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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/db/query/parsed_projection.h"
#include "mongo/bson/simple_bsonobj_comparator.h"
#include "mongo/db/query/query_request.h"
namespace mongo {
using std::string;
using std::unique_ptr;
/**
* Parses the projection 'spec' and checks its validity with respect to the query 'query'.
* Puts covering information into 'out'.
*
* Does not take ownership of 'query'.
*
* Returns Status::OK() if it's a valid spec.
* Returns a Status indicating how it's invalid otherwise.
*/
// static
Status ParsedProjection::make(OperationContext* opCtx,
const BSONObj& spec,
const MatchExpression* const query,
ParsedProjection** out) {
// Whether we're including or excluding fields.
enum class IncludeExclude { kUninitialized, kInclude, kExclude };
IncludeExclude includeExclude = IncludeExclude::kUninitialized;
bool requiresDocument = false;
bool hasIndexKeyProjection = false;
bool wantTextScore = false;
bool wantGeoNearPoint = false;
bool wantGeoNearDistance = false;
bool wantSortKey = false;
// Until we see a positional or elemMatch operator we're normal.
ArrayOpType arrayOpType = ARRAY_OP_NORMAL;
// Fill out the returned obj.
unique_ptr<ParsedProjection> pp(new ParsedProjection());
pp->_hasId = true;
for (auto&& elem : spec) {
if (Object == elem.type()) {
BSONObj obj = elem.embeddedObject();
if (1 != obj.nFields()) {
return Status(ErrorCodes::BadValue, ">1 field in obj: " + obj.toString());
}
BSONElement e2 = obj.firstElement();
if (e2.fieldNameStringData() == "$slice") {
if (e2.isNumber()) {
// This is A-OK.
} else if (e2.type() == Array) {
BSONObj arr = e2.embeddedObject();
if (2 != arr.nFields()) {
return Status(ErrorCodes::BadValue, "$slice array wrong size");
}
BSONObjIterator it(arr);
// Skip over 'skip'.
it.next();
int limit = it.next().numberInt();
if (limit <= 0) {
return Status(ErrorCodes::BadValue, "$slice limit must be positive");
}
} else {
return Status(ErrorCodes::BadValue,
"$slice only supports numbers and [skip, limit] arrays");
}
// Projections with $slice aren't covered.
requiresDocument = true;
pp->_arrayFields.push_back(elem.fieldNameStringData());
} else if (e2.fieldNameStringData() == "$elemMatch") {
// Validate $elemMatch arguments and dependencies.
if (Object != e2.type()) {
return Status(ErrorCodes::BadValue,
"elemMatch: Invalid argument, object required.");
}
if (ARRAY_OP_POSITIONAL == arrayOpType) {
return Status(ErrorCodes::BadValue,
"Cannot specify positional operator and $elemMatch.");
}
if (str::contains(elem.fieldName(), '.')) {
return Status(ErrorCodes::BadValue,
"Cannot use $elemMatch projection on a nested field.");
}
arrayOpType = ARRAY_OP_ELEM_MATCH;
// Create a MatchExpression for the elemMatch.
BSONObj elemMatchObj = elem.wrap();
invariant(elemMatchObj.isOwned());
// We pass a null pointer instead of threading through the CollatorInterface. This
// is ok because the parsed MatchExpression is not used after being created. We are
// only parsing here in order to ensure that the elemMatch projection is valid.
//
// Match expression extensions such as $text, $where, $geoNear, $near, and
// $nearSphere are not allowed in $elemMatch projections. $expr and $jsonSchema are
// not allowed because the matcher is not applied to the root of the document.
const CollatorInterface* collator = nullptr;
boost::intrusive_ptr<ExpressionContext> expCtx(
new ExpressionContext(opCtx, collator));
StatusWithMatchExpression statusWithMatcher =
MatchExpressionParser::parse(elemMatchObj,
std::move(expCtx),
ExtensionsCallbackNoop(),
MatchExpressionParser::kBanAllSpecialFeatures);
if (!statusWithMatcher.isOK()) {
return statusWithMatcher.getStatus();
}
// Projections with $elemMatch aren't covered.
requiresDocument = true;
pp->_arrayFields.push_back(elem.fieldNameStringData());
} else if (e2.fieldNameStringData() == "$meta") {
// Field for meta must be top level. We can relax this at some point.
if (str::contains(elem.fieldName(), '.')) {
return Status(ErrorCodes::BadValue, "field for $meta cannot be nested");
}
// Make sure the argument to $meta is something we recognize.
