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* Copyright (C) 2011 10gen Inc.
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* GNU Affero General Public License for more details.
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <>.
* 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 GNU Affero General 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/pipeline/document_source_match.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/matcher/expression_algo.h"
#include "mongo/db/matcher/expression_array.h"
#include "mongo/db/matcher/expression_leaf.h"
#include "mongo/db/matcher/extensions_callback_noop.h"
#include "mongo/db/pipeline/document.h"
#include "mongo/db/pipeline/expression.h"
#include "mongo/db/pipeline/lite_parsed_document_source.h"
#include "mongo/stdx/memory.h"
#include "mongo/util/stringutils.h"
namespace mongo {
using boost::intrusive_ptr;
using std::pair;
using std::unique_ptr;
using std::string;
using std::vector;
const char* DocumentSourceMatch::getSourceName() const {
return "$match";
Value DocumentSourceMatch::serialize(boost::optional<ExplainOptions::Verbosity> explain) const {
return Value(DOC(getSourceName() << Document(getQuery())));
intrusive_ptr<DocumentSource> DocumentSourceMatch::optimize() {
return getQuery().isEmpty() ? nullptr : this;
DocumentSource::GetNextResult DocumentSourceMatch::getNext() {
// The user facing error should have been generated earlier.
massert(17309, "Should never call getNext on a $match stage with $text clause", !_isTextQuery);
auto nextInput = pSource->getNext();
for (; nextInput.isAdvanced(); nextInput = pSource->getNext()) {
// MatchExpression only takes BSON documents, so we have to make one. As an optimization,
// only serialize the fields we need to do the match.
BSONObj toMatch = _dependencies.needWholeDocument
? nextInput.getDocument().toBson()
: getObjectForMatch(nextInput.getDocument(), _dependencies.fields);
if (_expression->matchesBSON(toMatch)) {
return nextInput;
// For performance reasons, a streaming stage must not keep references to documents across
// calls to getNext(). Such stages must retrieve a result from their child and then release
// it (or return it) before asking for another result. Failing to do so can result in extra
// work, since the Document/Value library must copy data on write when that data has a
// refcount above one.
return nextInput;
Pipeline::SourceContainer::iterator DocumentSourceMatch::doOptimizeAt(
Pipeline::SourceContainer::iterator itr, Pipeline::SourceContainer* container) {
invariant(*itr == this);
auto nextMatch = dynamic_cast<DocumentSourceMatch*>((*std::next(itr)).get());
// Since a text search must use an index, it must be the first stage in the pipeline. We cannot
// combine a non-text stage with a text stage, as that may turn an invalid pipeline into a
// valid one, unbeknownst to the user.
if (nextMatch) {
// Text queries are not allowed anywhere except as the first stage. This is checked before
// optimization.
// Merge 'nextMatch' into this stage.
// Erase 'nextMatch'.
return itr == container->begin() ? itr : std::prev(itr);
return std::next(itr);
BSONObj DocumentSourceMatch::getObjectForMatch(const Document& input,
const std::set<std::string>& fields) {
BSONObjBuilder matchObject;
for (auto&& field : fields) {
// getNestedField does not handle dotted paths correctly, so instead of retrieving the
// entire path, we just extract the first element of the path.
const auto prefix = FieldPath::extractFirstFieldFromDottedPath(field);
if (!matchObject.hasField(prefix)) {
// Avoid adding the same prefix twice.
input.getField(prefix).addToBsonObj(&matchObject, prefix);
return matchObject.obj();
namespace {
// This block contains the functions that make up the implementation of
// DocumentSourceMatch::redactSafePortion(). They will only be called after
// the Match expression has been successfully parsed so they can assume that
// input is well formed.
bool isAllDigits(StringData str) {
if (str.empty())
return false;
for (size_t i = 0; i < str.size(); i++) {
if (!isdigit(str[i]))
return false;
return true;
bool isFieldnameRedactSafe(StringData fieldName) {
// Can't have numeric elements in the dotted path since redacting elements from an array
// would change the indexes.
const size_t dotPos = fieldName.find('.');
if (dotPos == string::npos)
return !isAllDigits(fieldName);
const StringData part = fieldName.substr(0, dotPos);
const StringData rest = fieldName.substr(dotPos + 1);
return !isAllDigits(part) && isFieldnameRedactSafe(rest);
bool isTypeRedactSafeInComparison(BSONType type) {
if (type == Array)
return false;
if (type == Object)
return false;
if (type == jstNULL)
return false;
if (type == Undefined)
return false; // Currently a parse error.
return true;
Document redactSafePortionTopLevel(BSONObj query); // mutually recursive with next function
// Returns the redact-safe portion of an "inner" match expression. This is the layer like
// {$gt: 5} which does not include the field name. Returns an empty document if none of the
// expression can safely be promoted in front of a $redact.
