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Condition can be pushed from the HAVING clause into the WHERE clause
if it depends only on the fields that are used in the GROUP BY list
or depends on the fields that are equal to grouping fields.
Aggregate functions can't be pushed down.
How the pushdown is performed on the example:
SELECT t1.a,MAX(t1.b)
FROM t1
GROUP BY t1.a
HAVING (t1.a>2) AND (MAX(c)>12);
=>
SELECT t1.a,MAX(t1.b)
FROM t1
WHERE (t1.a>2)
GROUP BY t1.a
HAVING (MAX(c)>12);
The implementation scheme:
1. Extract the most restrictive condition cond from the HAVING clause of
the select that depends only on the fields that are used in the GROUP BY
list of the select (directly or indirectly through equalities)
2. Save cond as a condition that can be pushed into the WHERE clause
of the select
3. Remove cond from the HAVING clause if it is possible
The optimization is implemented in the function
st_select_lex::pushdown_from_having_into_where().
New test file having_cond_pushdown.test is created.
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time type
MDEV-17625 Different warnings when comparing a garbage to DATETIME vs TIME
- Splitting processes of data type conversion (to TIME/DATE,DATETIME)
and warning generation.
Warning are now only get collected during conversion (in an "int" variable),
and are pushed in the very end of conversion (not in parallel).
Warnings generated by the low level routines str_to_xxx() and number_to_xxx()
can now be changed at the end, when TIME_FUZZY_DATES is applied,
from "Invalid value" to "Truncated invalid value".
Now "Illegal value" is issued only when the low level routine returned
an error and TIME_FUZZY_DATES was not set. Otherwise, if the low level
routine returned "false" (success), or if NULL was converted to a zero
datetime by TIME_FUZZY_DATES, then "Truncated illegal value"
is issued. This gives better warnings.
- Methods Type_handler::Item_get_date() and
Type_handler::Item_func_hybrid_field_type_get_date() now only
convert and collect warning information, but do not push warnings.
- Changing the return data type for Type_handler::Item_get_date()
and Type_handler::Item_func_hybrid_field_type_get_date() from
"bool" to "void". The conversion result (success vs error) can be
checked by testing ltime->time_type. MYSQL_TIME_{NONE|ERROR}
mean mean error, other values mean success.
- Adding new wrapper methods Type_handler::Item_get_date_with_warn() and
Type_handler::Item_func_hybrid_field_type_get_date_with_warn()
to do conversion followed by raising warnings, and changing
the code to call new Type_handler::***_with_warn() methods.
- Adding a helper class Temporal::Status, a wrapper
for MYSQL_TIME_STATUS with automatic initialization.
- Adding a helper class Temporal::Warn, to collect warnings
but without actually raising them. Moving a part of ErrConv
into a separate class ErrBuff, and deriving both Temporal::Warn
and ErrConv from ErrBuff. The ErrBuff part of Temporal::Warn
is used to collect textual representation of the input data.
- Adding a helper class Temporal::Warn_push. It's used
to collect warning information during conversion, and
automatically pushes warnings to the diagnostics area
on its destructor time (in case of non-zero warning).
- Moving more code from various functions inside class Temporal.
- Adding more Temporal_hybrid constructors and
protected Temporal methods make_from_xxx(),
which convert and only collect warning information, but do not
actually raise warnings.
- Now the low level functions str_to_datetime() and str_to_time()
always set status->warning if the return value is "true" (error).
- Now the low level functions number_to_time() and number_to_datetime()
set the "*was_cut" argument if the return value is "true" (error).
- Adding a few DBUG_ASSERTs to make sure that str_to_xxx() and
number_to_xxx() always set warnings on error.
- Adding new warning flags MYSQL_TIME_WARN_EDOM and MYSQL_TIME_WARN_ZERO_DATE
for the code symmetry. Before this change there was a special
code path for (rc==true && was_cut==0) which was treated by
Field_temporal::store_invalid_with_warning as "zero date violation".
Now was_cut==0 always means that there are no any error/warnings/notes
to be raised, not matter what rc is.
- Using new Temporal_hybrid constructors in combination with
Temporal::Warn_push inside str_to_datetime_with_warn(),
double_to_datetime_with_warn(), int_to_datetime_with_warn(),
Field::get_date(), Item::get_date_from_string(), and a few other places.
- Removing methods Dec_ptr::to_datetime_with_warn(),
Year::to_time_with_warn(), my_decimal::to_datetime_with_warn(),
Dec_ptr::to_datetime_with_warn().
Fixing Sec6::to_time() and Sec6::to_datetime() to
convert and only collect warnings, without raising warnings.
Now warning raising functionality resides in Temporal::Warn_push.
- Adding classes Longlong_hybrid_null and Double_null, to
return both value and the "IS NULL" flag. Adding methods
Item::to_double_null(), to_longlong_hybrid_null(),
Item_func_hybrid_field_type::to_longlong_hybrid_null_op(),
Item_func_hybrid_field_type::to_double_null_op().
Removing separate classes VInt and VInt_op, as they
have been replaced by a single class Longlong_hybrid_null.
- Adding a helper method Temporal::type_name_by_timestamp_type(),
moving a part of make_truncated_value_warning() into it,
and reusing in Temporal::Warn::push_conversion_warnings().
- Removing Item::make_zero_date() and
Item_func_hybrid_field_type::make_zero_mysql_time().
They provided duplicate functionality.
Now this code resides in Temporal::make_fuzzy_date().
The latter is now called for all Item types when data type
conversion (to DATE/TIME/DATETIME) is involved, including
Item_field and Item_direct_view_ref.
This fixes MDEV-17563: Item_direct_view_ref now correctly converts
NULL to a zero date when TIME_FUZZY_DATES says so.
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