1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
|
/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* 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
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kQuery
#include "mongo/platform/basic.h"
#include "mongo/db/matcher/rewrite_expr.h"
#include "mongo/db/matcher/expression_internal_expr_eq.h"
#include "mongo/db/matcher/expression_leaf.h"
#include "mongo/db/matcher/expression_tree.h"
#include "mongo/util/log.h"
namespace mongo {
using CmpOp = ExpressionCompare::CmpOp;
RewriteExpr::RewriteResult RewriteExpr::rewrite(const boost::intrusive_ptr<Expression>& expression,
const CollatorInterface* collator) {
LOG(5) << "Expression prior to rewrite: " << expression->serialize(false);
RewriteExpr rewriteExpr(collator);
std::unique_ptr<MatchExpression> matchExpression;
if (auto matchTree = rewriteExpr._rewriteExpression(expression)) {
matchExpression = std::move(matchTree);
LOG(5) << "Post-rewrite MatchExpression: " << matchExpression->debugString();
matchExpression = MatchExpression::optimize(std::move(matchExpression));
LOG(5) << "Post-rewrite/post-optimized MatchExpression: " << matchExpression->debugString();
}
return {std::move(matchExpression), std::move(rewriteExpr._matchExprElemStorage)};
}
std::unique_ptr<MatchExpression> RewriteExpr::_rewriteExpression(
const boost::intrusive_ptr<Expression>& currExprNode) {
if (auto expr = dynamic_cast<ExpressionAnd*>(currExprNode.get())) {
return _rewriteAndExpression(expr);
} else if (auto expr = dynamic_cast<ExpressionOr*>(currExprNode.get())) {
return _rewriteOrExpression(expr);
} else if (auto expr = dynamic_cast<ExpressionCompare*>(currExprNode.get())) {
return _rewriteComparisonExpression(expr);
}
return nullptr;
}
std::unique_ptr<MatchExpression> RewriteExpr::_rewriteAndExpression(
const boost::intrusive_ptr<ExpressionAnd>& currExprNode) {
auto andMatch = std::make_unique<AndMatchExpression>();
for (auto&& child : currExprNode->getOperandList()) {
if (auto childMatch = _rewriteExpression(child)) {
andMatch->add(childMatch.release());
}
}
if (andMatch->numChildren() > 0) {
return std::move(andMatch);
}
return nullptr;
}
std::unique_ptr<MatchExpression> RewriteExpr::_rewriteOrExpression(
const boost::intrusive_ptr<ExpressionOr>& currExprNode) {
auto orMatch = std::make_unique<OrMatchExpression>();
for (auto&& child : currExprNode->getOperandList()) {
if (auto childExpr = _rewriteExpression(child)) {
orMatch->add(childExpr.release());
} else {
// If any child cannot be rewritten to a MatchExpression then we must abandon adding
// this $or clause.
return nullptr;
}
}
if (orMatch->numChildren() > 0) {
return std::move(orMatch);
}
return nullptr;
}
std::unique_ptr<MatchExpression> RewriteExpr::_rewriteComparisonExpression(
const boost::intrusive_ptr<ExpressionCompare>& expr) {
if (!_canRewriteComparison(expr)) {
return nullptr;
}
const auto& operandList = expr->getOperandList();
invariant(operandList.size() == 2);
ExpressionFieldPath* lhs{nullptr};
ExpressionConstant* rhs{nullptr};
CmpOp cmpOperator = expr->getOp();
// Extract left-hand side and right-hand side MatchExpression components.
if ((lhs = dynamic_cast<ExpressionFieldPath*>(operandList[0].get()))) {
rhs = dynamic_cast<ExpressionConstant*>(operandList[1].get());
invariant(rhs);
} else {
lhs = dynamic_cast<ExpressionFieldPath*>(operandList[1].get());
rhs = dynamic_cast<ExpressionConstant*>(operandList[0].get());
invariant(lhs && rhs);
}
// Build argument for ComparisonMatchExpression.
const auto fieldPath = lhs->getFieldPath().tail();
BSONObjBuilder bob;
bob << fieldPath.fullPath() << rhs->getValue();
auto cmpObj = bob.obj();
_matchExprElemStorage.push_back(cmpObj);
return _buildComparisonMatchExpression(cmpOperator, cmpObj.firstElement());
}
std::unique_ptr<MatchExpression> RewriteExpr::_buildComparisonMatchExpression(
ExpressionCompare::CmpOp comparisonOp, BSONElement fieldAndValue) {
invariant(comparisonOp == ExpressionCompare::EQ);
auto eqMatchExpr =
std::make_unique<InternalExprEqMatchExpression>(fieldAndValue.fieldName(), fieldAndValue);
eqMatchExpr->setCollator(_collator);
return std::move(eqMatchExpr);
}
bool RewriteExpr::_canRewriteComparison(
const boost::intrusive_ptr<ExpressionCompare>& expression) const {
// Currently we only rewrite $eq expressions.
if (expression->getOp() != ExpressionCompare::EQ) {
return false;
}
const auto& operandList = expression->getOperandList();
bool hasFieldPath = false;
for (auto operand : operandList) {
if (auto exprFieldPath = dynamic_cast<ExpressionFieldPath*>(operand.get())) {
if (!exprFieldPath->isRootFieldPath()) {
// This field path refers to a variable rather than a local document field path.
return false;
}
if (hasFieldPath) {
// Match does not allow for more than one local document field path.
return false;
}
hasFieldPath = true;
} else if (auto exprConst = dynamic_cast<ExpressionConstant*>(operand.get())) {
switch (exprConst->getValue().getType()) {
case BSONType::Array:
case BSONType::EOO:
case BSONType::Undefined:
return false;
default:
break;
}
} else {
return false;
}
}
return hasFieldPath;
}
} // namespace mongo
|
