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.
When implicitly converting string fields to numbers the
string-to-number conversion error was not sent to the client.
Added code to send the conversion error as warning.
We also need to prevent generation of warnings from the places
where val_xxx() methods are called for the sole purpose of updating
the Item::null_value flag.
To achieve that a special function is added (and called) :
update_null_value(). This function will set the no_errors flag and
will call val_xxx(). The warning generation in Field_string::val_xxx()
will use the flag when generating the conversion warnings.
expression cols.
The problem was that MYSQL_FIELD::org_name was set for MIN() and MAX()
functions (COUNT() is also mentioned in the bug report but was already
fixed).
After this patch for expressions MYSQL_FIELD::name is set to either
expression itself or its alias, and other data origin fields of
MYSQL_FILED (db, org_table, table, org_name) are empty strings.
Moved .progress files into the log directory
Moved 'cluster' database tables into the MySQL database, to not have 'cluster' beeing a reserved database name
Fixed bug where mysqld got a core dump when trying to use a table created by MySQL 3.23
Fixed some compiler warnings
Fixed small memory leak in libmysql
Note that this doesn't changeset doesn't include the new mysqldump.c code required to run some tests. This will be added when I merge 5.0 to 5.1
Problem: GROUP_CONCAT on a multi-byte column can truncate
in the middle of a multibyte character when applying
group_concat_max_len limit. It produces an invalid
multi-byte character in the result string.
The second, easier version - reusing old "warning_for_row" flag,
instead of introducing of "result_is_full" - which was
added in the previous commit.
Item::val_xxx() may be called by the server several times at execute time
for a single query. Calls to val_xxx() may be very expensive and sometimes
(count(distinct), sum(distinct), avg(distinct)) not possible.
To avoid that problem the results of calculation for these aggregate
functions are cached so that val_xxx() methods just return the calculated
value for the second and subsequent calls.
(COUNT(*) = 1) not working in SELECT inside prepared statement.
Note: the warning was introduced in 5.0 and 5.1, 4.1 is OK with the
original fix.
The problem was that in 5.0 and 5.1 clear() for group functions may
access hybrid_type member, and this member is initialized in
fix_fields().
So we should not call clear() from item cleanup() methods, as cleanup()
may be called for unfixed items.
statement.
The problem was that during statement re-execution if the result was
empty the old result could be returned for group functions.
The solution is to implement proper cleanup() method in group
functions.
post-review fixes as indicated by Serg.
manual testing of error cases done in 5.0 due to support for DBUG_EXECUTE_IF
to insert errors.
Unable to write test case for mysql-test until 5.1 due to support for setting
debug options at runtime.
