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/**
* Copyright (C) 2021-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/pipeline/change_stream_filter_helpers.h"
#include "mongo/db/bson/bson_helper.h"
#include "mongo/db/matcher/expression_always_boolean.h"
#include "mongo/db/matcher/expression_parser.h"
#include "mongo/db/pipeline/change_stream_rewrite_helpers.h"
#include "mongo/db/pipeline/document_source_change_stream.h"
#include "mongo/db/pipeline/pipeline.h"
namespace mongo {
namespace change_stream_filter {
std::unique_ptr<MatchExpression> buildTsFilter(
const boost::intrusive_ptr<ExpressionContext>& expCtx,
Timestamp startFromInclusive,
const MatchExpression* userMatch) {
return MatchExpressionParser::parseAndNormalize(BSON("ts" << GTE << startFromInclusive),
expCtx);
}
std::unique_ptr<MatchExpression> buildNotFromMigrateFilter(
const boost::intrusive_ptr<ExpressionContext>& expCtx, const MatchExpression* userMatch) {
return MatchExpressionParser::parseAndNormalize(BSON("fromMigrate" << NE << true), expCtx);
}
std::unique_ptr<MatchExpression> buildOperationFilter(
const boost::intrusive_ptr<ExpressionContext>& expCtx, const MatchExpression* userMatch) {
// Regexes to match each of the necessary namespace components for the current stream type.
auto nsRegex = DocumentSourceChangeStream::getNsRegexForChangeStream(expCtx->ns);
auto collRegex = DocumentSourceChangeStream::getCollRegexForChangeStream(expCtx->ns);
auto cmdNsRegex = DocumentSourceChangeStream::getCmdNsRegexForChangeStream(expCtx->ns);
auto streamType = DocumentSourceChangeStream::getChangeStreamType(expCtx->ns);
/**
* IMPORTANT: Any new operationType added here must also add corresponding oplog rewrites in the
* file change_stream_rewrite_helpers.cpp. A number of the existing rewrite functions in that
* file rely upon an exhaustive list of all change stream events that are derived directly from
* the oplog. Without appropriate rewrite rules for the new event, the optimizer will assume
* that no oplog entry can ever match the user's filter, causing it to discard those events.
*/
// The standard event filter, before it is combined with the user filter, is as follows:
// {
// $or: [
// {ns: nsRegex, $nor: [{op: "n"}, {op: "c"}]}, // CRUD events
// {ns: cmdNsRegex, op: "c", $or: [ // Commands on relevant DB(s)
// {"o.drop": collRegex}, // Drops of relevant collection(s)
// {"o.renameCollection": nsRegex}, // Renames of relevant collection(s)
// {"o.renameCollection": {$exists: true}, // Relevant collection was overwritten
// "o.to": nsRegex},
// {"o.dropDatabase": {$exists: true}} // Omitted for single-coll streams
// ]}
// ]
// }
// Top-level filter which will match against any of the categories of relevant events.
std::unique_ptr<ListOfMatchExpression> operationFilter = std::make_unique<OrMatchExpression>();
// (1) CRUD events on a monitored namespace.
auto crudEvents = BSON("ns" << BSONRegEx(nsRegex) << "$nor"
<< BSON_ARRAY(BSON("op"
<< "n")
<< BSON("op"
<< "c")));
// (2.1) The namespace for matching relevant commands.
auto cmdNsMatch = BSON("op"
<< "c"
<< "ns" << BSONRegEx(cmdNsRegex));
// (2.2) Commands that are run on a monitored database and/or collection.
auto dropEvent = BSON("o.drop" << BSONRegEx(collRegex));
auto dropDbEvent = BSON("o.dropDatabase" << BSON("$exists" << true));
auto renameFromEvent = BSON("o.renameCollection" << BSONRegEx(nsRegex));
auto renameToEvent =
BSON("o.renameCollection" << BSON("$exists" << true) << "o.to" << BSONRegEx(nsRegex));
auto orCmdEvents = std::make_unique<OrMatchExpression>();
orCmdEvents->add(MatchExpressionParser::parseAndNormalize(dropEvent, expCtx));
orCmdEvents->add(MatchExpressionParser::parseAndNormalize(renameFromEvent, expCtx));
orCmdEvents->add(MatchExpressionParser::parseAndNormalize(renameToEvent, expCtx));
// Omit dropDatabase on single-collection streams. While the stream will be invalidated before
// it sees this event, the user will incorrectly see it if they startAfter the invalidate.
if (streamType != DocumentSourceChangeStream::ChangeStreamType::kSingleCollection) {
orCmdEvents->add(MatchExpressionParser::parseAndNormalize(dropDbEvent, expCtx));
}
// (2.3) Commands must match the cmd namespace AND one of the event filters.
auto cmdEventsOnTargetDb = std::make_unique<AndMatchExpression>();
cmdEventsOnTargetDb->add(MatchExpressionParser::parseAndNormalize(cmdNsMatch, expCtx));
cmdEventsOnTargetDb->add(std::move(orCmdEvents));
// (3) Put together the final standard filter.
operationFilter->add(MatchExpressionParser::parseAndNormalize(crudEvents, expCtx));
operationFilter->add(std::move(cmdEventsOnTargetDb));
// (4) Apply the user's match filters to the standard event filter.
