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/**
* Copyright (C) 2013-2014 MongoDB 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
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* 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 <http://www.gnu.org/licenses/>.
*
* 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.
*/
#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kQuery
#include "mongo/platform/basic.h"
#include "mongo/db/query/get_executor.h"
#include <boost/optional.hpp>
#include <limits>
#include <memory>
#include "mongo/base/error_codes.h"
#include "mongo/base/parse_number.h"
#include "mongo/client/dbclientinterface.h"
#include "mongo/db/exec/cached_plan.h"
#include "mongo/db/exec/count.h"
#include "mongo/db/exec/delete.h"
#include "mongo/db/exec/eof.h"
#include "mongo/db/exec/group.h"
#include "mongo/db/exec/idhack.h"
#include "mongo/db/exec/multi_plan.h"
#include "mongo/db/exec/oplogstart.h"
#include "mongo/db/exec/projection.h"
#include "mongo/db/exec/shard_filter.h"
#include "mongo/db/exec/sort_key_generator.h"
#include "mongo/db/exec/subplan.h"
#include "mongo/db/exec/update.h"
#include "mongo/db/index/index_descriptor.h"
#include "mongo/db/index_names.h"
#include "mongo/db/matcher/extensions_callback_disallow_extensions.h"
#include "mongo/db/matcher/extensions_callback_noop.h"
#include "mongo/db/matcher/extensions_callback_real.h"
#include "mongo/db/ops/update_lifecycle.h"
#include "mongo/db/query/canonical_query.h"
#include "mongo/db/query/collation/collator_factory_interface.h"
#include "mongo/db/query/explain.h"
#include "mongo/db/query/index_bounds_builder.h"
#include "mongo/db/query/internal_plans.h"
#include "mongo/db/query/plan_cache.h"
#include "mongo/db/query/plan_executor.h"
#include "mongo/db/query/planner_access.h"
#include "mongo/db/query/planner_analysis.h"
#include "mongo/db/query/query_knobs.h"
#include "mongo/db/query/query_planner.h"
#include "mongo/db/query/query_planner_common.h"
#include "mongo/db/query/query_settings.h"
#include "mongo/db/query/stage_builder.h"
#include "mongo/db/repl/replication_coordinator_global.h"
#include "mongo/db/s/collection_metadata.h"
#include "mongo/db/s/collection_sharding_state.h"
#include "mongo/db/s/sharding_state.h"
#include "mongo/db/server_options.h"
#include "mongo/db/server_parameters.h"
#include "mongo/db/service_context.h"
#include "mongo/db/storage/oplog_hack.h"
#include "mongo/db/storage/storage_options.h"
#include "mongo/scripting/engine.h"
#include "mongo/stdx/memory.h"
#include "mongo/util/log.h"
#include "mongo/util/stringutils.h"
namespace mongo {
using std::unique_ptr;
using std::string;
using std::vector;
using stdx::make_unique;
// static
void filterAllowedIndexEntries(const AllowedIndicesFilter& allowedIndicesFilter,
std::vector<IndexEntry>* indexEntries) {
invariant(indexEntries);
// Filter index entries
// Check BSON objects in AllowedIndices::_indexKeyPatterns against IndexEntry::keyPattern.
// Removes IndexEntrys that do not match _indexKeyPatterns.
std::vector<IndexEntry> temp;
for (std::vector<IndexEntry>::const_iterator i = indexEntries->begin();
i != indexEntries->end();
++i) {
const IndexEntry& indexEntry = *i;
if (allowedIndicesFilter.allows(indexEntry)) {
// Copy index entry into temp vector if found in query settings.
temp.push_back(indexEntry);
}
}
// Update results.
temp.swap(*indexEntries);
}
namespace {
// The body is below in the "count hack" section but getExecutor calls it.
bool turnIxscanIntoCount(QuerySolution* soln);
} // namespace
void fillOutPlannerParams(OperationContext* opCtx,
Collection* collection,
CanonicalQuery* canonicalQuery,
QueryPlannerParams* plannerParams) {
// If it's not NULL, we may have indices. Access the catalog and fill out IndexEntry(s)
IndexCatalog::IndexIterator ii = collection->getIndexCatalog()->getIndexIterator(opCtx, false);
while (ii.more()) {
const IndexDescriptor* desc = ii.next();
IndexCatalogEntry* ice = ii.catalogEntry(desc);
plannerParams->indices.push_back(IndexEntry(desc->keyPattern(),
desc->getAccessMethodName(),
desc->isMultikey(opCtx),
ice->getMultikeyPaths(opCtx),
desc->isSparse(),
desc->unique(),
desc->indexName(),
ice->getFilterExpression(),
desc->infoObj(),
ice->getCollator()));
}
// If query supports index filters, filter params.indices by indices in query settings.
// Ignore index filters when it is possible to use the id-hack.
if (!IDHackStage::supportsQuery(collection, *canonicalQuery)) {
QuerySettings* querySettings = collection->infoCache()->getQuerySettings();
PlanCacheKey planCacheKey =
collection->infoCache()->getPlanCache()->computeKey(*canonicalQuery);
// Filter index catalog if index filters are specified for query.
// Also, signal to planner that application hint should be ignored.
if (boost::optional<AllowedIndicesFilter> allowedIndicesFilter =
querySettings->getAllowedIndicesFilter(planCacheKey)) {
filterAllowedIndexEntries(*allowedIndicesFilter, &plannerParams->indices);
plannerParams->indexFiltersApplied = true;
}
}
// We will not output collection scans unless there are no indexed solutions. NO_TABLE_SCAN
// overrides this behavior by not outputting a collscan even if there are no indexed
// solutions.
if (storageGlobalParams.noTableScan.load()) {
const string& ns = canonicalQuery->ns();
// There are certain cases where we ignore this restriction:
bool ignore = canonicalQuery->getQueryObj().isEmpty() ||
(string::npos != ns.find(".system.")) || (0 == ns.find("local."));
if (!ignore) {
plannerParams->options |= QueryPlannerParams::NO_TABLE_SCAN;
}
}
// If the caller wants a shard filter, make sure we're actually sharded.
if (plannerParams->options & QueryPlannerParams::INCLUDE_SHARD_FILTER) {
auto collMetadata =
CollectionShardingState::get(opCtx, canonicalQuery->nss())->getMetadata();
if (collMetadata) {
plannerParams->shardKey = collMetadata->getKeyPattern();
} else {
// If there's no metadata don't bother w/the shard filter since we won't know what
// the key pattern is anyway...
plannerParams->options &= ~QueryPlannerParams::INCLUDE_SHARD_FILTER;
}
}
if (internalQueryPlannerEnableIndexIntersection.load()) {
plannerParams->options |= QueryPlannerParams::INDEX_INTERSECTION;
}
plannerParams->options |= QueryPlannerParams::SPLIT_LIMITED_SORT;
// Doc-level locking storage engines cannot answer predicates implicitly via exact index
// bounds for index intersection plans, as this can lead to spurious matches.