Document redactSafePortionDollarOps(BSONObj expr) {
MutableDocument output;
BSONForEach(field, expr) {
if (field.fieldName()[0] != '$')
if (field.fieldNameStringData() == "$eq") {
if (isTypeRedactSafeInComparison(field.type())) {
output[field.fieldNameStringData()] = Value(field);
switch (BSONObj::MatchType(field.getGtLtOp(BSONObj::Equality))) {
// These are always ok
case BSONObj::opTYPE:
case BSONObj::opREGEX:
case BSONObj::opOPTIONS:
case BSONObj::opMOD:
output[field.fieldNameStringData()] = Value(field);
// These are ok if the type of the rhs is allowed in comparisons
case BSONObj::LTE:
case BSONObj::GTE:
case BSONObj::LT:
case BSONObj::GT:
if (isTypeRedactSafeInComparison(field.type()))
output[field.fieldNameStringData()] = Value(field);
// $in must be all-or-nothing (like $or). Can't include subset of elements.
case BSONObj::opIN: {
bool allOk = true;
BSONForEach(elem, field.Obj()) {
if (!isTypeRedactSafeInComparison(elem.type())) {
allOk = false;
if (allOk) {
output[field.fieldNameStringData()] = Value(field);
case BSONObj::opALL: {
// $all can include subset of elements (like $and).
vector<Value> matches;
BSONForEach(elem, field.Obj()) {
// NOTE this currently doesn't allow {$all: [{$elemMatch: {...}}]}
if (isTypeRedactSafeInComparison(elem.type())) {
if (!matches.empty())
output[field.fieldNameStringData()] = Value(std::move(matches));
case BSONObj::opELEM_MATCH: {
BSONObj subIn = field.Obj();
Document subOut;
if (subIn.firstElementFieldName()[0] == '$') {
subOut = redactSafePortionDollarOps(subIn);
} else {
subOut = redactSafePortionTopLevel(subIn);
if (!subOut.empty())
output[field.fieldNameStringData()] = Value(subOut);
// These are never allowed
case BSONObj::Equality: // This actually means unknown
case BSONObj::opNEAR:
case BSONObj::NE:
case BSONObj::opSIZE:
case BSONObj::NIN:
case BSONObj::opEXISTS:
case BSONObj::opWITHIN:
return output.freeze();
// Returns the redact-safe portion of an "outer" match expression. This is the layer like
// {fieldName: {...}} which does include the field name. Returns an empty document if none of
// the expression can safely be promoted in front of a $redact.
Document redactSafePortionTopLevel(BSONObj query) {
MutableDocument output;
BSONForEach(field, query) {
if (field.fieldName()[0] == '$') {
if (str::equals(field.fieldName(), "$or")) {
// $or must be all-or-nothing (line $in). Can't include subset of elements.
vector<Value> okClauses;
BSONForEach(elem, field.Obj()) {
Document clause = redactSafePortionTopLevel(elem.Obj());
if (clause.empty()) {
if (!okClauses.empty())
output["$or"] = Value(std::move(okClauses));
} else if (str::equals(field.fieldName(), "$and")) {
// $and can include subset of elements (like $all).
vector<Value> okClauses;
BSONForEach(elem, field.Obj()) {
Document clause = redactSafePortionTopLevel(elem.Obj());
if (!clause.empty())
if (!okClauses.empty())
output["$and"] = Value(std::move(okClauses));
if (!isFieldnameRedactSafe(field.fieldNameStringData()))
switch (field.type()) {
case Array:
continue; // exact matches on arrays are never allowed
case jstNULL:
continue; // can't look for missing fields
case Undefined:
continue; // Currently a parse error.
case Object: {
Document sub = redactSafePortionDollarOps(field.Obj());
if (!sub.empty())
output[field.fieldNameStringData()] = Value(sub);
// All other types are ok to pass through
output[field.fieldNameStringData()] = Value(field);
return output.freeze();
BSONObj DocumentSourceMatch::redactSafePortion() const {
return redactSafePortionTopLevel(getQuery()).toBson();
bool DocumentSourceMatch::isTextQuery(const BSONObj& query) {
BSONForEach(e, query) {
const StringData fieldName = e.fieldNameStringData();
if (fieldName == "$text"_sd)
return true;
if (e.isABSONObj() && isTextQuery(e.Obj()))
return true;
return false;
void DocumentSourceMatch::joinMatchWith(intrusive_ptr<DocumentSourceMatch> other) {
_predicate = BSON("$and" << BSON_ARRAY(_predicate << other->getQuery()));
StatusWithMatchExpression status = uassertStatusOK(
MatchExpressionParser::parse(_predicate, ExtensionsCallbackNoop(), pExpCtx->getCollator()));
_expression = std::move(status.getValue());
_dependencies = DepsTracker(_dependencies.getMetadataAvailable());
pair<intrusive_ptr<DocumentSourceMatch>, intrusive_ptr<DocumentSourceMatch>>
DocumentSourceMatch::splitSourceBy(const std::set<std::string>& fields,
const StringMap<std::string>& renames) {
pair<unique_ptr<MatchExpression>, unique_ptr<MatchExpression>> newExpr(
expression::splitMatchExpressionBy(std::move(_expression), fields, renames));
invariant(newExpr.first || newExpr.second);
if (!newExpr.first) {
// The entire $match depends on 'fields'. It cannot be split or moved, so we return this
// stage without modification as the second stage in the pair.
