Introduced val_time_packed and val_datetime_packed functions for Item_direct_ref
to make sure to get the value from the item it is referring to.
The issue for incorrect result was that the item was getting its value
from the temporary table rather than from the view.
A bogus error message was issued when a condition was pushed into a
materialized derived table or view specified as union of selects with
aggregation when the corresponding columns of the selects had different
names. This happened because the expression pushed into having clauses of
the selects was adjusted for the names of the first select of the union.
The easiest solution was to rename the columns of the other selects to be
name compatible with the columns of the first select.
Approved by Oleksandr Byelkin <sanja@mariadb.com>
fix printing precedence for BETWEEN, LIKE/ESCAPE, REGEXP, IN
don't use precedence for printing CASE/WHEN/THEN/ELSE/END
fix parsing precedence of BETWEEN, LIKE/ESCAPE, REGEXP, IN
support predicate arguments for IN, BETWEEN, SOUNDS LIKE, LIKE/ESCAPE,
REGEXP
use %nonassoc for unary operators
fix parsing of IS TRUE/FALSE/UNKNOWN/NULL
remove parser_precedence test as superseded by the precedence test
Problem:
Queries like this showed performance degratation in 10.4 over 10.3:
SELECT temporal_literal FROM t1;
SELECT temporal_literal + 1 FROM t1;
SELECT COUNT(*) FROM t1 WHERE temporal_column = temporal_literal;
SELECT COUNT(*) FROM t1 WHERE temporal_column = string_literal;
Fix:
Replacing the universal member "MYSQL_TIME cached_time" in
Item_temporal_literal to data type specific containers:
- Date in Item_date_literal
- Time in Item_time_literal
- Datetime in Item_datetime_literal
This restores the performance, and make it even better in some cases.
See benchmark results in MDEV.
Also, this change makes futher separations of Date, Time, Datetime
from each other, which will make it possible not to derive them from
a too heavy (40 bytes) MYSQL_TIME, and replace them to smaller data
type specific containers.
Implementing methods:
- Field::val_time_packed()
- Field::val_datetime_packed()
- Item_field::val_datetime_packed(THD *thd);
- Item_field::val_time_packed(THD *thd);
to give a faster access to temporal packed longlong representation of a Field,
which is used in temporal Arg_comparator's to DATE, TIME, DATETIME data types.
The same idea is used in MySQL-5.6+.
This improves performance.
Problem:
When calculatung MIN() and MAX() in a query with GROUP BY, like this:
SELECT MIN(time_expr), MAX(time_expr) FROM t1 GROUP BY i;
the code in Item_sum_min_max::update_field() erroneosly used
string format comparison, therefore '100:20:30' was considered as
smaller than '10:20:30'.
Fix:
1. Implementing low level "native" related methods in class Time:
Time::Time(const Native &native) - convert native to Time
Time::to_native(Native *to, uint decimals) - convert Time to native
The "native" binary representation for TIME is equal to
the binary data format of Field_timef, which is used to
store TIME when mysql56_temporal_format is ON (default).
2. Implementing Type_handler_time_common "native" related methods:
Type_handler_time_common::cmp_native()
Type_handler_time_common::Item_val_native_with_conversion()
Type_handler_time_common::Item_val_native_with_conversion_result()
Type_handler_time_common::Item_param_val_native()
3. Implementing missing "native representation" related methods
in Field_time and Field_timef:
Field_time::store_native()
Field_time::val_native()
Field_timef::store_native()
Field_timef::val_native()
4. Implementing missing "native" related methods in all Items
that can have the TIME data type:
Item_timefunc::val_native()
Item_name_const::val_native()
Item_time_literal::val_native()
Item_cache_time::val_native()
Item_handled_func::val_native()
5. Marking Type_handler_time_common as "native ready".
So now Item_sum_min_max::update_field() calculates
values using min_max_update_native_field(),
which uses native binary representation rather than string representation.
Before this change, only the TIMESTAMP data type used native
representation to calculate MIN() and MAX().
Benchmarks (see more details in MDEV):
This change not only fixes the wrong result, but also
makes a "SELECT .. MAX.. GROUP BY .." query faster:
# TIME(0)
CREATE TABLE t1 (id INT, time_col TIME) ENGINE=HEAP;
INSERT INTO t1 VALUES (1,'10:10:10'); -- repeat this 1m times
SELECT id, MAX(time_col) FROM t1 GROUP BY id;
MySQL80: 0.159 sec
10.3: 0.108 sec
10.4: 0.094 sec (fixed)
# TIME(6):
CREATE TABLE t1 (id INT, time_col TIME(6)) ENGINE=HEAP;
INSERT INTO t1 VALUES (1,'10:10:10.999999'); -- repeat this 1m times
SELECT id, MAX(time_col) FROM t1 GROUP BY id;
My80: 0.154
10.3: 0.135
10.4: 0.093 (fixed)
Item_cache_datetime::decimals was always copied from example->decimals
without limiting to 6 (maximum possible fractional digits), so
val_str() later crashed on asserts inside my_time_to_str() and
my_datetime_to_str().
