MySQL
9.0.0
Source Code Documentation
common_subexpression_elimination.h
Go to the documentation of this file.
1
/* Copyright (c) 2021, 2024, Oracle and/or its affiliates.
2
3
This program is free software; you can redistribute it and/or modify
4
it under the terms of the GNU General Public License, version 2.0,
5
as published by the Free Software Foundation.
6
7
This program is designed to work with certain software (including
8
but not limited to OpenSSL) that is licensed under separate terms,
9
as designated in a particular file or component or in included license
10
documentation. The authors of MySQL hereby grant you an additional
11
permission to link the program and your derivative works with the
12
separately licensed software that they have either included with
13
the program or referenced in the documentation.
14
15
This program is distributed in the hope that it will be useful,
16
but WITHOUT ANY WARRANTY; without even the implied warranty of
17
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18
GNU General Public License, version 2.0, for more details.
19
20
You should have received a copy of the GNU General Public License
21
along with this program; if not, write to the Free Software
22
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
23
24
#ifndef SQL_JOIN_OPTIMIZER_COMMON_SUBEXPRESSION_ELIMINATION
25
#define SQL_JOIN_OPTIMIZER_COMMON_SUBEXPRESSION_ELIMINATION 1
26
27
class
Item
;
28
29
/**
30
Do simple CSE (common subexpression elimination) on “item”, and return
31
the answer. The CSE done is exclusively moving common expressions out
32
of conjunctions-of-disjunctions, ie. it rewrites
33
34
(a AND b) OR (a AND c)
35
36
into
37
38
a AND (b OR c)
39
40
The primary motivation is that such split-out items are more versatile;
41
they can be pushed independently, be made into hash join conditions etc.
42
However, an added bonus is that the expressions will simply execute faster.
43
44
This function does not descend into subexpressions that are not AND/OR
45
conjunctions, so e.g. an expression like
46
47
1 + ((a AND b) OR (a AND c))
48
49
will be left as-is.
50
*/
51
Item
*
CommonSubexpressionElimination
(
Item
*cond);
52
53
#endif
// SQL_JOIN_OPTIMIZER_COMMON_SUBEXPRESSION_ELIMINATION
Item
Base class that is used to represent any kind of expression in a relational query.
Definition:
item.h:930
CommonSubexpressionElimination
Item * CommonSubexpressionElimination(Item *cond)
Do simple CSE (common subexpression elimination) on “item”, and return the answer.
Definition:
common_subexpression_elimination.cc:178
sql
join_optimizer
common_subexpression_elimination.h
Generated by
1.9.2