//
// Such storage engines do not use the invalidation framework, and therefore
// have no need for KEEP_MUTATIONS.
if (supportsDocLocking()) {
plannerParams->options |= QueryPlannerParams::CANNOT_TRIM_IXISECT;
} else {
plannerParams->options |= QueryPlannerParams::KEEP_MUTATIONS;
}
// MMAPv1 storage engine should have snapshot() perform an index scan on _id rather than a
// collection scan since a collection scan on the MMAP storage engine can return duplicates
// or miss documents.
if (isMMAPV1()) {
plannerParams->options |= QueryPlannerParams::SNAPSHOT_USE_ID;
}
}
namespace {
struct PrepareExecutionResult {
PrepareExecutionResult(unique_ptr<CanonicalQuery> canonicalQuery,
unique_ptr<QuerySolution> querySolution,
unique_ptr<PlanStage> root)
: canonicalQuery(std::move(canonicalQuery)),
querySolution(std::move(querySolution)),
root(std::move(root)) {}
unique_ptr<CanonicalQuery> canonicalQuery;
unique_ptr<QuerySolution> querySolution;
unique_ptr<PlanStage> root;
};
/**
* Build an execution tree for the query described in 'canonicalQuery'.
*
* If an execution tree could be created, then returns a PrepareExecutionResult that wraps:
* - The CanonicalQuery describing the query operation. This may be equal to the original canonical
* query, or may be modified. This will never be null.
* - A QuerySolution, representing the associated query solution. This may be null, in certain
* circumstances where the constructed execution tree does not have an associated query solution.
* - A PlanStage, representing the root of the constructed execution tree. This will never be null.
*
* If an execution tree could not be created, returns an error Status.
*/
StatusWith<PrepareExecutionResult> prepareExecution(OperationContext* opCtx,
Collection* collection,
WorkingSet* ws,
unique_ptr<CanonicalQuery> canonicalQuery,
size_t plannerOptions) {
invariant(canonicalQuery);
unique_ptr<PlanStage> root;
unique_ptr<QuerySolution> querySolution;
// This can happen as we're called by internal clients as well.
if (NULL == collection) {
const string& ns = canonicalQuery->ns();
LOG(2) << "Collection " << ns << " does not exist."
<< " Using EOF plan: " << redact(canonicalQuery->toStringShort());
root = make_unique<EOFStage>(opCtx);
return PrepareExecutionResult(
std::move(canonicalQuery), std::move(querySolution), std::move(root));
}
// Fill out the planning params. We use these for both cached solutions and non-cached.
QueryPlannerParams plannerParams;
plannerParams.options = plannerOptions;
fillOutPlannerParams(opCtx, collection, canonicalQuery.get(), &plannerParams);
// If the canonical query does not have a user-specified collation, set it from the collection
// default.
if (canonicalQuery->getQueryRequest().getCollation().isEmpty() &&
collection->getDefaultCollator()) {
canonicalQuery->setCollator(collection->getDefaultCollator()->clone());
}
const IndexDescriptor* descriptor = collection->getIndexCatalog()->findIdIndex(opCtx);
// If we have an _id index we can use an idhack plan.
if (descriptor && IDHackStage::supportsQuery(collection, *canonicalQuery)) {
LOG(2) << "Using idhack: " << redact(canonicalQuery->toStringShort());
root = make_unique<IDHackStage>(opCtx, collection, canonicalQuery.get(), ws, descriptor);
// Might have to filter out orphaned docs.
if (plannerParams.options & QueryPlannerParams::INCLUDE_SHARD_FILTER) {
root = make_unique<ShardFilterStage>(
opCtx,
CollectionShardingState::get(opCtx, canonicalQuery->nss())->getMetadata(),
ws,
root.release());
}
// There might be a projection. The idhack stage will always fetch the full
// document, so we don't support covered projections. However, we might use the
// simple inclusion fast path.
if (NULL != canonicalQuery->getProj()) {
ProjectionStageParams params(ExtensionsCallbackReal(opCtx, &collection->ns()));
params.projObj = canonicalQuery->getProj()->getProjObj();
params.collator = canonicalQuery->getCollator();
// Add a SortKeyGeneratorStage if there is a $meta sortKey projection.
if (canonicalQuery->getProj()->wantSortKey()) {
root = make_unique<SortKeyGeneratorStage>(
opCtx,
root.release(),
ws,
canonicalQuery->getQueryRequest().getSort(),
canonicalQuery->getQueryRequest().getFilter(),
canonicalQuery->getCollator());
}
// Stuff the right data into the params depending on what proj impl we use.
if (canonicalQuery->getProj()->requiresDocument() ||
canonicalQuery->getProj()->wantIndexKey() ||
canonicalQuery->getProj()->wantSortKey() ||
canonicalQuery->getProj()->hasDottedFieldPath()) {
params.fullExpression = canonicalQuery->root();
params.projImpl = ProjectionStageParams::NO_FAST_PATH;
} else {
params.projImpl = ProjectionStageParams::SIMPLE_DOC;
}
root = make_unique<ProjectionStage>(opCtx, params, ws, root.release());
}
return PrepareExecutionResult(
std::move(canonicalQuery), std::move(querySolution), std::move(root));
}
// Tailable: If the query requests tailable the collection must be capped.
if (canonicalQuery->getQueryRequest().isTailable()) {
if (!collection->isCapped()) {
return Status(ErrorCodes::BadValue,
"error processing query: " + canonicalQuery->toString() +
" tailable cursor requested on non capped collection");
}
}
// Try to look up a cached solution for the query.
CachedSolution* rawCS;
if (PlanCache::shouldCacheQuery(*canonicalQuery) &&
collection->infoCache()->getPlanCache()->get(*canonicalQuery, &rawCS).isOK()) {
// We have a CachedSolution. Have the planner turn it into a QuerySolution.
unique_ptr<CachedSolution> cs(rawCS);
QuerySolution* qs;
Status status = QueryPlanner::planFromCache(*canonicalQuery, plannerParams, *cs, &qs);
if (status.isOK()) {
if ((plannerParams.options & QueryPlannerParams::IS_COUNT) && turnIxscanIntoCount(qs)) {
LOG(2) << "Using fast count: " << redact(canonicalQuery->toStringShort());
}
PlanStage* rawRoot;
verify(StageBuilder::build(opCtx, collection, *canonicalQuery, *qs, ws, &rawRoot));
// Add a CachedPlanStage on top of the previous root.
//
// 'decisionWorks' is used to determine whether the existing cache entry should
// be evicted, and the query replanned.
root = make_unique<CachedPlanStage>(opCtx,
collection,
ws,
canonicalQuery.get(),
plannerParams,
cs->decisionWorks,
rawRoot);
querySolution.reset(qs);
return PrepareExecutionResult(
std::move(canonicalQuery), std::move(querySolution), std::move(root));
}
}
if (internalQueryPlanOrChildrenIndependently.load() &&
SubplanStage::canUseSubplanning(*canonicalQuery)) {
LOG(2) << "Running query as sub-queries: " << redact(canonicalQuery->toStringShort());
root =
make_unique<SubplanStage>(opCtx, collection, ws, plannerParams, canonicalQuery.get());
return PrepareExecutionResult(
std::move(canonicalQuery), std::move(querySolution), std::move(root));
}
vector<QuerySolution*> solutions;
Status status = QueryPlanner::plan(*canonicalQuery, plannerParams, &solutions);
if (!status.isOK()) {
return Status(ErrorCodes::BadValue,
"error processing query: " + canonicalQuery->toString() +
" planner returned error: " + status.reason());
}
// We cannot figure out how to answer the query. Perhaps it requires an index
// we do not have?
if (0 == solutions.size()) {
return Status(ErrorCodes::BadValue,
str::stream() << "error processing query: " << canonicalQuery->toString()
<< " No query solutions");
}
// See if one of our solutions is a fast count hack in disguise.
if (plannerParams.options & QueryPlannerParams::IS_COUNT) {
for (size_t i = 0; i < solutions.size(); ++i) {
if (turnIxscanIntoCount(solutions[i])) {
// Great, we can use solutions[i]. Clean up the other QuerySolution(s).
for (size_t j = 0; j < solutions.size(); ++j) {
if (j != i) {
delete solutions[j];
}
}
// We're not going to cache anything that's fast count.
