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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 <third_party/murmurhash3/MurmurHash3.h>
#include "mongo/base/init.h"
#include "mongo/db/bson/dotted_path_support.h"
#include "mongo/db/fts/fts_index_format.h"
#include "mongo/db/fts/fts_spec.h"
#include "mongo/db/server_options.h"
#include "mongo/util/hex.h"
#include "mongo/util/md5.hpp"
#include "mongo/util/str.h"
namespace mongo {
namespace fts {
using std::string;
using std::vector;
namespace dps = ::mongo::dotted_path_support;
namespace {
BSONObj nullObj;
BSONElement nullElt;
// New in textIndexVersion 2.
// If the term is longer than 32 characters, it may
// result in the generated key being too large
// for the index. In that case, we generate a 64-character key
// from the concatenation of the first 32 characters
// and the hex string of the murmur3 hash value of the entire
// term value.
const size_t termKeyPrefixLengthV2 = 32U;
// 128-bit hash value expressed in hex = 32 characters
const size_t termKeySuffixLengthV2 = 32U;
const size_t termKeyLengthV2 = termKeyPrefixLengthV2 + termKeySuffixLengthV2;
// TextIndexVersion 3.
// If the term is longer than 256 characters, it may
// result in the generated key being too large
// for the index. In that case, we generate a 256-character key
// from the concatenation of the first 224 characters
// and the hex string of the md5 hash value of the entire
// term value.
const size_t termKeyPrefixLengthV3 = 224U;
// 128-bit hash value expressed in hex = 32 characters
const size_t termKeySuffixLengthV3 = 32U;
const size_t termKeyLengthV3 = termKeyPrefixLengthV3 + termKeySuffixLengthV3;
/**
* Given an object being indexed, 'obj', and a path through 'obj', returns the corresponding BSON
* element, according to the indexing rules for the non-text fields of an FTS index key pattern.
*
* Specifically, throws a user assertion if an array is encountered while traversing the 'path'. It
* is not legal for there to be an array along the path of the non-text prefix or suffix fields of a
* text index, unless a particular array index is specified, as in "a.3".
*/
BSONElement extractNonFTSKeyElement(const BSONObj& obj, StringData path) {
BSONElementSet indexedElements;
const bool expandArrayOnTrailingField = true;
MultikeyComponents arrayComponents;
dps::extractAllElementsAlongPath(
obj, path, indexedElements, expandArrayOnTrailingField, &arrayComponents);
uassert(ErrorCodes::CannotBuildIndexKeys,
str::stream() << "Field '" << path
<< "' of text index contains an array in document: " << obj,
arrayComponents.empty());
// Since there aren't any arrays, there cannot be more than one extracted element on 'path'.
invariant(indexedElements.size() <= 1U);
return indexedElements.empty() ? nullElt : *indexedElements.begin();
}
} // namespace
MONGO_INITIALIZER(FTSIndexFormat)(InitializerContext* context) {
BSONObjBuilder b;
b.appendNull("");
nullObj = b.obj();
nullElt = nullObj.firstElement();
}
void FTSIndexFormat::getKeys(SharedBufferFragmentBuilder& pooledBufferBuilder,
const FTSSpec& spec,
const BSONObj& obj,
KeyStringSet* keys,
KeyString::Version keyStringVersion,
Ordering ordering,
const boost::optional<RecordId>& id) {
int extraSize = 0;
vector<BSONElement> extrasBefore;
vector<BSONElement> extrasAfter;
// Compute the non FTS key elements for the prefix.
for (unsigned i = 0; i < spec.numExtraBefore(); i++) {
auto indexedElement = extractNonFTSKeyElement(obj, spec.extraBefore(i));
extrasBefore.push_back(indexedElement);
extraSize += indexedElement.size();
}
// Compute the non FTS key elements for the suffix.
for (unsigned i = 0; i < spec.numExtraAfter(); i++) {
auto indexedElement = extractNonFTSKeyElement(obj, spec.extraAfter(i));
extrasAfter.push_back(indexedElement);
extraSize += indexedElement.size();
}
TermFrequencyMap term_freqs;
spec.scoreDocument(obj, &term_freqs);
auto sequence = keys->extract_sequence();
for (TermFrequencyMap::const_iterator i = term_freqs.begin(); i != term_freqs.end(); ++i) {
const string& term = i->first;
double weight = i->second;
KeyString::PooledBuilder keyString(pooledBufferBuilder, keyStringVersion, ordering);
for (const auto& elem : extrasBefore) {
keyString.appendBSONElement(elem);
}
_appendIndexKey(keyString, weight, term, spec.getTextIndexVersion());
for (const auto& elem : extrasAfter) {
keyString.appendBSONElement(elem);
}
if (id) {
keyString.appendRecordId(*id);
}
sequence.push_back(keyString.release());
}
keys->adopt_sequence(std::move(sequence));
}
BSONObj FTSIndexFormat::getIndexKey(double weight,
const string& term,
const BSONObj& indexPrefix,
TextIndexVersion textIndexVersion) {
BSONObjBuilder b;
BSONObjIterator i(indexPrefix);
while (i.more()) {
b.appendAs(i.next(), "");
}
KeyString::Builder keyString(KeyString::Version::kLatestVersion, KeyString::ALL_ASCENDING);
_appendIndexKey(keyString, weight, term, textIndexVersion);
auto key = KeyString::toBson(keyString, KeyString::ALL_ASCENDING);
return b.appendElements(key).obj();
}
template <typename KeyStringBuilder>
void FTSIndexFormat::_appendIndexKey(KeyStringBuilder& keyString,
double weight,
const string& term,
TextIndexVersion textIndexVersion) {
invariant(weight >= 0 && weight <= MAX_WEIGHT); // FTSmaxweight = defined in fts_header
// Terms are added to index key verbatim.
if (TEXT_INDEX_VERSION_1 == textIndexVersion) {
keyString.appendString(term);
}
// See comments at the top of file for termKeyPrefixLengthV2.
// Apply hash for text index version 2 to long terms (longer than 32 characters).
else if (TEXT_INDEX_VERSION_2 == textIndexVersion) {
if (term.size() <= termKeyPrefixLengthV2) {
keyString.appendString(term);
} else {
union {
uint64_t hash[2];
char data[16];
} t;
uint32_t seed = 0;
MurmurHash3_x64_128(term.data(), term.size(), seed, t.hash);
string keySuffix = hexblob::encodeLower(t.data, sizeof(t.data));
invariant(termKeySuffixLengthV2 == keySuffix.size());
keyString.appendString(term.substr(0, termKeyPrefixLengthV2) + keySuffix);
}
} else {
invariant(TEXT_INDEX_VERSION_3 == textIndexVersion);
if (term.size() <= termKeyPrefixLengthV3) {
keyString.appendString(term);
} else {
string keySuffix = md5simpledigest(term);
invariant(termKeySuffixLengthV3 == keySuffix.size());
keyString.appendString(term.substr(0, termKeyPrefixLengthV3) + keySuffix);
}
}
keyString.appendNumberDouble(weight);
}
} // namespace fts
} // namespace mongo
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