The parser is allocating Item_field for references by name in ORDER BY
expressions. Such expressions however may point not only to Item_field
in the select list (or to a table column) but also to an arbitrary Item.
This causes Item_field::fix_fields to throw an error about missing
column.
The fix substitutes Item_field for the reference with an Item_ref when
not pointing to Item_field.
This is a performance issue for queries with subqueries evaluation
of which requires filesort.
Allocation of memory for the sort buffer at each evaluation of a
subquery may take a significant amount of time if the buffer is rather big.
With the fix we allocate the buffer at the first evaluation of the
subquery and reuse it at each subsequent evaluation.
Evaluate "NULL IN (SELECT ...)" in a special way: Disable pushed-down
conditions and their "consequences":
= Do full table scans instead of unique_[index_subquery] lookups.
= Change appropriate "ref_or_null" accesses to full table scans in
subquery's joins.
Also cache value of NULL IN (SELECT ...) if the SELECT is not correlated
wrt any upper select.
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.
select OK.
The SQL parser was using Item::name to transfer user defined function attributes
to the user defined function (udf). It was not distinguishing between user defined
function call arguments and stored procedure call arguments. Setting Item::name
was causing Item_ref::print() method to print the argument as quoted identifiers
and caused views that reference aggregate functions as udf call arguments (and
rely on Item::print() for the text of the view to store) to throw an undefined
identifier error.
Overloaded Item_ref::print to print aggregate functions as such when printing
the references to aggregate functions taken out of context by split_sum_func2()
Fixed the parser to properly detect using AS clause in stored procedure arguments
as an error.
Fixed printing the arguments of udf call to print properly the udf attribute.
If elements a not top-level IN subquery were accessed by an index and
the subquery result set included a NULL value then the quantified
predicate that contained the subquery was evaluated to NULL when
it should return a non-null value.
Backport from 5.1.
Raised STACK_MIN_SIZE for Debian GNU/Linux Sid,
Linux kernel 2.6.16,
gcc version 3.3.6 (Debian 1:3.3.6-13),
libc6-dbg 2.3.6.ds1-4,
Pentium4 (x86),
BUILD/compile-pentium-debug-max
Raised about 100 Bytes above the required minimum.