// e.g. {x: {$meta: "textScore"}}
if (String != e2.type()) {
return Status(ErrorCodes::BadValue, "unexpected argument to $meta in proj");
}
if (e2.valuestr() != QueryRequest::metaTextScore &&
e2.valuestr() != QueryRequest::metaRecordId &&
e2.valuestr() != QueryRequest::metaIndexKey &&
e2.valuestr() != QueryRequest::metaGeoNearDistance &&
e2.valuestr() != QueryRequest::metaGeoNearPoint &&
e2.valuestr() != QueryRequest::metaSortKey) {
return Status(ErrorCodes::BadValue, "unsupported $meta operator: " + e2.str());
}
// This clobbers everything else.
if (e2.valuestr() == QueryRequest::metaTextScore) {
wantTextScore = true;
} else if (e2.valuestr() == QueryRequest::metaIndexKey) {
hasIndexKeyProjection = true;
} else if (e2.valuestr() == QueryRequest::metaGeoNearDistance) {
wantGeoNearDistance = true;
} else if (e2.valuestr() == QueryRequest::metaGeoNearPoint) {
wantGeoNearPoint = true;
} else if (e2.valuestr() == QueryRequest::metaSortKey) {
wantSortKey = true;
}
// Of the $meta projections, only sortKey can be covered.
if (e2.valuestr() != QueryRequest::metaSortKey) {
requiresDocument = true;
}
pp->_metaFields.push_back(elem.fieldNameStringData());
} else {
return Status(ErrorCodes::BadValue,
string("Unsupported projection option: ") + elem.toString());
}
} else if ((elem.fieldNameStringData() == "_id") && !elem.trueValue()) {
pp->_hasId = false;
} else {
pp->_hasDottedFieldPath = pp->_hasDottedFieldPath ||
elem.fieldNameStringData().find('.') != std::string::npos;
if (elem.trueValue()) {
pp->_includedFields.push_back(elem.fieldNameStringData());
} else {
pp->_excludedFields.push_back(elem.fieldNameStringData());
}
// If we haven't specified an include/exclude, initialize includeExclude. We expect
// further include/excludes to match it.
if (includeExclude == IncludeExclude::kUninitialized) {
includeExclude =
elem.trueValue() ? IncludeExclude::kInclude : IncludeExclude::kExclude;
} else if ((includeExclude == IncludeExclude::kInclude && !elem.trueValue()) ||
(includeExclude == IncludeExclude::kExclude && elem.trueValue())) {
return Status(ErrorCodes::BadValue,
"Projection cannot have a mix of inclusion and exclusion.");
}
}
if (_isPositionalOperator(elem.fieldName())) {
// Validate the positional op.
if (!elem.trueValue()) {
return Status(ErrorCodes::BadValue,
"Cannot exclude array elements with the positional operator.");
}
if (ARRAY_OP_POSITIONAL == arrayOpType) {
return Status(ErrorCodes::BadValue,
"Cannot specify more than one positional proj. per query.");
}
if (ARRAY_OP_ELEM_MATCH == arrayOpType) {
return Status(ErrorCodes::BadValue,
"Cannot specify positional operator and $elemMatch.");
}
StringData after = str::after(elem.fieldNameStringData(), ".$");
if (after.find(".$"_sd) != std::string::npos) {
str::stream ss;
ss << "Positional projection '" << elem.fieldName() << "' contains "
<< "the positional operator more than once.";
return Status(ErrorCodes::BadValue, ss);
}
StringData matchfield = str::before(elem.fieldNameStringData(), '.');
if (query && !_hasPositionalOperatorMatch(query, matchfield)) {
str::stream ss;
ss << "Positional projection '" << elem.fieldName() << "' does not "
<< "match the query document.";
return Status(ErrorCodes::BadValue, ss);
}
arrayOpType = ARRAY_OP_POSITIONAL;
pp->_arrayFields.push_back(elem.fieldNameStringData());
}
}
// If includeExclude is uninitialized or set to exclude fields, then we can't use an index
// because we don't know what fields we're missing.
if (includeExclude == IncludeExclude::kUninitialized ||
includeExclude == IncludeExclude::kExclude) {
requiresDocument = true;
}
pp->_isInclusionProjection = (includeExclude == IncludeExclude::kInclude);
// The positional operator uses the MatchDetails from the query
// expression to know which array element was matched.
pp->_requiresMatchDetails = arrayOpType == ARRAY_OP_POSITIONAL;
// Save the raw spec. It should be owned by the QueryRequest.