PlanStage* rawRoot;
verify(StageBuilder::build(
opCtx, collection, *canonicalQuery, *solutions[i], ws, &rawRoot));
root.reset(rawRoot);
LOG(2) << "Using fast count: " << redact(canonicalQuery->toStringShort())
<< ", planSummary: " << redact(Explain::getPlanSummary(root.get()));
querySolution.reset(solutions[i]);
return PrepareExecutionResult(
std::move(canonicalQuery), std::move(querySolution), std::move(root));
}
}
}
if (1 == solutions.size()) {
// Only one possible plan. Run it. Build the stages from the solution.
PlanStage* rawRoot;
verify(
StageBuilder::build(opCtx, collection, *canonicalQuery, *solutions[0], ws, &rawRoot));
root.reset(rawRoot);
LOG(2) << "Only one plan is available; it will be run but will not be cached. "
<< redact(canonicalQuery->toStringShort())
<< ", planSummary: " << redact(Explain::getPlanSummary(root.get()));
querySolution.reset(solutions[0]);
return PrepareExecutionResult(
std::move(canonicalQuery), std::move(querySolution), std::move(root));
} else {
// Many solutions. Create a MultiPlanStage to pick the best, update the cache,
// and so on. The working set will be shared by all candidate plans.
auto multiPlanStage = make_unique<MultiPlanStage>(opCtx, collection, canonicalQuery.get());
for (size_t ix = 0; ix < solutions.size(); ++ix) {
if (solutions[ix]->cacheData.get()) {
solutions[ix]->cacheData->indexFilterApplied = plannerParams.indexFiltersApplied;
}
// version of StageBuild::build when WorkingSet is shared
PlanStage* nextPlanRoot;
verify(StageBuilder::build(
opCtx, collection, *canonicalQuery, *solutions[ix], ws, &nextPlanRoot));
// Owns none of the arguments
multiPlanStage->addPlan(solutions[ix], nextPlanRoot, ws);
}
root = std::move(multiPlanStage);
return PrepareExecutionResult(
std::move(canonicalQuery), std::move(querySolution), std::move(root));
}
}
} // namespace
StatusWith<unique_ptr<PlanExecutor>> getExecutor(OperationContext* opCtx,
Collection* collection,
unique_ptr<CanonicalQuery> canonicalQuery,
PlanExecutor::YieldPolicy yieldPolicy,
size_t plannerOptions) {
unique_ptr<WorkingSet> ws = make_unique<WorkingSet>();
StatusWith<PrepareExecutionResult> executionResult =
prepareExecution(opCtx, collection, ws.get(), std::move(canonicalQuery), plannerOptions);
if (!executionResult.isOK()) {
return executionResult.getStatus();
}
invariant(executionResult.getValue().root);
// We must have a tree of stages in order to have a valid plan executor, but the query
// solution may be null.
return PlanExecutor::make(opCtx,
std::move(ws),
std::move(executionResult.getValue().root),
std::move(executionResult.getValue().querySolution),
std::move(executionResult.getValue().canonicalQuery),
collection,
yieldPolicy);
}
//
// Find
//
namespace {
/**
* Returns true if 'me' is a GTE or GE predicate over the "ts" field.
* Such predicates can be used for the oplog start hack.
*/
bool isOplogTsPred(const mongo::MatchExpression* me) {
if (mongo::MatchExpression::GT != me->matchType() &&
mongo::MatchExpression::GTE != me->matchType()) {
return false;
}
return mongoutils::str::equals(me->path().rawData(), "ts");
}
mongo::BSONElement extractOplogTsOptime(const mongo::MatchExpression* me) {
invariant(isOplogTsPred(me));
return static_cast<const mongo::ComparisonMatchExpression*>(me)->getData();
}
StatusWith<unique_ptr<PlanExecutor>> getOplogStartHack(OperationContext* opCtx,
Collection* collection,
unique_ptr<CanonicalQuery> cq) {
invariant(collection);
invariant(cq.get());
if (!collection->isCapped()) {
return Status(ErrorCodes::BadValue,
"OplogReplay cursor requested on non-capped collection");
}
// If the canonical query does not have a user-specified collation, set it from the collection
// default.
if (cq->getQueryRequest().getCollation().isEmpty() && collection->getDefaultCollator()) {
cq->setCollator(collection->getDefaultCollator()->clone());
}
// A query can only do oplog start finding if it has a top-level $gt or $gte predicate over
// the "ts" field (the operation's timestamp). Find that predicate and pass it to
// the OplogStart stage.
MatchExpression* tsExpr = NULL;
if (MatchExpression::AND == cq->root()->matchType()) {
// The query has an AND at the top-level. See if any of the children
// of the AND are $gt or $gte predicates over 'ts'.
for (size_t i = 0; i < cq->root()->numChildren(); ++i) {
MatchExpression* me = cq->root()->getChild(i);
if (isOplogTsPred(me)) {
tsExpr = me;
break;
}
}
} else if (isOplogTsPred(cq->root())) {
// The root of the tree is a $gt or $gte predicate over 'ts'.
tsExpr = cq->root();
}
if (NULL == tsExpr) {
return Status(ErrorCodes::OplogOperationUnsupported,
"OplogReplay query does not contain top-level "
"$gt or $gte over the 'ts' field.");
}
boost::optional<RecordId> startLoc = boost::none;
// See if the RecordStore supports the oplogStartHack
const BSONElement tsElem = extractOplogTsOptime(tsExpr);
if (tsElem.type() == bsonTimestamp) {
StatusWith<RecordId> goal = oploghack::keyForOptime(tsElem.timestamp());
if (goal.isOK()) {
startLoc = collection->getRecordStore()->oplogStartHack(opCtx, goal.getValue());
}
}
if (startLoc) {
LOG(3) << "Using direct oplog seek";
} else {
LOG(3) << "Using OplogStart stage";
// Fallback to trying the OplogStart stage.
unique_ptr<WorkingSet> oplogws = make_unique<WorkingSet>();
unique_ptr<OplogStart> stage =
make_unique<OplogStart>(opCtx, collection, tsExpr, oplogws.get());
// Takes ownership of oplogws and stage.
auto statusWithPlanExecutor = PlanExecutor::make(
opCtx, std::move(oplogws), std::move(stage), collection, PlanExecutor::YIELD_AUTO);
invariant(statusWithPlanExecutor.isOK());
unique_ptr<PlanExecutor> exec = std::move(statusWithPlanExecutor.getValue());
// The stage returns a RecordId of where to start.
startLoc = RecordId();
PlanExecutor::ExecState state = exec->getNext(NULL, startLoc.get_ptr());
// This is normal. The start of the oplog is the beginning of the collection.
if (PlanExecutor::IS_EOF == state) {
return getExecutor(opCtx, collection, std::move(cq), PlanExecutor::YIELD_AUTO);
}
// This is not normal. An error was encountered.
if (PlanExecutor::ADVANCED != state) {
return Status(ErrorCodes::InternalError, "quick oplog start location had error...?");
}
}
// Build our collection scan...
