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/**
* 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.
*/
#include "mongo/platform/basic.h"
#include "mongo/db/index/wildcard_key_generator.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/query/collation/collation_index_key.h"
namespace mongo {
namespace {
// If the user does not specify any projection, then we default to a projection of {_id: 0} in order
// to prevent the _id field from being indexed, since it already has its own dedicated index.
static const BSONObj kDefaultProjection = BSON("_id"_sd << 0);
// If the enclosing object is an array, then the current element's fieldname is the array index, so
// we omit this when computing the full path. Otherwise, the full path is the pathPrefix plus the
// element's fieldname.
void pushPathComponent(BSONElement elem, bool enclosingObjIsArray, FieldRef* pathPrefix) {
if (!enclosingObjIsArray) {
pathPrefix->appendPart(elem.fieldNameStringData());
}
}
// If the enclosing object is not an array, then the final path component should be its field name.
// Verify that this is the case and then pop it off the FieldRef.
void popPathComponent(BSONElement elem, bool enclosingObjIsArray, FieldRef* pathToElem) {
if (!enclosingObjIsArray) {
invariant(pathToElem->getPart(pathToElem->numParts() - 1) == elem.fieldNameStringData());
pathToElem->removeLastPart();
}
}
} // namespace
constexpr StringData WildcardKeyGenerator::kSubtreeSuffix;
std::unique_ptr<ProjectionExecAgg> WildcardKeyGenerator::createProjectionExec(
BSONObj keyPattern, BSONObj pathProjection) {
// We should never have a key pattern that contains more than a single element.
invariant(keyPattern.nFields() == 1);
// The _keyPattern is either { "$**": ±1 } for all paths or { "path.$**": ±1 } for a single
// subtree. If we are indexing a single subtree, then we will project just that path.
auto indexRoot = keyPattern.firstElement().fieldNameStringData();
auto suffixPos = indexRoot.find(kSubtreeSuffix);
// If we're indexing a single subtree, we can't also specify a path projection.
invariant(suffixPos == std::string::npos || pathProjection.isEmpty());
// If this is a subtree projection, the projection spec is { "path.to.subtree": 1 }. Otherwise,
// we use the path projection from the original command object. If the path projection is empty
// we default to {_id: 0}, since empty projections are illegal and will be rejected when parsed.
auto projSpec = (suffixPos != std::string::npos
? BSON(indexRoot.substr(0, suffixPos) << 1)
: pathProjection.isEmpty() ? kDefaultProjection : pathProjection);
// If the projection spec does not explicitly specify _id, we exclude it by default. We also
// prevent the projection from recursing through nested arrays, in order to ensure that the
// output document aligns with the match system's expectations.
return ProjectionExecAgg::create(
projSpec,
ProjectionExecAgg::DefaultIdPolicy::kExcludeId,
ProjectionExecAgg::ArrayRecursionPolicy::kDoNotRecurseNestedArrays);
}
WildcardKeyGenerator::WildcardKeyGenerator(BSONObj keyPattern,
BSONObj pathProjection,
const CollatorInterface* collator)
: _collator(collator), _keyPattern(keyPattern) {
_projExec = createProjectionExec(keyPattern, pathProjection);
}
void WildcardKeyGenerator::generateKeys(BSONObj inputDoc,
BSONObjSet* keys,
BSONObjSet* multikeyPaths) const {
FieldRef rootPath;
_traverseWildcard(_projExec->applyProjection(inputDoc), false, &rootPath, keys, multikeyPaths);
}
void WildcardKeyGenerator::_traverseWildcard(BSONObj obj,
bool objIsArray,
FieldRef* path,
BSONObjSet* keys,
BSONObjSet* multikeyPaths) const {
for (const auto elem : obj) {
// If the element's fieldName contains a ".", fast-path skip it because it's not queryable.
if (elem.fieldNameStringData().find('.', 0) != std::string::npos)
continue;
// Append the element's fieldname to the path, if the enclosing object is not an array.
pushPathComponent(elem, objIsArray, path);
switch (elem.type()) {
case BSONType::Array:
// If this is a nested array, we don't descend it but instead index it as a value.
if (_addKeyForNestedArray(elem, *path, objIsArray, keys))
break;
// Add an entry for the multi-key path, and then fall through to BSONType::Object.
_addMultiKey(*path, multikeyPaths);
case BSONType::Object:
if (_addKeyForEmptyLeaf(elem, *path, keys))
break;
_traverseWildcard(
elem.Obj(), elem.type() == BSONType::Array, path, keys, multikeyPaths);
break;
default:
_addKey(elem, *path, keys);
}
// Remove the element's fieldname from the path, if it was pushed onto it earlier.
popPathComponent(elem, objIsArray, path);
}
}
bool WildcardKeyGenerator::_addKeyForNestedArray(BSONElement elem,
const FieldRef& fullPath,
bool enclosingObjIsArray,
BSONObjSet* keys) const {
// If this element is an array whose parent is also an array, index it as a value.
if (enclosingObjIsArray && elem.type() == BSONType::Array) {
_addKey(elem, fullPath, keys);
return true;
}
return false;
}
bool WildcardKeyGenerator::_addKeyForEmptyLeaf(BSONElement elem,
const FieldRef& fullPath,
BSONObjSet* keys) const {
invariant(elem.isABSONObj());
if (elem.embeddedObject().isEmpty()) {
// In keeping with the behaviour of regular indexes, an empty object is indexed as-is while
// empty arrays are indexed as 'undefined'.
_addKey(elem.type() == BSONType::Array ? BSONElement{} : elem, fullPath, keys);
return true;
}
return false;
}
void WildcardKeyGenerator::_addKey(BSONElement elem,
const FieldRef& fullPath,
BSONObjSet* keys) const {
// Wildcard keys are of the form { "": "path.to.field", "": <collation-aware value> }.
BSONObjBuilder bob;
bob.append("", fullPath.dottedField());
if (elem) {
CollationIndexKey::collationAwareIndexKeyAppend(elem, _collator, &bob);
} else {
bob.appendUndefined("");
}
keys->insert(bob.obj());
}
void WildcardKeyGenerator::_addMultiKey(const FieldRef& fullPath, BSONObjSet* multikeyPaths) const {
// Multikey paths are denoted by a key of the form { "": 1, "": "path.to.array" }. The argument
// 'multikeyPaths' may be nullptr if the access method is being used in an operation which does
// not require multikey path generation.
if (multikeyPaths) {
multikeyPaths->insert(BSON("" << 1 << "" << fullPath.dottedField()));
}
}
} // namespace mongo
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