in stored procedure.
The problem was that MySQL used unnecessarily large amounts of
memory if user variables were used as an argument to CONCAT or
CONCAT_WS -- 16M per each user variable used.
Technically, it happened because MySQL used the following
allocation strategy for string functions to avoid multiple
realloc() calls: in the virtual operation fix_length_and_dec()
the attribute max_length was calculated as a sum of max_length
values for each argument.
Although this approach worked well for small (or fixed) data types,
there could be a problem if there as a user variable among
the arguments of a string function -- max_length of the function
would be 16M (as the max_length of a user variable is 16M).
Both CONCAT() and CONCAT_WS() functions suffer from this problem.
The fix is to do not use meta-data for allocating memory.
The following strategy is proposed instead: allocate the exact
length of the result string at the first record, double the amount
of memory allocated when it is required.
No test case for this bug because there is no way to test memory
consumption in a robust way with our test suite.
The fix for bug 31148 is not correct. It does not
have a relation to the problem described in this bug.
And removing the fix will not make the bug to re-appear.
Fixed the bug #31974 by removing the fix for bug 31148
and adding a test case.
error evaluating WHERE"
DELETE with a subquery in WHERE clause would sometimes ignore subquery
evaluation error and proceed with deletion.
The fix is to check for an error after evaluation of the WHERE clause
in DELETE.
Addressed review comments.
If a stored function that contains a drop temporary table statement
is invoked by a create temporary table of the same name may cause
a server crash. The problem is that when dropping a table no check
is done to ensure that table is not being used by some outer query
(or outer statement), potentially leaving the outer query with a
reference to a stale (freed) table.
The solution is when dropping a temporary table, always check if
the table is being used by some outer statement as a temporary
table can be dropped inside stored procedures.
The check is performed by looking at the TABLE::query_id value for
temporary tables. To simplify this check and to solve a bug related
to handling of temporary tables in prelocked mode, this patch changes
the way in which this member is used to track the fact that table is
used/unused. Now we ensure that TABLE::query_id is zero for unused
temporary tables (which means that all temporary tables which were
used by a statement should be marked as free for reuse after it's
execution has been completed).
The mysql_change_user command fails to properly update the database pointer
when no database is selected, leading to "use after free" errors. The same
happens on the user privilege pointer in the thread security context.
The solution is to properly reset and update the database name. Also update
the user_priv pointer so that it doesn't point to freed memory.
during udf initialization. The bug is spotted while working on Bug 12713.
If a user-defined function was used in a SELECT statement, and an
error would occur during UDF initialization, this error would not terminate
execution of the SELECT, but rather would be converted to a warning.
The fix is to use a stack buffer to store the message from udf_init instead
of private my_error() buffer.
check_user()/check_connection()/check_for_max_user_connections().
This is a pre-requisite patch for the fix for Bug#12713 "Error in a stored
function called from a SELECT doesn't cause ROLLBACK of statem"
Implement review comments.
No functionality added or changed.
This is a pre-requisite for the fix for Bug#12713 Error in a stored
function called from a SELECT doesn't cause ROLLBACK of statem
Address post-review comments.
Dropping users causes huge increase in memory usage because field values were
allocated on the server memory root for temporary usage but never deallocated.
This patch changes the target memory root to be that of the thread handler
instead since this root is cleared between each statement.