CollectionScanParams params;
params.collection = collection;
params.start = *startLoc;
params.direction = CollectionScanParams::FORWARD;
params.tailable = cq->getQueryRequest().isTailable();
// If the query is just tsExpr, we know that every document in the collection after the first
// matching one must also match. To avoid wasting time running the match expression on every
// document to be returned, we tell the CollectionScan stage to stop applying the filter once it
// finds the first match.
if (cq->root() == tsExpr) {
params.stopApplyingFilterAfterFirstMatch = true;
}
unique_ptr<WorkingSet> ws = make_unique<WorkingSet>();
unique_ptr<CollectionScan> cs =
make_unique<CollectionScan>(opCtx, params, ws.get(), cq->root());
// Takes ownership of 'ws', 'cs', and 'cq'.
return PlanExecutor::make(
opCtx, std::move(ws), std::move(cs), std::move(cq), collection, PlanExecutor::YIELD_AUTO);
}
} // namespace
StatusWith<unique_ptr<PlanExecutor>> getExecutorFind(OperationContext* opCtx,
Collection* collection,
const NamespaceString& nss,
unique_ptr<CanonicalQuery> canonicalQuery,
PlanExecutor::YieldPolicy yieldPolicy) {
if (NULL != collection && canonicalQuery->getQueryRequest().isOplogReplay()) {
return getOplogStartHack(opCtx, collection, std::move(canonicalQuery));
}
size_t options = QueryPlannerParams::DEFAULT;
if (ShardingState::get(opCtx)->needCollectionMetadata(opCtx, nss.ns())) {
options |= QueryPlannerParams::INCLUDE_SHARD_FILTER;
}
return getExecutor(
opCtx, collection, std::move(canonicalQuery), PlanExecutor::YIELD_AUTO, options);
}
namespace {
/**
* Wrap the specified 'root' plan stage in a ProjectionStage. Does not take ownership of any
* arguments other than root.
*
* If the projection was valid, then return Status::OK() with a pointer to the newly created
* ProjectionStage. Otherwise, return a status indicating the error reason.
*/
StatusWith<unique_ptr<PlanStage>> applyProjection(OperationContext* opCtx,
const NamespaceString& nsString,
CanonicalQuery* cq,
const BSONObj& proj,
bool allowPositional,
WorkingSet* ws,
unique_ptr<PlanStage> root) {
invariant(!proj.isEmpty());
ParsedProjection* rawParsedProj;
Status ppStatus = ParsedProjection::make(
proj.getOwned(), cq->root(), &rawParsedProj, ExtensionsCallbackDisallowExtensions());
if (!ppStatus.isOK()) {
return ppStatus;
}
unique_ptr<ParsedProjection> pp(rawParsedProj);
// ProjectionExec requires the MatchDetails from the query expression when the projection
// uses the positional operator. Since the query may no longer match the newly-updated
// document, we forbid this case.
if (!allowPositional && pp->requiresMatchDetails()) {
return {ErrorCodes::BadValue,
"cannot use a positional projection and return the new document"};
}
// $meta sortKey is not allowed to be projected in findAndModify commands.
if (pp->wantSortKey()) {
return {ErrorCodes::BadValue,
"Cannot use a $meta sortKey projection in findAndModify commands."};
}
ProjectionStageParams params(ExtensionsCallbackReal(opCtx, &nsString));
params.projObj = proj;
params.collator = cq->getCollator();
params.fullExpression = cq->root();
return {make_unique<ProjectionStage>(opCtx, params, ws, root.release())};
}
} // namespace
//
// Delete
//
StatusWith<unique_ptr<PlanExecutor>> getExecutorDelete(OperationContext* opCtx,
OpDebug* opDebug,
Collection* collection,
ParsedDelete* parsedDelete) {
const DeleteRequest* request = parsedDelete->getRequest();
const NamespaceString& nss(request->getNamespaceString());
if (!request->isGod()) {
if (nss.isSystem()) {
uassert(12050, "cannot delete from system namespace", legalClientSystemNS(nss.ns()));
}
if (nss.isVirtualized()) {
log() << "cannot delete from a virtual collection: " << nss;
uasserted(10100, "cannot delete from a virtual collection");
}
}
if (collection && collection->isCapped()) {
return Status(ErrorCodes::IllegalOperation,
str::stream() << "cannot remove from a capped collection: " << nss.ns());
}
bool userInitiatedWritesAndNotPrimary = opCtx->writesAreReplicated() &&
!repl::getGlobalReplicationCoordinator()->canAcceptWritesFor(opCtx, nss);
if (userInitiatedWritesAndNotPrimary) {
return Status(ErrorCodes::PrimarySteppedDown,
str::stream() << "Not primary while removing from " << nss.ns());
}
DeleteStageParams deleteStageParams;
deleteStageParams.isMulti = request->isMulti();
deleteStageParams.fromMigrate = request->isFromMigrate();
deleteStageParams.isExplain = request->isExplain();
deleteStageParams.returnDeleted = request->shouldReturnDeleted();
deleteStageParams.sort = request->getSort();
deleteStageParams.opDebug = opDebug;
unique_ptr<WorkingSet> ws = make_unique<WorkingSet>();
const PlanExecutor::YieldPolicy policy = parsedDelete->yieldPolicy();
if (!parsedDelete->hasParsedQuery()) {
// This is the idhack fast-path for getting a PlanExecutor without doing the work
// to create a CanonicalQuery.
const BSONObj& unparsedQuery = request->getQuery();
if (!collection) {
// Treat collections that do not exist as empty collections. Note that the explain
// reporting machinery always assumes that the root stage for a delete operation is
// a DeleteStage, so in this case we put a DeleteStage on top of an EOFStage.
LOG(2) << "Collection " << nss.ns() << " does not exist."
<< " Using EOF stage: " << redact(unparsedQuery);
auto deleteStage = make_unique<DeleteStage>(
opCtx, deleteStageParams, ws.get(), nullptr, new EOFStage(opCtx));
return PlanExecutor::make(opCtx, std::move(ws), std::move(deleteStage), nss, policy);
}
const IndexDescriptor* descriptor = collection->getIndexCatalog()->findIdIndex(opCtx);
// Construct delete request collator.
std::unique_ptr<CollatorInterface> collator;
if (!request->getCollation().isEmpty()) {
auto statusWithCollator = CollatorFactoryInterface::get(opCtx->getServiceContext())
->makeFromBSON(request->getCollation());
if (!statusWithCollator.isOK()) {
return statusWithCollator.getStatus();
}
collator = std::move(statusWithCollator.getValue());
}
const bool hasCollectionDefaultCollation = request->getCollation().isEmpty() ||
CollatorInterface::collatorsMatch(collator.get(), collection->getDefaultCollator());
if (descriptor && CanonicalQuery::isSimpleIdQuery(unparsedQuery) &&
request->getProj().isEmpty() && hasCollectionDefaultCollation) {
LOG(2) << "Using idhack: " << redact(unparsedQuery);
PlanStage* idHackStage = new IDHackStage(
opCtx, collection, unparsedQuery["_id"].wrap(), ws.get(), descriptor);
unique_ptr<DeleteStage> root = make_unique<DeleteStage>(
opCtx, deleteStageParams, ws.get(), collection, idHackStage);
return PlanExecutor::make(opCtx, std::move(ws), std::move(root), collection, policy);
}
// If we're here then we don't have a parsed query, but we're also not eligible for
// the idhack fast path. We need to force canonicalization now.
