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f0b665f880
Rewrite datetime comparison conditions into sargeable. For example,
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 BETWEEN YEAR_START(val) AND YEAR_END(val)
Do the same with DATE(col), for example:
DATE(col) <= val -> col <= DAY_END(val)
After such a rewrite index lookup on column "col" can be employed
111 lines
3.6 KiB
C++
111 lines
3.6 KiB
C++
/*
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Copyright (c) 2023, MariaDB
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA */
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#ifndef OPT_REWRITE_DATE_CMP_INCLUDED
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#define OPT_REWRITE_DATE_CMP_INCLUDED
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class Item_func_eq;
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class Item_func_ge;
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class Item_func_gt;
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class Item_func_le;
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class Item_func_lt;
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class Item_bool_rowready_func2;
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/*
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@brief Class responsible for rewriting datetime comparison condition.
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It rewrites non-sargable conditions into sargable.
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@detail
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The intent of this class is to do equivalent rewrites as follows:
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YEAR(col) <= val -> col <= year_end(val)
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YEAR(col) < val -> col < year_start(val)
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YEAR(col) >= val -> col >= year_start(val)
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YEAR(col) > val -> col > year_end(val)
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YEAR(col) = val -> col >= year_start(val) AND col<=year_end(val)
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Also the same is done for comparisons with DATE(col):
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DATE(col) <= val -> col <= day_end(val)
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if col has a DATE type (not DATETIME), then the rewrite becomes:
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DATE(col) <= val -> col <= val
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@usage
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Date_cmp_func_rewriter rwr(thd, item_func);
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Item *new_item= rwr.get_rewrite_result();
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Returned new_item points to an item that item_func was rewritten to.
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new_item already has fixed fields (fix_fields() was called).
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If no rewrite happened, new_item points to the initial item_func parameter
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@todo
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Also handle conditions in form "YEAR(date_col) BETWEEN 2014 AND 2017"
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and "YEAR(col) = c1 AND MONTH(col) = c2"
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*/
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class Date_cmp_func_rewriter
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{
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public:
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Date_cmp_func_rewriter(THD* thd, Item_func_eq *item_func);
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Date_cmp_func_rewriter(THD* thd, Item_func_ge *item_func);
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Date_cmp_func_rewriter(THD* thd, Item_func_gt *item_func);
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Date_cmp_func_rewriter(THD* thd, Item_func_le *item_func);
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Date_cmp_func_rewriter(THD* thd, Item_func_lt *item_func);
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Item* get_rewrite_result() const { return result; }
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Date_cmp_func_rewriter() = delete;
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Date_cmp_func_rewriter(const Date_cmp_func_rewriter&) = delete;
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Date_cmp_func_rewriter(Date_cmp_func_rewriter&&) = delete;
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private:
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bool check_cond_match_and_prepare(Item_bool_rowready_func2 *item_func);
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Item_field *is_date_rounded_field(Item* item,
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const Type_handler *comparison_type,
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Item_func::Functype *out_func_type) const;
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void rewrite_le_gt_lt_ge();
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Item *create_start_bound();
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Item *create_end_bound();
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Item *create_cmp_func(Item_func::Functype func_type, Item *arg1, Item *arg2);
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THD *thd= nullptr;
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Item *const_arg_value= nullptr;
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Item_func::Functype rewrite_func_type= Item_func::UNKNOWN_FUNC;
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Item_func::Functype argument_func_type= Item_func::UNKNOWN_FUNC;
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Item_field *field_ref= nullptr;
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Item *result= nullptr;
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};
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void trace_date_item_rewrite(THD *thd,Item *new_item, Item *old_item);
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template<typename T>
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Item* do_date_conds_transformation(THD *thd, T *item)
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{
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Date_cmp_func_rewriter rwr(thd, item);
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/* If the rewrite failed for some reason, we get the original item */
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Item *new_item= rwr.get_rewrite_result();
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trace_date_item_rewrite(thd, new_item, item);
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return new_item;
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}
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#endif
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