UNIQUE (eq-ref) lookups result in table being considered as a "constant" table.
Queries that consist of only constant tables are processed in do_select() in a
special way that doesn't invoke evaluate_join_record(), and therefore doesn't
increase the counters join->examined_rows and join->thd->row_count.
The patch increases these counters in this special case.
NOTICE:
This behavior seems to contradict what the documentation says in Sect. 5.11.4:
"Queries handled by the query cache are not added to the slow query log, nor
are queries that would not benefit from the presence of an index because the
table has zero rows or one row."
No test case in 5.0 as issue shows only in slow query log, and other counters
can give subtly different values (with regard to counting in create_sort_index(),
synthetic rows in ROLLUP, etc.).
There are two problems with ROUND(X, D) on an exact numeric
(DECIMAL, NUMERIC type) field of a table:
1) The implementation of the ROUND function would change the number of decimal
places regardless of the value decided upon in fix_length_and_dec. When the
number of decimal places is not constant, this would cause an inconsistent
state where the number of digits was less than the number of decimal places,
which crashes filesort.
Fixed by not allowing the ROUND operation to add any more decimal places than
was decided in fix_length_and_dec.
2) fix_length_and_dec would allow the number of decimals to be greater than
the maximium configured value for constant values of D. This led to the same
crash as in (1).
Fixed by not allowing the above in fix_length_and_dec.
The fix is a copy of Martin Friebe's suggestion.
added testing for no_appended which will be false if anything,
including the empty string is in result
SHOW FIELDS FROM a view with no valid definer was possible (since fix
for Bug#26817), but gave NULL as a field-type. This led to mysqldump-ing
of such views being successful, but loading such a dump with the client
failing. Patch allows SHOW FIELDS to give data-type of field in underlying
table.
doesn't recognize it
This is a 5.1 version of the patch.
Problem:
'log' and 'log_slow_queries' were "fixed" variables, i.e. they showed up
in SHOW VARIABLES, but could not be used in expressions like
"select @@log". Also, using them in the SET statement produced an
incorrect "unknown system variable" error.
Solution:
Since as of MySQL 5.1.12 one can enable or disable the general query log
or the slow query log at runtime by changing values of
general_log/slow_query_log, make 'log' and 'log_slow_queries" to be
synonyms for 'general_log' and 'slow_query_log' respectively. This
makes expressions using the '@@var' syntax backward compatible with
5.0 and SHOW VARIABLES output to be consistent with the SET statement.
doesn't recognize it
This is a 5.0 version of the patch, it will be null-merged to 5.1
Problem:
'log' and 'log_slow_queries' were "fixed" variables, i.e. they showed up
in SHOW VARIABLES, but could not be used in expressions like
"select @@log". Also, using them in the SET statement produced an
incorrect "unknown system variable" error.
Solution:
Make 'log' and 'log_slow_queries' read-only dynamic variables to make
them available for use in expressions, and produce a correct error
about the variable being read-only when used in the SET statement.
all space column names.
The parser has been modified to check VIEW column names
with the check_column_name function and to report an error
on empty and all space column names (same as for TABLE
column names).
file .\opt_sum.cc, line
The optimizer pre-calculates the MIN/MAX values for queries like
SELECT MIN(kp_k) WHERE kp_1 = const AND ... AND kp_k-1 = const
when there is a key over kp_1...kp_k
In doing so it was not checking correctly nullability and
there was a superfluous assert().
Fixed by making sure that the field can be null before checking and
taking out the wrong assert().
.
Introduced a correct check for nullability
The MIN(field) can return NULL when all the row values in the group
are NULL-able or if there were no rows.
Fixed the assertion to reflect the case when there are no rows.