Status cqStatus = parsedDelete->parseQueryToCQ();
if (!cqStatus.isOK()) {
return cqStatus;
}
}
// This is the regular path for when we have a CanonicalQuery.
unique_ptr<CanonicalQuery> cq(parsedDelete->releaseParsedQuery());
const size_t defaultPlannerOptions = 0;
StatusWith<PrepareExecutionResult> executionResult =
prepareExecution(opCtx, collection, ws.get(), std::move(cq), defaultPlannerOptions);
if (!executionResult.isOK()) {
return executionResult.getStatus();
}
cq = std::move(executionResult.getValue().canonicalQuery);
unique_ptr<QuerySolution> querySolution = std::move(executionResult.getValue().querySolution);
unique_ptr<PlanStage> root = std::move(executionResult.getValue().root);
deleteStageParams.canonicalQuery = cq.get();
invariant(root);
root = make_unique<DeleteStage>(opCtx, deleteStageParams, ws.get(), collection, root.release());
if (!request->getProj().isEmpty()) {
invariant(request->shouldReturnDeleted());
const bool allowPositional = true;
StatusWith<unique_ptr<PlanStage>> projStatus = applyProjection(
opCtx, nss, cq.get(), request->getProj(), allowPositional, ws.get(), std::move(root));
if (!projStatus.isOK()) {
return projStatus.getStatus();
}
root = std::move(projStatus.getValue());
}
// We must have a tree of stages in order to have a valid plan executor, but the query
// solution may be null.
return PlanExecutor::make(opCtx,
std::move(ws),
std::move(root),
std::move(querySolution),
std::move(cq),
collection,
policy);
}
//
// Update
//
namespace {
// TODO: Make this a function on NamespaceString, or make it cleaner.
inline void validateUpdate(const char* ns, const BSONObj& updateobj, const BSONObj& patternOrig) {
uassert(10155, "cannot update reserved $ collection", strchr(ns, '$') == 0);
if (strstr(ns, ".system.")) {
/* dm: it's very important that system.indexes is never updated as IndexDetails
has pointers into it */
uassert(10156,
str::stream() << "cannot update system collection: " << ns << " q: " << patternOrig
<< " u: "
<< updateobj,
legalClientSystemNS(ns));
}
}
} // namespace
StatusWith<unique_ptr<PlanExecutor>> getExecutorUpdate(OperationContext* opCtx,
OpDebug* opDebug,
Collection* collection,
ParsedUpdate* parsedUpdate) {
const UpdateRequest* request = parsedUpdate->getRequest();
UpdateDriver* driver = parsedUpdate->getDriver();
const NamespaceString& nsString = request->getNamespaceString();
UpdateLifecycle* lifecycle = request->getLifecycle();
validateUpdate(nsString.ns().c_str(), request->getUpdates(), request->getQuery());
// If there is no collection and this is an upsert, callers are supposed to create
// the collection prior to calling this method. Explain, however, will never do
// collection or database creation.
if (!collection && request->isUpsert()) {
invariant(request->isExplain());
}
// If the parsed update does not have a user-specified collation, set it from the collection
// default.
if (collection && parsedUpdate->getRequest()->getCollation().isEmpty() &&
collection->getDefaultCollator()) {
parsedUpdate->setCollator(collection->getDefaultCollator()->clone());
}
// TODO: This seems a bit circuitious.
if (opDebug) {
opDebug->updateobj = request->getUpdates();
}
// If this is a user-issued update, then we want to return an error: you cannot perform
// writes on a secondary. If this is an update to a secondary from the replication system,
// however, then we make an exception and let the write proceed.
bool userInitiatedWritesAndNotPrimary = opCtx->writesAreReplicated() &&
!repl::getGlobalReplicationCoordinator()->canAcceptWritesFor(opCtx, nsString);
if (userInitiatedWritesAndNotPrimary) {
return Status(ErrorCodes::PrimarySteppedDown,
str::stream() << "Not primary while performing update on " << nsString.ns());
}
if (lifecycle) {
lifecycle->setCollection(collection);
driver->refreshIndexKeys(lifecycle->getIndexKeys(opCtx));
}
const PlanExecutor::YieldPolicy policy = parsedUpdate->yieldPolicy();
unique_ptr<WorkingSet> ws = make_unique<WorkingSet>();
UpdateStageParams updateStageParams(request, driver, opDebug);
if (!parsedUpdate->hasParsedQuery()) {
// This is the idhack fast-path for getting a PlanExecutor without doing the work
// to create a CanonicalQuery.
const BSONObj& unparsedQuery = request->getQuery();
if (!collection) {
// Treat collections that do not exist as empty collections. Note that the explain
// reporting machinery always assumes that the root stage for an update operation is
// an UpdateStage, so in this case we put an UpdateStage on top of an EOFStage.
LOG(2) << "Collection " << nsString.ns() << " does not exist."
<< " Using EOF stage: " << redact(unparsedQuery);
auto updateStage = make_unique<UpdateStage>(
opCtx, updateStageParams, ws.get(), collection, new EOFStage(opCtx));
return PlanExecutor::make(
opCtx, std::move(ws), std::move(updateStage), nsString, policy);
}
const IndexDescriptor* descriptor = collection->getIndexCatalog()->findIdIndex(opCtx);
const bool hasCollectionDefaultCollation = CollatorInterface::collatorsMatch(
parsedUpdate->getCollator(), collection->getDefaultCollator());
if (descriptor && CanonicalQuery::isSimpleIdQuery(unparsedQuery) &&
request->getProj().isEmpty() && hasCollectionDefaultCollation) {
LOG(2) << "Using idhack: " << redact(unparsedQuery);
PlanStage* idHackStage = new IDHackStage(
opCtx, collection, unparsedQuery["_id"].wrap(), ws.get(), descriptor);
unique_ptr<UpdateStage> root = make_unique<UpdateStage>(
opCtx, updateStageParams, ws.get(), collection, idHackStage);
return PlanExecutor::make(opCtx, std::move(ws), std::move(root), collection, policy);
}
// If we're here then we don't have a parsed query, but we're also not eligible for
// the idhack fast path. We need to force canonicalization now.
Status cqStatus = parsedUpdate->parseQueryToCQ();
if (!cqStatus.isOK()) {
return cqStatus;
}
}
// This is the regular path for when we have a CanonicalQuery.
unique_ptr<CanonicalQuery> cq(parsedUpdate->releaseParsedQuery());
const size_t defaultPlannerOptions = 0;
StatusWith<PrepareExecutionResult> executionResult =
prepareExecution(opCtx, collection, ws.get(), std::move(cq), defaultPlannerOptions);
if (!executionResult.isOK()) {
return executionResult.getStatus();
}
cq = std::move(executionResult.getValue().canonicalQuery);
unique_ptr<QuerySolution> querySolution = std::move(executionResult.getValue().querySolution);
unique_ptr<PlanStage> root = std::move(executionResult.getValue().root);
invariant(root);
updateStageParams.canonicalQuery = cq.get();
root = stdx::make_unique<UpdateStage>(
opCtx, updateStageParams, ws.get(), collection, root.release());
if (!request->getProj().isEmpty()) {
invariant(request->shouldReturnAnyDocs());
// If the plan stage is to return the newly-updated version of the documents, then it
// is invalid to use a positional projection because the query expression need not
// match the array element after the update has been applied.
