/
planner_access.cpp
1502 lines (1306 loc) · 63.4 KB
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planner_access.cpp
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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.
*/
#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kQuery
#include "mongo/platform/basic.h"
#include "mongo/db/query/planner_access.h"
#include <algorithm>
#include <memory>
#include <vector>
#include "mongo/base/owned_pointer_vector.h"
#include "mongo/bson/simple_bsonobj_comparator.h"
#include "mongo/db/bson/dotted_path_support.h"
#include "mongo/db/matcher/expression_array.h"
#include "mongo/db/matcher/expression_geo.h"
#include "mongo/db/matcher/expression_text.h"
#include "mongo/db/query/index_bounds_builder.h"
#include "mongo/db/query/index_tag.h"
#include "mongo/db/query/indexability.h"
#include "mongo/db/query/planner_wildcard_helpers.h"
#include "mongo/db/query/query_knobs_gen.h"
#include "mongo/db/query/query_planner.h"
#include "mongo/db/query/query_planner_common.h"
#include "mongo/util/log.h"
#include "mongo/util/transitional_tools_do_not_use/vector_spooling.h"
namespace {
using namespace mongo;
namespace wcp = ::mongo::wildcard_planning;
namespace dps = ::mongo::dotted_path_support;
/**
* Text node functors.
*/
bool isTextNode(const QuerySolutionNode* node) {
return STAGE_TEXT == node->getType();
}
/**
* Casts 'node' to a FetchNode* if it is a FetchNode, otherwise returns null.
*/
FetchNode* getFetchNode(QuerySolutionNode* node) {
if (STAGE_FETCH != node->getType()) {
return nullptr;
}
return static_cast<FetchNode*>(node);
}
/**
* If 'node' is an index scan node, casts it to IndexScanNode*. If 'node' is a FetchNode with an
* IndexScanNode child, then returns a pointer to the child index scan node. Otherwise returns
* null.
*/
const IndexScanNode* getIndexScanNode(const QuerySolutionNode* node) {
if (STAGE_IXSCAN == node->getType()) {
return static_cast<const IndexScanNode*>(node);
} else if (STAGE_FETCH == node->getType()) {
invariant(1U == node->children.size());
const QuerySolutionNode* child = node->children[0];
if (STAGE_IXSCAN == child->getType()) {
return static_cast<const IndexScanNode*>(child);
}
}
return nullptr;
}
/**
* Takes as input two query solution nodes returned by processIndexScans(). If both are
* IndexScanNode or FetchNode with an IndexScanNode child and the index scan nodes are identical
* (same bounds, same filter, same direction, etc.), then returns true. Otherwise returns false.
*/
bool scansAreEquivalent(const QuerySolutionNode* lhs, const QuerySolutionNode* rhs) {
const IndexScanNode* leftIxscan = getIndexScanNode(lhs);
const IndexScanNode* rightIxscan = getIndexScanNode(rhs);
if (!leftIxscan || !rightIxscan) {
return false;
}
return *leftIxscan == *rightIxscan;
}
/**
* If all nodes can provide the requested sort, returns a vector expressing which nodes must have
* their index scans reversed to provide the sort. Otherwise, returns an empty vector.
* 'nodes' must not be empty.
*/
std::vector<bool> canProvideSortWithMergeSort(
const std::vector<std::unique_ptr<QuerySolutionNode>>& nodes, const BSONObj& requestedSort) {
invariant(!nodes.empty());
std::vector<bool> shouldReverseScan;
const auto reverseSort = QueryPlannerCommon::reverseSortObj(requestedSort);
for (auto&& node : nodes) {
node->computeProperties();
auto sorts = node->getSort();
if (sorts.find(requestedSort) != sorts.end()) {
shouldReverseScan.push_back(false);
} else if (sorts.find(reverseSort) != sorts.end()) {
shouldReverseScan.push_back(true);
} else {
return {};
}
}
return shouldReverseScan;
}
} // namespace
namespace mongo {
using std::unique_ptr;
using std::vector;
namespace {
/**
* Extracts the lower and upper bounds on the "ts" field from 'me'. This only examines comparisons
* of "ts" against a Timestamp at the top level or inside a top-level $and.