verify(spec.isOwned());
pp->_source = spec;
pp->_returnKey = hasIndexKeyProjection;
pp->_requiresDocument = requiresDocument;
// Add meta-projections.
pp->_wantTextScore = wantTextScore;
pp->_wantGeoNearPoint = wantGeoNearPoint;
pp->_wantGeoNearDistance = wantGeoNearDistance;
pp->_wantSortKey = wantSortKey;
// If it's possible to compute the projection in a covered fashion, populate _requiredFields
// so the planner can perform projection analysis.
if (!pp->_requiresDocument) {
if (pp->_hasId) {
pp->_requiredFields.push_back("_id");
}
// The only way we could be here is if spec is only simple non-dotted-field inclusions or
// the $meta sortKey projection. Therefore we can iterate over spec to get the fields
// required.
BSONObjIterator srcIt(spec);
while (srcIt.more()) {
BSONElement elt = srcIt.next();
// We've already handled the _id field before entering this loop.
if (pp->_hasId && (elt.fieldNameStringData() == "_id")) {
continue;
}
// $meta sortKey should not be checked as a part of _requiredFields, since it can
// potentially produce a covered projection as long as the sort key is covered.
if (BSONType::Object == elt.type()) {
dassert(SimpleBSONObjComparator::kInstance.evaluate(elt.Obj() ==
BSON("$meta"
<< "sortKey")));
continue;
}
if (elt.trueValue()) {
pp->_requiredFields.push_back(elt.fieldName());
}
}
}
// returnKey clobbers everything except for sortKey meta-projection.
if (hasIndexKeyProjection && !wantSortKey) {
pp->_requiresDocument = false;
}
*out = pp.release();
return Status::OK();
}
namespace {
bool isPrefixOf(StringData first, StringData second) {
if (first.size() >= second.size()) {
return false;
}
return second.startsWith(first) && second[first.size()] == '.';
}
} // namespace
bool ParsedProjection::isFieldRetainedExactly(StringData path) const {
// If a path, or a parent or child of the path, is contained in _metaFields or in _arrayFields,
// our output likely does not preserve that field.
for (auto&& metaField : _metaFields) {
if (path == metaField || isPrefixOf(path, metaField) || isPrefixOf(metaField, path)) {
return false;
}
}
for (auto&& arrayField : _arrayFields) {
if (path == arrayField || isPrefixOf(path, arrayField) || isPrefixOf(arrayField, path)) {
return false;
}
}
if (path == "_id" || isPrefixOf("_id", path)) {
return _hasId;
}
if (!_isInclusionProjection) {
// If we are an exclusion projection, and the path, or a parent or child of the path, is
// contained in _excludedFields, our output likely does not preserve that field.
for (auto&& excluded : _excludedFields) {
if (path == excluded || isPrefixOf(excluded, path) || isPrefixOf(path, excluded)) {
return false;
}
}
} else {
// If we are an inclusion projection, we may include parents of this path, but we cannot
// include children.
bool fieldIsIncluded = false;
// In a projection with several statements, the last one takes precedence. For example, the
// projection {a: 1, a.b: 1} preserves 'a.b', but not 'a'.
// TODO SERVER-6527: Simplify this when projections are no longer order-dependent.
for (auto&& included : _includedFields) {
if (path == included || isPrefixOf(included, path)) {
fieldIsIncluded = true;
} else if (isPrefixOf(path, included)) {
fieldIsIncluded = false;
}
}
if (!fieldIsIncluded) {
return false;
}
}
return true;
}
// static
bool ParsedProjection::_isPositionalOperator(const char* fieldName) {
return str::contains(fieldName, ".$") && !str::contains(fieldName, ".$ref") &&
!str::contains(fieldName, ".$id") && !str::contains(fieldName, ".$db");
}
// static
bool ParsedProjection::_hasPositionalOperatorMatch(const MatchExpression* const query,
StringData matchfield) {
if (query->getCategory() == MatchExpression::MatchCategory::kLogical) {
for (unsigned int i = 0; i < query->numChildren(); ++i) {
if (_hasPositionalOperatorMatch(query->getChild(i), matchfield)) {
return true;
}
}
} else {
StringData queryPath = query->path();
// We have to make a distinction between match expressions that are
// initialized with an empty field/path name "" and match expressions
// for which the path is not meaningful (eg. $where).
if (!queryPath.rawData()) {
return false;
}
StringData pathPrefix = str::before(queryPath, '.');
return pathPrefix == matchfield;
}
return false;
}
} // namespace mongo
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