const bool allowPositional = request->shouldReturnOldDocs();
StatusWith<unique_ptr<PlanStage>> projStatus = applyProjection(opCtx,
nsString,
cq.get(),
request->getProj(),
allowPositional,
ws.get(),
std::move(root));
if (!projStatus.isOK()) {
return projStatus.getStatus();
}
root = std::move(projStatus.getValue());
}
// We must have a tree of stages in order to have a valid plan executor, but the query
// solution may be null. Takes ownership of all args other than 'collection' and 'opCtx'
return PlanExecutor::make(opCtx,
std::move(ws),
std::move(root),
std::move(querySolution),
std::move(cq),
collection,
policy);
}
//
// Group
//
StatusWith<unique_ptr<PlanExecutor>> getExecutorGroup(OperationContext* opCtx,
Collection* collection,
const GroupRequest& request,
PlanExecutor::YieldPolicy yieldPolicy) {
if (!getGlobalScriptEngine()) {
return Status(ErrorCodes::BadValue, "server-side JavaScript execution is disabled");
}
unique_ptr<WorkingSet> ws = make_unique<WorkingSet>();
if (!collection) {
// Treat collections that do not exist as empty collections. Note that the explain
// reporting machinery always assumes that the root stage for a group operation is a
// GroupStage, so in this case we put a GroupStage on top of an EOFStage.
unique_ptr<PlanStage> root =
make_unique<GroupStage>(opCtx, request, ws.get(), new EOFStage(opCtx));
return PlanExecutor::make(opCtx, std::move(ws), std::move(root), request.ns, yieldPolicy);
}
const NamespaceString nss(request.ns);
auto qr = stdx::make_unique<QueryRequest>(nss);
qr->setFilter(request.query);
qr->setCollation(request.collation);
qr->setExplain(request.explain);
const ExtensionsCallbackReal extensionsCallback(opCtx, &nss);
auto statusWithCQ = CanonicalQuery::canonicalize(opCtx, std::move(qr), extensionsCallback);
if (!statusWithCQ.isOK()) {
return statusWithCQ.getStatus();
}
unique_ptr<CanonicalQuery> canonicalQuery = std::move(statusWithCQ.getValue());
const size_t defaultPlannerOptions = 0;
StatusWith<PrepareExecutionResult> executionResult = prepareExecution(
opCtx, collection, ws.get(), std::move(canonicalQuery), defaultPlannerOptions);
if (!executionResult.isOK()) {
return executionResult.getStatus();
}
canonicalQuery = std::move(executionResult.getValue().canonicalQuery);
unique_ptr<QuerySolution> querySolution = std::move(executionResult.getValue().querySolution);
unique_ptr<PlanStage> root = std::move(executionResult.getValue().root);
invariant(root);
root = make_unique<GroupStage>(opCtx, request, ws.get(), root.release());
// We must have a tree of stages in order to have a valid plan executor, but the query
// solution may be null. Takes ownership of all args other than 'collection'.
return PlanExecutor::make(opCtx,
std::move(ws),
std::move(root),
std::move(querySolution),
std::move(canonicalQuery),
collection,
yieldPolicy);
}
//
// Count hack
//
namespace {
/**
* Returns 'true' if the provided solution 'soln' can be rewritten to use
* a fast counting stage. Mutates the tree in 'soln->root'.
*
* Otherwise, returns 'false'.
*/
bool turnIxscanIntoCount(QuerySolution* soln) {
QuerySolutionNode* root = soln->root.get();
// Root should be a fetch w/o any filters.
if (STAGE_FETCH != root->getType()) {
return false;
}
if (NULL != root->filter.get()) {
return false;
}
// Child should be an ixscan.
if (STAGE_IXSCAN != root->children[0]->getType()) {
return false;
}
IndexScanNode* isn = static_cast<IndexScanNode*>(root->children[0]);
// No filters allowed and side-stepping isSimpleRange for now. TODO: do we ever see
// isSimpleRange here? because we could well use it. I just don't think we ever do see
// it.
if (NULL != isn->filter.get() || isn->bounds.isSimpleRange) {
return false;
}
// Make sure the bounds are OK.
BSONObj startKey;
bool startKeyInclusive;
BSONObj endKey;
bool endKeyInclusive;
if (!IndexBoundsBuilder::isSingleInterval(
isn->bounds, &startKey, &startKeyInclusive, &endKey, &endKeyInclusive)) {
return false;
}
// Make the count node that we replace the fetch + ixscan with.
CountScanNode* csn = new CountScanNode(isn->index);
csn->startKey = startKey;
csn->startKeyInclusive = startKeyInclusive;
csn->endKey = endKey;
csn->endKeyInclusive = endKeyInclusive;
// Takes ownership of 'cn' and deletes the old root.
soln->root.reset(csn);
return true;
}
/**
* Returns true if indices contains an index that can be used with DistinctNode (the "fast distinct
* hack" node, which can be used only if there is an empty query predicate). Sets indexOut to the
* array index of PlannerParams::indices. Look for the index for the fewest fields. Criteria for
* suitable index is that the index cannot be special (geo, hashed, text, ...), and the index cannot
* be a partial index.
*
* Multikey indices are not suitable for DistinctNode when the projection is on an array element.
* Arrays are flattened in a multikey index which makes it impossible for the distinct scan stage
* (plan stage generated from DistinctNode) to select the requested element by array index.
*
* Multikey indices cannot be used for the fast distinct hack if the field is dotted. Currently the
* solution generated for the distinct hack includes a projection stage and the projection stage
* cannot be covered with a dotted field.
*/
bool getDistinctNodeIndex(const std::vector<IndexEntry>& indices,
const std::string& field,
const CollatorInterface* collator,
size_t* indexOut) {
invariant(indexOut);
bool isDottedField = str::contains(field, '.');
int minFields = std::numeric_limits<int>::max();
for (size_t i = 0; i < indices.size(); ++i) {
// Skip indices with non-matching collator.
if (!CollatorInterface::collatorsMatch(indices[i].collator, collator)) {
continue;
}
// Skip special indices.
if (!IndexNames::findPluginName(indices[i].keyPattern).empty()) {
continue;
}
// Skip partial indices.
if (indices[i].filterExpr) {
continue;
}
// Skip multikey indices if we are projecting on a dotted field.
if (indices[i].multikey && isDottedField) {
continue;
}
// Skip indices where the first key is not field.
if (indices[i].keyPattern.firstElement().fieldNameStringData() != StringData(field)) {
continue;
}
int nFields = indices[i].keyPattern.nFields();
// Pick the index with the lowest number of fields.
if (nFields < minFields) {
minFields = nFields;
*indexOut = i;
}
}
return minFields != std::numeric_limits<int>::max();
}
/**
* Checks dotted field for a projection and truncates the
* field name if we could be projecting on an array element.
* Sets 'isIDOut' to true if the projection is on a sub document of _id.
* For example, _id.a.2, _id.b.c.
*/
std::string getProjectedDottedField(const std::string& field, bool* isIDOut) {
// Check if field contains an array index.
std::vector<std::string> res;
mongo::splitStringDelim(field, &res, '.');
// Since we could exit early from the loop,
// we should check _id here and set '*isIDOut' accordingly.
*isIDOut = ("_id" == res[0]);
// Skip the first dotted component. If the field starts
// with a number, the number cannot be an array index.
int arrayIndex = 0;
for (size_t i = 1; i < res.size(); ++i) {
if (mongo::parseNumberFromStringWithBase(res[i], 10, &arrayIndex).isOK()) {
// Array indices cannot be negative numbers (this is not $slice).
