The optimizer removes expressions from GROUP BY/DISTINCT
if they happen to participate in a <expression> = <const>
predicates of the WHERE clause (the idea being that if
it's always equal to a constant it can't have multiple
values).
However for predicates where the expression and the
constant item are of different result type this is not
valid (e.g. a string column compared to 0).
Fixed by additional check of the result types of the
expression and the constant and if they differ the
expression don't get removed from the group by list.
This bug appeared after the patch for bug 21390 that had added some code
to handle outer joins with no matches after substitution of a const
table in an efficient way. That code as it is cannot be applied to the case
of nested outer join operations. Being applied to the queries with
nested outer joins the code can cause crashes or wrong result sets.
The fix blocks row substitution for const inner tables of an outer join
if the inner operand is not a single table.
With MySQL 3.23 and 4.0, the syntax 'LIMIT N, -1' is accepted, and returns
all the rows located after row N. This behavior, however, is not the
intended result, and defeats the purpose of LIMIT, which is to constrain
the size of a result set.
With MySQL 4.1 and later, this construct is correctly detected as a syntax
error.
This fix does not change the production code, and only adds a new test case
to improve test coverage in this area, to enforce in the test suite the
intended behavior.
repair it
Multi-table delete that is optimized with QUICK_RANGE reports table
corruption.
DELETE statement must not use KEYREAD optimization, and sets
table->no_keyread to 1. This was ignored in QUICK_RANGE optimization.
With this fix QUICK_RANGE optimization honors table->no_keyread
value and does not enable KEYREAD when it is requested.
When only one row was present, the subtraction of nearly the same number
resulted in catastropic cancellation, introducing an error in the
VARIANCE calculation near 1e-15. That was sqrt()ed to get STDDEV, the
error was escallated to near 1e-8.
The simple fix of testing for a row count of 1 and forcing that to yield
0.0 is insufficient, as two rows of the same value should also have a
variance of 0.0, yet the error would be about the same.
So, this patch changes the formula that computes the VARIANCE to be one
that is not subject to catastrophic cancellation.
In addition, it now uses only (faster-than-decimal) floating point numbers
to calculate, and renders that to other types on demand.
Handling of large signed/unsigned values was not consistent, so some string functions could return bogus results.
The current fix is to simply patch up the val_str() methods for those string items.
It would be good clean this code up in general, to make similar problems much harder to make. This is left as an exercise for the reader.
spatial index
While executing OPTIMIZE TABLE on MyISAM tables the server re-creates the
index file(s) in order to sort them physically by the key. This cannot be
done for R-tree indexes as it makes no sense.
The server was not checking the type of the index and was accessing an
R-tree index as if it was a B-tree.
Fixed by preventing sorting the index file if it contains an R-tree index.
If SELECT-part of CREATE VIEW statement contains '\Z',
it is not handled correctly.
The problem was in String::print().
Symbol with code 032 (26) is replaced with '\z',
which is not supported by the lexer.
The fix is to replace the symbol with '\Z'.
the UDF
When deleting a user defined function MySQL must remove it from both the
in-memory hash table and the mysql.proc system table.
Finding (and removal therefore) from the internal hash table is case
insensitive (or whatever the default charset is), whereas finding and
removal from the system table is case sensitive.
As a result if you supply a function name that is not in the same character
case to DROP FUNCTION the server will remove the function only from the
in-memory hash table and will keep the row in mysql.proc system table.
This will cause inconsistency between the two structures (that is fixed
only by restarting the server).
Fixed by using the name in the precise case (from the in-memory hash table)
to delete the row in the mysql.proc system table.
Problem:
When creating a temporary field for a temporary table in create_tmp_field_from_field(), a resulting field is created as an exact copy of an original one (in Field::new_field()). However, Field_enum and Field_set contain a pointer (typelib) to memory allocated in the parent table's MEM_ROOT, which under some circumstances may be deallocated later by the time a temporary table is used.
Solution:
Override the new_field() method for Field_enum and Field_set and create a separate copy of the typelib structure in there.
- When this bug was corrected it changed the behavior
for data/index directory in the myisam test case.
- This patch moves the OS depending tests to a non-windows
test file.
Blocked evaluation of constant objects of the classes
Item_func_is_null and Item_is_not_null_test at the
prepare phase in the cases when the objects used subqueries.
Removed an assertion that was not valid for the cases where the query
in a prepared statement contained a single-row non-correlated
subquery that was used as an argument of the IS NULL predicate.
Bug#4968 "Stored procedure crash if cursor opened on altered table"
Bug#19733 "Repeated alter, or repeated create/drop, fails"
Bug#19182 "CREATE TABLE bar (m INT) SELECT n FROM foo; doesn't work from
stored procedure."
Bug#6895 "Prepared Statements: ALTER TABLE DROP COLUMN does nothing"
Bug#22060 "ALTER TABLE x AUTO_INCREMENT=y in SP crashes server"
Test cases for bugs 4968, 19733, 6895 will be added in 5.0.
Re-execution of CREATE DATABASE, CREATE TABLE and ALTER TABLE
statements in stored routines or as prepared statements caused
incorrect results (and crashes in versions prior to 5.0.25).
In 5.1 the problem occured only for CREATE DATABASE, CREATE TABLE
SELECT and CREATE TABLE with INDEX/DATA DIRECTOY options).
The problem of bugs 4968, 19733, 19282 and 6895 was that functions
mysql_prepare_table, mysql_create_table and mysql_alter_table were not
re-execution friendly: during their operation they used to modify contents
of LEX (members create_info, alter_info, key_list, create_list),
thus making the LEX unusable for the next execution.
In particular, these functions removed processed columns and keys from
create_list, key_list and drop_list. Search the code in sql_table.cc
for drop_it.remove() and similar patterns to find evidence.
The fix is to supply to these functions a usable copy of each of the
above structures at every re-execution of an SQL statement.
To simplify memory management, LEX::key_list and LEX::create_list
were added to LEX::alter_info, a fresh copy of which is created for
every execution.
The problem of crashing bug 22060 stemmed from the fact that the above
metnioned functions were not only modifying HA_CREATE_INFO structure in
LEX, but also were changing it to point to areas in volatile memory of
the execution memory root.
The patch solves this problem by creating and using an on-stack
copy of HA_CREATE_INFO (note that code in 5.1 already creates and
uses a copy of this structure in mysql_create_table()/alter_table(),
but this approach didn't work well for CREATE TABLE SELECT statement).