_expression = std::move(newExpr.second);
return {nullptr, this};
if (!newExpr.second && renames.empty()) {
// This $match is entirely independent of 'fields' and there were no renames to apply. In
// this case, the current stage can swap with its predecessor without modification. We
// simply return this as the first stage in the pair.
_expression = std::move(newExpr.first);
return {this, nullptr};
// If we're here, then either:
// - this stage has split into two, or
// - this stage can swap with its predecessor, but potentially had renames applied.
// In any of these cases, we have created new expression(s). A MatchExpression requires that it
// is outlived by the BSONObj it is parsed from. But since the MatchExpressions were modified,
// the corresponding BSONObj may not exist. Therefore, we take each of these expressions,
// serialize them, and then re-parse them, constructing new BSON that is owned by the
// DocumentSourceMatch.
BSONObjBuilder firstBob;
auto firstMatch = DocumentSourceMatch::create(firstBob.obj(), pExpCtx);
intrusive_ptr<DocumentSourceMatch> secondMatch;
if (newExpr.second) {
BSONObjBuilder secondBob;
secondMatch = DocumentSourceMatch::create(secondBob.obj(), pExpCtx);
return {std::move(firstMatch), std::move(secondMatch)};
boost::intrusive_ptr<DocumentSourceMatch> DocumentSourceMatch::descendMatchOnPath(
MatchExpression* matchExpr,
const std::string& descendOn,
const intrusive_ptr<ExpressionContext>& expCtx) {
expression::mapOver(matchExpr, [&descendOn](MatchExpression* node, std::string path) -> void {
// Cannot call this method on a $match including a $elemMatch.
invariant(node->matchType() != MatchExpression::ELEM_MATCH_OBJECT &&
node->matchType() != MatchExpression::ELEM_MATCH_VALUE);
// Logical nodes do not have a path, but both 'leaf' and 'array' nodes
// do.
if (node->isLogical()) {
auto leafPath = node->path();
invariant(expression::isPathPrefixOf(descendOn, leafPath));
auto newPath = leafPath.substr(descendOn.size() + 1);
if (node->isLeaf() && node->matchType() != MatchExpression::TYPE_OPERATOR &&
node->matchType() != MatchExpression::WHERE) {
auto leafNode = static_cast<LeafMatchExpression*>(node);
} else if (node->isArray()) {
auto arrayNode = static_cast<ArrayMatchingMatchExpression*>(node);
BSONObjBuilder query;
return new DocumentSourceMatch(query.obj(), expCtx);
static void uassertNoDisallowedClauses(BSONObj query) {
BSONForEach(e, query) {
// can't use the MatchExpression API because this would segfault the constructor
"$where is not allowed inside of a $match aggregation expression",
!str::equals(e.fieldName(), "$where"));
// geo breaks if it is not the first portion of the pipeline
"$near is not allowed inside of a $match aggregation expression",
!str::equals(e.fieldName(), "$near"));
"$nearSphere is not allowed inside of a $match aggregation expression",
!str::equals(e.fieldName(), "$nearSphere"));
if (e.isABSONObj())
intrusive_ptr<DocumentSourceMatch> DocumentSourceMatch::create(
BSONObj filter, const intrusive_ptr<ExpressionContext>& expCtx) {
intrusive_ptr<DocumentSourceMatch> match(new DocumentSourceMatch(filter, expCtx));
return match;
intrusive_ptr<DocumentSource> DocumentSourceMatch::createFromBson(
BSONElement elem, const intrusive_ptr<ExpressionContext>& pExpCtx) {
uassert(15959, "the match filter must be an expression in an object", elem.type() == Object);
return DocumentSourceMatch::create(elem.Obj(), pExpCtx);
BSONObj DocumentSourceMatch::getQuery() const {
return _predicate;
DocumentSource::GetDepsReturn DocumentSourceMatch::getDependencies(DepsTracker* deps) const {
if (isTextQuery()) {
// A $text aggregation field should return EXHAUSTIVE_ALL, since we don't necessarily know
// what field it will be searching without examining indices.
deps->needWholeDocument = true;
return SEE_NEXT;
void DocumentSourceMatch::addDependencies(DepsTracker* deps) const {
expression::mapOver(_expression.get(), [deps](MatchExpression* node, std::string path) -> void {
if (!path.empty() &&
(node->numChildren() == 0 || node->matchType() == MatchExpression::ELEM_MATCH_VALUE ||
node->matchType() == MatchExpression::ELEM_MATCH_OBJECT)) {
DocumentSourceMatch::DocumentSourceMatch(const BSONObj& query,
const intrusive_ptr<ExpressionContext>& pExpCtx)
: DocumentSource(pExpCtx), _predicate(query.getOwned()), _isTextQuery(isTextQuery(query)) {
StatusWithMatchExpression status = uassertStatusOK(
MatchExpressionParser::parse(_predicate, ExtensionsCallbackNoop(), pExpCtx->getCollator()));
_expression = std::move(status.getValue());
} // namespace mongo