// Negative numbers are allowed as field names.
if (arrayIndex >= 0) {
// Generate prefix of field up to (but not including) array index.
std::vector<std::string> prefixStrings(res);
prefixStrings.resize(i);
// Reset projectedField. Instead of overwriting, joinStringDelim() appends joined
// string
// to the end of projectedField.
std::string projectedField;
mongo::joinStringDelim(prefixStrings, &projectedField, '.');
return projectedField;
}
}
}
return field;
}
/**
* Creates a projection spec for a distinct command from the requested field.
* In most cases, the projection spec will be {_id: 0, key: 1}.
* The exceptions are:
* 1) When the requested field is '_id', the projection spec will {_id: 1}.
* 2) When the requested field could be an array element (eg. a.0),
* the projected field will be the prefix of the field up to the array element.
* For example, a.b.2 => {_id: 0, 'a.b': 1}
* Note that we can't use a $slice projection because the distinct command filters
* the results from the executor using the dotted field name. Using $slice will
* re-order the documents in the array in the results.
*/
BSONObj getDistinctProjection(const std::string& field) {
std::string projectedField(field);
bool isID = false;
if ("_id" == field) {
isID = true;
} else if (str::contains(field, '.')) {
projectedField = getProjectedDottedField(field, &isID);
}
BSONObjBuilder bob;
if (!isID) {
bob.append("_id", 0);
}
bob.append(projectedField, 1);
return bob.obj();
}
} // namespace
StatusWith<unique_ptr<PlanExecutor>> getExecutorCount(OperationContext* opCtx,
Collection* collection,
const CountRequest& request,
bool explain,
PlanExecutor::YieldPolicy yieldPolicy) {
unique_ptr<WorkingSet> ws = make_unique<WorkingSet>();
auto qr = stdx::make_unique<QueryRequest>(request.getNs());
qr->setFilter(request.getQuery());
qr->setCollation(request.getCollation());
qr->setHint(request.getHint());
qr->setExplain(explain);
auto statusWithCQ = CanonicalQuery::canonicalize(
opCtx,
std::move(qr),
collection ? static_cast<const ExtensionsCallback&>(
ExtensionsCallbackReal(opCtx, &collection->ns()))
: static_cast<const ExtensionsCallback&>(ExtensionsCallbackNoop()));
if (!statusWithCQ.isOK()) {
return statusWithCQ.getStatus();
}
unique_ptr<CanonicalQuery> cq = std::move(statusWithCQ.getValue());
if (!collection) {
// Treat collections that do not exist as empty collections. Note that the explain
// reporting machinery always assumes that the root stage for a count operation is
// a CountStage, so in this case we put a CountStage on top of an EOFStage.
const bool useRecordStoreCount = false;
CountStageParams params(request, useRecordStoreCount);
unique_ptr<PlanStage> root = make_unique<CountStage>(
opCtx, collection, std::move(params), ws.get(), new EOFStage(opCtx));
return PlanExecutor::make(
opCtx, std::move(ws), std::move(root), request.getNs(), yieldPolicy);
}
// If the query is empty, then we can determine the count by just asking the collection
// for its number of records. This is implemented by the CountStage, and we don't need
// to create a child for the count stage in this case.
//
// If there is a hint, then we can't use a trival count plan as described above.
const bool isEmptyQueryPredicate =
cq->root()->matchType() == MatchExpression::AND && cq->root()->numChildren() == 0;
const bool useRecordStoreCount = isEmptyQueryPredicate && request.getHint().isEmpty();
CountStageParams params(request, useRecordStoreCount);
if (useRecordStoreCount) {
unique_ptr<PlanStage> root =
make_unique<CountStage>(opCtx, collection, std::move(params), ws.get(), nullptr);
return PlanExecutor::make(
opCtx, std::move(ws), std::move(root), request.getNs(), yieldPolicy);
}
const size_t plannerOptions = QueryPlannerParams::IS_COUNT;
StatusWith<PrepareExecutionResult> executionResult =
prepareExecution(opCtx, collection, ws.get(), std::move(cq), plannerOptions);
if (!executionResult.isOK()) {
return executionResult.getStatus();
}
cq = std::move(executionResult.getValue().canonicalQuery);
unique_ptr<QuerySolution> querySolution = std::move(executionResult.getValue().querySolution);
unique_ptr<PlanStage> root = std::move(executionResult.getValue().root);
invariant(root);
// Make a CountStage to be the new root.
root = make_unique<CountStage>(opCtx, collection, std::move(params), ws.get(), root.release());
// We must have a tree of stages in order to have a valid plan executor, but the query
// solution may be NULL. Takes ownership of all args other than 'collection' and 'opCtx'
return PlanExecutor::make(opCtx,
std::move(ws),
std::move(root),
std::move(querySolution),
std::move(cq),
collection,
yieldPolicy);
}
//
// Distinct hack
//
bool turnIxscanIntoDistinctIxscan(QuerySolution* soln, const string& field) {
QuerySolutionNode* root = soln->root.get();
// Root stage must be a project.
if (STAGE_PROJECTION != root->getType()) {
return false;
}
// Child should be either an ixscan or fetch.
if (STAGE_IXSCAN != root->children[0]->getType() &&
STAGE_FETCH != root->children[0]->getType()) {
return false;
}
IndexScanNode* indexScanNode = nullptr;
FetchNode* fetchNode = nullptr;
if (STAGE_IXSCAN == root->children[0]->getType()) {
indexScanNode = static_cast<IndexScanNode*>(root->children[0]);
} else {
fetchNode = static_cast<FetchNode*>(root->children[0]);
// If the fetch has a filter, we're out of luck. We can't skip all keys with a given value,
// since one of them may key a document that passes the filter.
if (fetchNode->filter) {
return false;
}
if (STAGE_IXSCAN != fetchNode->children[0]->getType()) {
return false;
}
indexScanNode = static_cast<IndexScanNode*>(fetchNode->children[0]);
}
// An additional filter must be applied to the data in the key, so we can't just skip
// all the keys with a given value; we must examine every one to find the one that (may)
// pass the filter.
if (indexScanNode->filter) {
return false;
}
// We only set this when we have special query modifiers (.max() or .min()) or other
// special cases. Don't want to handle the interactions between those and distinct.
// Don't think this will ever really be true but if it somehow is, just ignore this
// soln.
if (indexScanNode->bounds.isSimpleRange) {
return false;
}
// Make a new DistinctNode. We will swap this for the ixscan in the provided solution.
auto distinctNode = stdx::make_unique<DistinctNode>(indexScanNode->index);
distinctNode->direction = indexScanNode->direction;
distinctNode->bounds = indexScanNode->bounds;
// Figure out which field we're skipping to the next value of.
distinctNode->fieldNo = 0;
BSONObjIterator it(indexScanNode->index.keyPattern);
while (it.more()) {
if (field == it.next().fieldName()) {
break;
}
distinctNode->fieldNo++;
}
if (fetchNode) {
// If there is a fetch node, then there is no need for the projection. The fetch node should
// become the new root, with the distinct as its child. The PROJECT=>FETCH=>IXSCAN tree
// should become FETCH=>DISTINCT_SCAN.
invariant(STAGE_PROJECTION == root->getType());
invariant(STAGE_FETCH == root->children[0]->getType());
invariant(STAGE_IXSCAN == root->children[0]->children[0]->getType());
// Detach the fetch from its parent projection.
root->children.clear();
// Make the fetch the new root. This destroys the project stage.
