with condition_pushdown_from_having
This bug could manifest itself for queries with GROUP BY and HAVING clauses
when the HAVING clause was a conjunctive condition that depended
exclusively on grouping fields and at least one conjunct contained an
equality of the form fld=sq where fld is a grouping field and sq is a
constant subquery.
In this case the optimizer tries to perform a pushdown of the HAVING
condition into WHERE. To construct the pushable condition the optimizer
first transforms all multiple equalities in HAVING into simple equalities.
This has to be done for a proper processing of the pushed conditions
in WHERE. The multiple equalities at all AND/OR levels must be converted
to simple equalities because any multiple equality may refer to a multiple
equality at the upper level.
Before this patch the conversion was performed like this:
multiple_equality(x,f1,...,fn) => x=f1 and ... and x=fn.
When an equality item for x=fi was constructed both the items for x and fi
were cloned. If x happened to be a constant subquery that could not be
cloned the conversion failed. If the conversions of multiple equalities
previously performed had succeeded then the whole condition became in an
inconsistent state that could cause different failures.
The solution provided by the patch is:
1. to use a different conversion rule if x is a constant
multiple_equality(x,f1,...,fn) => f1=x and f2=f1 and ... and fn=f1
2. not to clone x if it's a constant.
Such conversions cannot fail and besides the result of the conversion
preserves the equivalence of f1,...,fn that can be used for other
optimizations.
This patch also made sure that expensive predicates are not pushed from
HAVING to WHERE.
(Variant #2 of the patch, which keeps the sp_head object inside the
MEM_ROOT that sp_head object owns)
(10.3 version of the fix, with handling for class sp_package)
sp_head::operator new() and operator delete() were dereferencing sp_head*
pointers to memory that didn't hold a valid sp_head object (it was
not created/already destroyed).
This caused UBSan to crash when looking up type information.
Fixed by providing static sp_head::create() and sp_head::destroy() methods.
Set read_set bitmap for view from the JOIN::all_fields list instead of JOIN::fields_list
as split_sum_func would have added items to the all_fields list.
LEX::parsed_select_expr_cont(): Replace a condition with an
assertion DBUG_ASSERT(!s2->next_select()), and always
initialize sel1=s2, because all subsequent code paths will
assign to sel1->first_nested.
This was flagged by GCC reporting -Wmaybe-uninitialized
for the statement last->link_neighbour(sel1).
Shift-Reduce conflicts prevented parsing some queries with subqueries that
used set operations when the subqueries occurred in expressions or in IN
predicands.
The grammar rules for query expression were transformed in order to avoid
these conflicts. New grammar rules employ an idea taken from MySQL 8.0.
Pruning fix for SYSTEM_TIME INTERVAL partitioning.
Allocating one more element in range_int_array for CURRENT partition
is required for RANGE pruning to work correctly
(get_partition_id_range_for_endpoint()).
SYSTEM_TYPE partitioning: COLUMN properties removed. Partitioning is
now pure RANGE based on UNIX_TIMESTAMP(row_end).
DECIMAL type is now allowed as RANGE partitioning, we can partition by
UNIX_TIMESTAMP() (but not for DATETIME which depends on local timezone
of course).
With --skip-debug-assert, DBUG_ASSERT(false) will allow execution to
continue. Hence, we will need /* fall through */ after them.
Some DBUG_ASSERT(0) were replaced by break; when the switch () statement
was followed by DBUG_ASSERT(0).
- Initialize variables that could be used uninitialized
- Added extra end space to DbugStringItemTypeValue to get rid of warnings
from c_ptr()
- Session_sysvars_tracker::update() accessed unitialized memory if called
with NULL value.
- get_schema_stat_record() accessed unitialized memory if HA_KEY_LONG_HASH
was used
- parse_vcol_defs() accessed random memory for tables without keys.
cmake -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_BUILD_TYPE=Debug
Maintainer mode makes all warnings errors. This patch fix warnings. Mostly about
deprecated `register` keyword.
Too much warnings came from Mroonga and I gave up on it.
This patch complements the patch that fixes bug MDEV-18479.
This patch takes care of possible overflow when calculating the
estimated number of rows in a materialized derived table / view.
query with VALUES()
A table value constructor can be used in all contexts where a select
can be used. In particular an ORDER BY clause or a LIMIT clause or both
of them can be attached to a table value constructor to produce a new
query. Unfortunately execution of such queries was not supported.
This patch fixes the problem.
Only take LOCK_plugin for plugin system variables.
Reverted optimisation that was originally done for session tracker: it
makes much less sense now. Specifically only if connections would want to
track plugin session variables changes and these changes would actually
happen frequently. If this ever becomes an issue, there're much better
ways to optimise this workload.
Part of MDEV-14984 - regression in connect performance
This patch corrects the patch for MDEV-19324. The latter did not
work properly in the cases when the transformation
(SELECT ... ORDER BY ...) LIMIT ... =>
SELECT ... ORDER BY ... LIMIT ...
was applied to the operands of a set operation.
If a select query was of the form (SELECT ... ORDER BY ...) LIMIT ...
then in most cases it returned incorrect result. It happened because
SELECT ... ORDER BY ... was wrapped into a select with materialized
derived table:
SELECT ... ORDER BY ... =>
SELECT * FROM (SELECT ... ORDER BY ...) dt.
Yet for any materialized derived table ORDER BY without LIMIT is ignored.
This patch resolves the problem by the conversion
(SELECT ... ORDER BY ...) LIMIT ... =>
SELECT ... ORDER BY ... LIMIT ...
at the parser stage.
Similarly
((SELECT ... UNION ...) ORDER BY ...) LIMIT ...
is converted to
(SELECT ... UNION ...) ORDER BY ... LIMIT ...
This conversion optimizes execution of the query because the result of
(SELECT ... UNION ...) ORDER BY ... is not materialized into a temporary
table anymore.
A sequence of <digits>e<mbhead><mbtail>, e.g.:
SELECT 123eXYzzz FROM t1;
was not scanned correctly (where XY is a multi-byte character).
The multi-byte head byte X was appended to 123e separately from
the multi-byte tail byte Y, so a pointer to "Yzzz" was passed
into scan_ident_start(), which failed on a bad multi-byte sequence.
After this change, scan_ident_start() gets a pointer to "XYzzz",
so it correctly sees the whole multi-byte character.
When pushing a condition from HAVING into WHERE the function
st_select_lex::pushdown_from_having_into_where() transforms column
references in the pushed condition then performs cleanup of
items of the condition and finally calls fix_fields() for the condition
items. The cleanup is performed by a call of the method walk() with
cleanup_processor as the first parameter. Unfortunately this sequence
of calls does not work if the condition contains cached items, because
fix_fields() cannot go through Item_cache items and this leaves
underlying items unfixed.
The solution of this problem used in this patch is just does not allow
to process Item_cache objects when performing cleanup of the pushed
condition. In order to let the traversal procedure walk() not to process
Item_cache objects the third parameter of the used call of walk()
is set to a fictitious pointer (void *) 1. And Item_cache::walk() is
changed to prevent any action when it gets such value as the third
parameter.
