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74 lines
3.3 KiB
74 lines
3.3 KiB
5 months ago
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#ifndef SQL_CONST_FOLDING_INCLUDED
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#define SQL_CONST_FOLDING_INCLUDED
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/* Copyright (c) 2018, 2019, Oracle and/or its affiliates. All rights reserved.
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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, version 2.0,
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as published by the Free Software Foundation.
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This program is also distributed with certain software (including
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but not limited to OpenSSL) that is licensed under separate terms,
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as designated in a particular file or component or in included license
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documentation. The authors of MySQL hereby grant you an additional
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permission to link the program and your derivative works with the
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separately licensed software that they have included with MySQL.
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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, version 2.0, 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 St, Fifth Floor, Boston, MA 02110-1301 USA */
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/**
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@file sql/sql_const_folding.h
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Interface to SQL expression constant folding
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*/
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#include "sql/item.h" // Item, Item::cond_result
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class THD;
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/**
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Fold boolean condition {=, <>, >, >=, <, <=, <=>} involving constants and
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fields (or references to fields), possibly determining if the condition is
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always true or false based on type range of the field, or possibly simplifying
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>=, <= to = if constant lies on the range border.
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Also fold such conditions if they are present as arguments of other functions
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in the same way, except there we replace the arguments with manifest FALSE or
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field <> field to exclude NULLs if the field is nullable, cf.
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ignore_unknown().
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The constants are always converted to constants of the type of the field, no
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widening of the field type in therefore necessary after this folding for
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comparison to occur. When converting constants to decimal (when the field is a
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decimal), the constant will receive the same number of fractional decimals as
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the field. If decimal constant fraction truncation occurs, the comparison
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{GT,GE,LT,LE} logic is adjusted to preserve semantics without widening the
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field's type.
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@param thd session state
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@param cond the condition to handle
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@param[out] retcond condition after const removal
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@param[out] cond_value resulting value of the condition
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- COND_OK: condition must be evaluated (e.g int == 3)
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- COND_TRUE: always true (e.g signed tinyint < 128)
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- COND_FALSE: always false (e.g unsigned tinyint < 0)
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@param manifest_result
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For IS NOT NULL on a not nullable item, if true,
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return item TRUE (1), else remove condition and return
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COND_TRUE. For cmp items, this is determined by
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Item_bool_func2::ignore_unknown.
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@returns false if success, true if error
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*/
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bool fold_condition(THD *thd, Item *cond, Item **retcond,
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Item::cond_result *cond_value,
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bool manifest_result = false);
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#endif /* SQL_CONST_FOLDING_INCLUDED */
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