Treat queries with no FROM and aggregate functions as normal queries,
so the aggregate function get correctly calculated as if there is 1 row.
This means that they will be considered to have one row, so COUNT(*) will return
1 instead of 0. Other aggregates will behave in compatible manner.
The problem was in that opt_sum_query() replaced MIN/MAX functions
with the corresponding constant found in a key, but due to imprecise
representation of float numbers, when evaluating the where clause,
this comparison failed.
When MIN/MAX optimization detects that all tables can be removed,
also remove all conjuncts in a where clause that refer to these
tables. As a result of this fix, these conditions are not evaluated
twice, and in the case of float number comparisons we do not discard
result rows due to imprecise float representation.
As a side-effect this fix also corrects an unnoticed problem in
bug 12882.
The bug report revealed two problems related to min/max optimization:
1. If the length of a constant key used in a SARGable condition for
for the MIN/MAX fields is greater than the length of the field an
unwanted warning on key truncation is issued;
2. If MIN/MAX optimization is applied to a partial index, like INDEX(b(4))
than can lead to returning a wrong result set.
The problem was in that the MIN/MAX optimization in opt_sum_query was
replacing MIN/MAX functions with their constant argument without
taking into account that a query has no result rows.
Logging to logging@openlogging.org accepted
func_group.result, func_group.test:
Added a test case for bug #8893.
opt_sum.cc:
A misplaced initialization for the returned parameter
prefix_len in the function find_key_for_maxmin caused
usage of a wrong key prefix by the min/max optimization
in cases when the matching index was not the first index
that contained the min/max field.
Added more DBUG statements
Ensure that we are comparing end space with BINARY strings
Use 'any_db' instead of '' to mean any database. (For HANDLER command)
Only strip ' ' when comparing CHAR, not other space-like characters (like \t)
Cleaned up embedded library access and query cache handling
Changed min stack size to 128K (to allow longer MyISAM keys)
Fixed wrong priority for XOR (should be less than NEG to get -1^1 to work)
SQL_BIG_RESULT used": now BIT_AND() always returns 18446744073709551615
if no rows were found.
This patch also fixes bug #1972: "BIT_AND() and BIT_OR() still return
a *signed* 64bit value"
SQL_BIG_RESULT used':
- BIT_AND now returns BIGINT UNSIGNED
- in case there were no matching rows BIT_AND returns 18446744073709551615
(but not NULL), BIT_OR returns 0 (but not NULL). That's how Monty wants it
and how is described in our docs.
"BIT_AND() result in GROUP BY different when SQL_BIG_RESULT used"
return value of BIT_AND changed to BIGINT SIGNED
Also the patch fixes another bug: when temporary table is in use and one of
values in group is NULL, BIT_AND always returns zero.
Fixed it to always skip null values.
by MAX/MIN in some cases:
SELECT coercibility(max(s1)) from t1;
Subselect collation and derivation was not processed
correctly:
create table a select (select s1 from t1);
select * from t1 where s1 = (select s2 from t1);
Added new tests for better coverage of
min/max optimization code.
func_group.test:
Added new tests for better coverage of
min/max optimization code.
opt_sum.cc:
Fixed wrong previous manual merge.
Fixed bugs concerning fields used in min/max
functions for which there are conditions of
the form field=const.
Added ALL as parameter option for all group functions.
Make join handling uniform. This allows us to use ',', JOIN and INNER JOIN the same way.
Sort NULL last if DESC is used (ANSI SQL 99 requirement)
MIN(key_column) could in some cases return NULL on a column with NULL and other values.
MIN(key_column) and MAX(key_column) could in some cases return wrong values when used in OUTER JOIN.
