_tables list. But when
opening or locking the table, if the refresh version is different from the
thread refresh version then all used tables in the open_tables list (now
handler_tables) are refreshed. In the "refreshing" process the handler
tables are flushed (closed) without being properly unlinked from the
handler hash.
The current implementation also fails to properly discard handlers of
dropped tables, but this and other problems are going to be addressed
in the fixes for bugs 31397 and 31409.
The chosen approach tries to properly save and restore the table state
so that no table is flushed during the table open and lock operations.
The logic is almost the same as before with the list swapping, but with
a working glue code.
The test case for this bug is going to be committed into 5.1 because it
requires a test feature only avaiable in 5.1 (wait_condition).
This actually, fix for the patch for bug-27354. The problem with
the patch was that Item_func_sp::used_tables() was updated, but
Item_func_sp::const_item() was not. So, for Item_func_sp, we had
the following inconsistency:
- used_tables() returned RAND_TABLE, which means that the item
can produce "random" results;
- but const_item() returned TRUE, which means that the item is
a constant one.
The fix is to change Item_func_sp::const_item() behaviour: it must
return TRUE (an item is a constant one) only if a stored function
is deterministic and each of its arguments (if any) is a constant
item.
were accidentally removed during a previous rototill of this
code. Fixes bug#27692.
While it can be argued we should strive to provide a 'secure by
default' installation, this happens to be the setup currently
documented in the manual as the default, so defer changes that
improve security out of the box to a co-ordinated effort later
on.
For now, make a note about the test databases and anonymous user
in mysql_install_db and recommend that mysql_secure_installation
be ran for users wishing to remove these defaults.
[..re-commit of previously lost change..]
It's not possible to use WaitForSingleObject to wait
on a CRITICAL_SECTION, instead use the TryEnterCriticalSection function.
- if "mutex" was already taken => return EBUSY
- if "mutex" was aquired => return 0