if (auto rewrittenMatch = change_stream_rewrite::rewriteFilterForFields(expCtx, userMatch)) {
operationFilter = std::make_unique<AndMatchExpression>(std::move(operationFilter), nullptr);
operationFilter->add(std::move(rewrittenMatch));
}
return operationFilter;
}
std::unique_ptr<MatchExpression> buildInvalidationFilter(
const boost::intrusive_ptr<ExpressionContext>& expCtx, const MatchExpression* userMatch) {
auto nss = expCtx->ns;
auto streamType = DocumentSourceChangeStream::getChangeStreamType(nss);
// A whole-cluster change stream is not invalidated by anything.
if (streamType == DocumentSourceChangeStream::ChangeStreamType::kAllChangesForCluster) {
return std::make_unique<AlwaysFalseMatchExpression>();
}
BSONArrayBuilder invalidatingCommands;
if (streamType == DocumentSourceChangeStream::ChangeStreamType::kSingleCollection) {
// A single-collection stream is invalidated by drop and rename events.
invalidatingCommands.append(BSON("o.drop" << nss.coll()));
invalidatingCommands.append(BSON("o.renameCollection" << nss.ns()));
invalidatingCommands.append(
BSON("o.renameCollection" << BSON("$exists" << true) << "o.to" << nss.ns()));
} else {
// For a whole-db streams, only 'dropDatabase' will cause an invalidation event.
invalidatingCommands.append(BSON("o.dropDatabase" << BSON("$exists" << true)));
}
// Match only against the target db's command namespace.
auto invalidatingFilter = BSON("op"
<< "c"
<< "ns" << nss.getCommandNS().ns() << "$or"
<< invalidatingCommands.arr());
return MatchExpressionParser::parseAndNormalize(invalidatingFilter, expCtx);
} // namespace change_stream_filter
std::unique_ptr<MatchExpression> buildTransactionFilter(
const boost::intrusive_ptr<ExpressionContext>& expCtx, const MatchExpression* userMatch) {
BSONObjBuilder applyOpsBuilder;
// "o.applyOps" stores the list of operations, so it must be an array.
applyOpsBuilder.append("op", "c");
applyOpsBuilder.append("o.applyOps",
BSON("$type"
<< "array"));
applyOpsBuilder.append("lsid", BSON("$exists" << true));
applyOpsBuilder.append("txnNumber", BSON("$exists" << true));
applyOpsBuilder.append("o.prepare", BSON("$not" << BSON("$eq" << true)));
applyOpsBuilder.append("o.partialTxn", BSON("$not" << BSON("$eq" << true)));
{
// Include this 'applyOps' if it has an operation with a matching namespace _or_ if it has a
// 'prevOpTime' link to another 'applyOps' command, indicating a multi-entry transaction.
BSONArrayBuilder orBuilder(applyOpsBuilder.subarrayStart("$or"));
{
{
BSONObjBuilder nsMatchBuilder(orBuilder.subobjStart());
nsMatchBuilder.append(
"o.applyOps.ns"_sd,
BSONRegEx(DocumentSourceChangeStream::getNsRegexForChangeStream(expCtx->ns)));
}
// The default repl::OpTime is the value used to indicate a null "prevOpTime" link.
orBuilder.append(BSON(repl::OplogEntry::kPrevWriteOpTimeInTransactionFieldName
<< BSON("$ne" << repl::OpTime().toBSON())));
}
}
auto applyOpsFilter = applyOpsBuilder.obj();
auto transactionFilter =
MatchExpressionParser::parseAndNormalize(BSON(OR(applyOpsFilter,
BSON("op"
<< "c"
<< "o.commitTransaction" << 1))),
expCtx);
// All events in a transaction share the same clusterTime, lsid, and txNumber values. If the
// user wishes to filter out events based on these values, it is possible to rewrite these
// filters to filter out entire applyOps and commitTransaction entries before they are unwound.
if (auto rewrittenMatch = change_stream_rewrite::rewriteFilterForFields(
expCtx, userMatch, {"clusterTime", "lsid", "txnNumber"})) {
auto transactionFilterWithUserMatch = std::make_unique<AndMatchExpression>();
transactionFilterWithUserMatch->add(std::move(transactionFilter));
transactionFilterWithUserMatch->add(std::move(rewrittenMatch));
return transactionFilterWithUserMatch;
}
return transactionFilter;
}
std::unique_ptr<MatchExpression> buildInternalOpFilter(
const boost::intrusive_ptr<ExpressionContext>& expCtx, const MatchExpression* userMatch) {
// Noop change events:
// - reshardBegin: A resharding operation begins.
// - reshardDoneCatchUp: "Catch up" phase of reshard operation completes.
std::vector<StringData> internalOpTypes = {"reshardBegin"_sd, "reshardDoneCatchUp"_sd};
// Noop change events that are only applicable when merging results on mongoS:
// - migrateChunkToNewShard: A chunk migrated to a shard that didn't have any chunks.
if (expCtx->inMongos || expCtx->needsMerge) {
internalOpTypes.push_back("migrateChunkToNewShard"_sd);
}
// Build the oplog filter to match the required internal op types.
BSONArrayBuilder internalOpTypeOrBuilder;
for (const auto& eventName : internalOpTypes) {
internalOpTypeOrBuilder.append(BSON("o2.type" << eventName));
}
internalOpTypeOrBuilder.done();
return MatchExpressionParser::parseAndNormalize(BSON("op"
<< "n"
<< "$or" << internalOpTypeOrBuilder.arr()),
expCtx);
}
} // namespace change_stream_filter
} // namespace mongo
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