Item_default_value did not override val_native(), so the inherited
Item_field::val_native() was called. As a result Item_default_value::calculate()
was not called and Item_field::val_native() was called on a Field
with a non-initialized ptr.
Implementing Item_default_value::val_native() properly.
Item_null_result did not override type_handler() because of a wrong merge
of d8a9b524f2 (MDEV-14221) from 10.1.
Overriding type_handler().
Removing the old style field_type() method. It's not relevant any more.
Problem:
When handling a query like this:
VALUES ('') UNION SELECT _utf16 0x0020 COLLATE utf16_bin;
Type_handler_string_result::Item_hybrid_func_fix_attributes()
tried to apply character set conversion Item_type_holder,
which causes a crash on DBUG_ASSERT(0) inside Item_type_holder::val_str().
Fix:
Overriding Item_type_holder's methods to avoid this, as follows:
bool const_item() const { return false; }
bool is_expensive() { return true; }
Removing a wrong DBUG_ASSERT:
When Item_param gets "unfixed" in cleanup(), its "fixed" gets assigned
to false, while item_item keeps the value. So the assert was wrong.
Perhaps, instead of removing the assert, it was possible to reset
item_type to NO_VALUE in cleanup. But this is not very important:
it's implemented in 10.4 in a better way:
Item_param::is_fixed() always returns true and it does not need to be "unfixed".
1. Code simplification:
Item_default_value handled all these values:
a. DEFAULT(field)
b. DEFAULT
c. IGNORE
and had various conditions to distinguish (a) from (b) and from (c).
Introducing a new abstract class Item_contextually_typed_value_specification,
to handle (b) and (c), so the hierarchy now looks as follows:
Item
Item_result_field
Item_ident
Item_field
Item_default_value - DEFAULT(field)
Item_contextually_typed_value_specification
Item_default_specification - DEFAULT
Item_ignore_specification - IGNORE
2. Introducing a new virtual method is_evaluable_expression() to
determine if an Item is:
- a normal expression, so its val_xxx()/get_date() methods can be called
- or a just an expression substitute, whose value methods cannot be called.
3. Disallowing Items that are not evalualble expressions in table value
constructors.
The code erroneously allowed both:
INSERT INTO t1 (vcol) VALUES (DEFAULT);
INSERT INTO t1 (vcol) VALUES (DEFAULT(non_virtual_column));
The former is OK, but the latter is not.
Adding a new virtual method in Item:
virtual bool vcol_assignment_allowed_value() const { return false; }
Item_null, Item_param and Item_default_value override it.
Item_default_value overrides it in the way to:
- allow DEFAULT
- disallow DEFAULT(col)
Same array instance in two Item_func_in instances. First Item_func_in
instance is freed on table close. Second one is freed on
cleanup_after_query().
get_copy() depends on copy ctor for copying an item and hence does
shallow copy for default copy ctor. Use build_clone() for deep copy of
Item_func_in.
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.
Item_ref::val_(datetime|time)_packed() erroneously called
(*ref)->val_(datetime|time)_packed().
- Fixing to call (*ref)->val_(datetime|time)_packed_result().
- Backporting Item::val_(datetime|time)_packed_result() from 10.3.
- Fixing Item_field::get_date_result() to handle null_value in the same
way how Item_field::get_date() does.
This change takes into account a column's GENERATED ALWAYS AS
expression dependcy on sql_mode's PAD_CHAR_TO_FULL_LENGTH and
NO_UNSIGNED_SUBTRACTION flags.
Indexed virtual columns as well as persistent generated columns are
now not allowed to have such dependencies to avoid inconsistent data
or index files on sql_mode changes.
So an error is now returned in cases like this:
CREATE OR REPLACE TABLE t1
(
a CHAR(5),
v VARCHAR(5) AS (a) PERSISTENT -- CHAR->VARCHAR or CHAR->TEXT = ERROR
);
Functions RPAD() and RTRIM() can now remove dependency on
PAD_CHAR_TO_FULL_LENGTH. So this can be used instead:
CREATE OR REPLACE TABLE t1
(
a CHAR(5),
v VARCHAR(5) AS (RTRIM(a)) PERSISTENT
);
Note, unlike CHAR->VARCHAR and CHAR->TEXT this still works,
not RPAD(a) is needed:
CREATE OR REPLACE TABLE t1
(
a CHAR(5),
v CHAR(5) AS (a) PERSISTENT -- CHAR->CHAR is OK
);
More sql_mode flags may affect values of generated columns.
They will be addressed separately.
See comments in sql_mode.h for implementation details.