soln->root.reset(fetchNode);
// Take ownership of the index scan node, detaching it from the solution tree.
std::unique_ptr<IndexScanNode> ownedIsn(indexScanNode);
// Attach the distinct node in the index scan's place.
fetchNode->children[0] = distinctNode.release();
} else {
// There is no fetch node. The PROJECT=>IXSCAN tree should become PROJECT=>DISTINCT_SCAN.
invariant(STAGE_PROJECTION == root->getType());
invariant(STAGE_IXSCAN == root->children[0]->getType());
// Take ownership of the index scan node, detaching it from the solution tree.
std::unique_ptr<IndexScanNode> ownedIsn(indexScanNode);
// Attach the distinct node in the index scan's place.
root->children[0] = distinctNode.release();
}
return true;
}
StatusWith<unique_ptr<PlanExecutor>> getExecutorDistinct(OperationContext* opCtx,
Collection* collection,
const std::string& ns,
ParsedDistinct* parsedDistinct,
PlanExecutor::YieldPolicy yieldPolicy) {
if (!collection) {
// Treat collections that do not exist as empty collections.
return PlanExecutor::make(opCtx,
make_unique<WorkingSet>(),
make_unique<EOFStage>(opCtx),
parsedDistinct->releaseQuery(),
collection,
yieldPolicy);
}
// TODO: check for idhack here?
// When can we do a fast distinct hack?
// 1. There is a plan with just one leaf and that leaf is an ixscan.
// 2. The ixscan indexes the field we're interested in.
// 2a: We are correct if the index contains the field but for now we look for prefix.
// 3. The query is covered/no fetch.
//
// We go through normal planning (with limited parameters) to see if we can produce
// a soln with the above properties.
QueryPlannerParams plannerParams;
plannerParams.options = QueryPlannerParams::NO_TABLE_SCAN;
IndexCatalog::IndexIterator ii = collection->getIndexCatalog()->getIndexIterator(opCtx, false);
while (ii.more()) {
const IndexDescriptor* desc = ii.next();
IndexCatalogEntry* ice = ii.catalogEntry(desc);
if (desc->keyPattern().hasField(parsedDistinct->getKey())) {
plannerParams.indices.push_back(IndexEntry(desc->keyPattern(),
desc->getAccessMethodName(),
desc->isMultikey(opCtx),
ice->getMultikeyPaths(opCtx),
desc->isSparse(),
desc->unique(),
desc->indexName(),
ice->getFilterExpression(),
desc->infoObj(),
ice->getCollator()));
}
}
const ExtensionsCallbackReal extensionsCallback(opCtx, &collection->ns());
// If there are no suitable indices for the distinct hack bail out now into regular planning
// with no projection.
if (plannerParams.indices.empty()) {
return getExecutor(opCtx, collection, parsedDistinct->releaseQuery(), yieldPolicy);
}
//
// If we're here, we have an index prefixed by the field we're distinct-ing over.
//
// Applying a projection allows the planner to try to give us covered plans that we can turn
// into the projection hack. getDistinctProjection deals with .find() projection semantics
// (ie _id:1 being implied by default).
BSONObj projection = getDistinctProjection(parsedDistinct->getKey());
auto qr = stdx::make_unique<QueryRequest>(parsedDistinct->getQuery()->getQueryRequest());
qr->setProj(projection);
auto statusWithCQ = CanonicalQuery::canonicalize(opCtx, std::move(qr), extensionsCallback);
if (!statusWithCQ.isOK()) {
return statusWithCQ.getStatus();
}
unique_ptr<CanonicalQuery> cq = std::move(statusWithCQ.getValue());
// If the canonical query does not have a user-specified collation, set it from the collection
// default.
if (cq->getQueryRequest().getCollation().isEmpty() && collection->getDefaultCollator()) {
cq->setCollator(collection->getDefaultCollator()->clone());
}
// If there's no query, we can just distinct-scan one of the indices.
// Not every index in plannerParams.indices may be suitable. Refer to
// getDistinctNodeIndex().
size_t distinctNodeIndex = 0;
if (parsedDistinct->getQuery()->getQueryRequest().getFilter().isEmpty() &&
getDistinctNodeIndex(plannerParams.indices,
parsedDistinct->getKey(),
cq->getCollator(),
&distinctNodeIndex)) {
auto dn = stdx::make_unique<DistinctNode>(plannerParams.indices[distinctNodeIndex]);
dn->direction = 1;
IndexBoundsBuilder::allValuesBounds(dn->index.keyPattern, &dn->bounds);
dn->fieldNo = 0;
// An index with a non-simple collation requires a FETCH stage.
std::unique_ptr<QuerySolutionNode> solnRoot = std::move(dn);
if (plannerParams.indices[distinctNodeIndex].collator) {
if (!solnRoot->fetched()) {
auto fetch = stdx::make_unique<FetchNode>();
fetch->children.push_back(solnRoot.release());
solnRoot = std::move(fetch);
}
}
QueryPlannerParams params;
unique_ptr<QuerySolution> soln(
QueryPlannerAnalysis::analyzeDataAccess(*cq, params, solnRoot.release()));
invariant(soln);
unique_ptr<WorkingSet> ws = make_unique<WorkingSet>();
PlanStage* rawRoot;
verify(StageBuilder::build(opCtx, collection, *cq, *soln, ws.get(), &rawRoot));
unique_ptr<PlanStage> root(rawRoot);
LOG(2) << "Using fast distinct: " << redact(cq->toStringShort())
<< ", planSummary: " << redact(Explain::getPlanSummary(root.get()));
return PlanExecutor::make(opCtx,
std::move(ws),
std::move(root),
std::move(soln),
std::move(cq),
collection,
yieldPolicy);
}
// See if we can answer the query in a fast-distinct compatible fashion.
vector<QuerySolution*> solutions;
Status status = QueryPlanner::plan(*cq, plannerParams, &solutions);
if (!status.isOK()) {
return getExecutor(opCtx, collection, std::move(cq), yieldPolicy);
}
// We look for a solution that has an ixscan we can turn into a distinctixscan
for (size_t i = 0; i < solutions.size(); ++i) {
if (turnIxscanIntoDistinctIxscan(solutions[i], parsedDistinct->getKey())) {
// Great, we can use solutions[i]. Clean up the other QuerySolution(s).
for (size_t j = 0; j < solutions.size(); ++j) {
if (j != i) {
delete solutions[j];
}
}
// Build and return the SSR over solutions[i].
unique_ptr<WorkingSet> ws = make_unique<WorkingSet>();
unique_ptr<QuerySolution> currentSolution(solutions[i]);
PlanStage* rawRoot;
verify(
StageBuilder::build(opCtx, collection, *cq, *currentSolution, ws.get(), &rawRoot));
unique_ptr<PlanStage> root(rawRoot);
LOG(2) << "Using fast distinct: " << redact(cq->toStringShort())
<< ", planSummary: " << redact(Explain::getPlanSummary(root.get()));
return PlanExecutor::make(opCtx,
std::move(ws),
std::move(root),
std::move(currentSolution),
std::move(cq),
collection,
yieldPolicy);
}
}
// If we're here, the planner made a soln with the restricted index set but we couldn't
// translate any of them into a distinct-compatible soln. So, delete the solutions and just
// go through normal planning.
for (size_t i = 0; i < solutions.size(); ++i) {
delete solutions[i];
}
return getExecutor(opCtx, collection, parsedDistinct->releaseQuery(), yieldPolicy);
}
} // namespace mongo
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