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/*
Copyright (c) 2023, MariaDB
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA */
#ifndef OPT_REWRITE_DATE_CMP_INCLUDED
#define OPT_REWRITE_DATE_CMP_INCLUDED
class Item_func_eq;
class Item_func_ge;
class Item_func_gt;
class Item_func_le;
class Item_func_lt;
class Item_bool_rowready_func2;
/*
@brief Class responsible for rewriting datetime comparison condition.
It rewrites non-sargable conditions into sargable.
@detail
The intent of this class is to do equivalent rewrites as follows:
YEAR(col) <= val -> col <= year_end(val)
YEAR(col) < val -> col < year_start(val)
YEAR(col) >= val -> col >= year_start(val)
YEAR(col) > val -> col > year_end(val)
YEAR(col) = val -> col >= year_start(val) AND col<=year_end(val)
Also the same is done for comparisons with DATE(col):
DATE(col) <= val -> col <= day_end(val)
if col has a DATE type (not DATETIME), then the rewrite becomes:
DATE(col) <= val -> col <= val
@usage
Date_cmp_func_rewriter rwr(thd, item_func);
Item *new_item= rwr.get_rewrite_result();
Returned new_item points to an item that item_func was rewritten to.
new_item already has fixed fields (fix_fields() was called).
If no rewrite happened, new_item points to the initial item_func parameter
@todo
Also handle conditions in form "YEAR(date_col) BETWEEN 2014 AND 2017"
and "YEAR(col) = c1 AND MONTH(col) = c2"
*/
class Date_cmp_func_rewriter
{
public:
Date_cmp_func_rewriter(THD* thd, Item_func_eq *item_func);
Date_cmp_func_rewriter(THD* thd, Item_func_ge *item_func);
Date_cmp_func_rewriter(THD* thd, Item_func_gt *item_func);
Date_cmp_func_rewriter(THD* thd, Item_func_le *item_func);
Date_cmp_func_rewriter(THD* thd, Item_func_lt *item_func);
Item* get_rewrite_result() const { return result; }
Date_cmp_func_rewriter() = delete;
Date_cmp_func_rewriter(const Date_cmp_func_rewriter&) = delete;
Date_cmp_func_rewriter(Date_cmp_func_rewriter&&) = delete;
private:
bool check_cond_match_and_prepare(Item_bool_rowready_func2 *item_func);
Item_field *is_date_rounded_field(Item* item,
const Type_handler *comparison_type,
Item_func::Functype *out_func_type) const;
void rewrite_le_gt_lt_ge();
Item *create_start_bound();
Item *create_end_bound();
Item *create_cmp_func(Item_func::Functype func_type, Item *arg1, Item *arg2);
THD *thd= nullptr;
Item *const_arg_value= nullptr;
Item_func::Functype rewrite_func_type= Item_func::UNKNOWN_FUNC;
Item_func::Functype argument_func_type= Item_func::UNKNOWN_FUNC;
Item_field *field_ref= nullptr;
Item *result= nullptr;
};
void trace_date_item_rewrite(THD *thd,Item *new_item, Item *old_item);
template<typename T>
Item* do_date_conds_transformation(THD *thd, T *item)
{
Date_cmp_func_rewriter rwr(thd, item);
/* If the rewrite failed for some reason, we get the original item */
Item *new_item= rwr.get_rewrite_result();
trace_date_item_rewrite(thd, new_item, item);
return new_item;
}
#endif
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