*/
std::pair<boost::optional<Timestamp>, boost::optional<Timestamp>> extractTsRange(
const MatchExpression* me, bool topLevel = true) {
boost::optional<Timestamp> min;
boost::optional<Timestamp> max;
if (me->matchType() == MatchExpression::AND && topLevel) {
for (size_t i = 0; i < me->numChildren(); ++i) {
boost::optional<Timestamp> childMin;
boost::optional<Timestamp> childMax;
std::tie(childMin, childMax) = extractTsRange(me->getChild(i), false);
if (childMin && (!min || childMin.get() > min.get())) {
min = childMin;
}
if (childMax && (!max || childMax.get() < max.get())) {
max = childMax;
}
}
return {min, max};
}
if (!ComparisonMatchExpression::isComparisonMatchExpression(me) ||
me->path() != repl::OpTime::kTimestampFieldName) {
return {min, max};
}
auto rawElem = static_cast<const ComparisonMatchExpression*>(me)->getData();
if (rawElem.type() != BSONType::bsonTimestamp) {
return {min, max};
}
switch (me->matchType()) {
case MatchExpression::EQ:
min = rawElem.timestamp();
max = rawElem.timestamp();
return {min, max};
case MatchExpression::GT:
case MatchExpression::GTE:
min = rawElem.timestamp();
return {min, max};
case MatchExpression::LT:
case MatchExpression::LTE:
max = rawElem.timestamp();
return {min, max};
default:
MONGO_UNREACHABLE;
}
}
/**
* Returns true if 'me' is a GTE or GE predicate over the "ts" field.
*/
bool isOplogTsLowerBoundPred(const mongo::MatchExpression* me) {
if (mongo::MatchExpression::GT != me->matchType() &&
mongo::MatchExpression::GTE != me->matchType()) {
return false;
}
return me->path() == repl::OpTime::kTimestampFieldName;
}
} // namespace
std::unique_ptr<QuerySolutionNode> QueryPlannerAccess::makeCollectionScan(
const CanonicalQuery& query, bool tailable, const QueryPlannerParams& params) {
// Make the (only) node, a collection scan.
auto csn = std::make_unique<CollectionScanNode>();
csn->name = query.ns();
csn->filter = query.root()->shallowClone();
csn->tailable = tailable;
csn->shouldTrackLatestOplogTimestamp =
params.options & QueryPlannerParams::TRACK_LATEST_OPLOG_TS;
csn->shouldWaitForOplogVisibility =
params.options & QueryPlannerParams::OPLOG_SCAN_WAIT_FOR_VISIBLE;
// If the hint is {$natural: +-1} this changes the direction of the collection scan.
if (!query.getQueryRequest().getHint().isEmpty()) {
BSONElement natural =
dps::extractElementAtPath(query.getQueryRequest().getHint(), "$natural");
if (!natural.eoo()) {
csn->direction = natural.numberInt() >= 0 ? 1 : -1;
}
}
// The sort can specify $natural as well. The sort direction should override the hint
// direction if both are specified.
const BSONObj& sortObj = query.getQueryRequest().getSort();
if (!sortObj.isEmpty()) {
BSONElement natural = dps::extractElementAtPath(sortObj, "$natural");
if (!natural.eoo()) {
csn->direction = natural.numberInt() >= 0 ? 1 : -1;
}
}
if (query.nss().isOplog() && csn->direction == 1) {
// Optimizes the start and end location parameters for a collection scan for an oplog
// collection.
std::tie(csn->minTs, csn->maxTs) = extractTsRange(query.root());
// If the query is just a lower bound on "ts" on a forward scan, 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 (isOplogTsLowerBoundPred(query.root())) {
csn->stopApplyingFilterAfterFirstMatch = true;
}
}
return std::move(csn);
}
std::unique_ptr<QuerySolutionNode> QueryPlannerAccess::makeLeafNode(
const CanonicalQuery& query,
const IndexEntry& index,
size_t pos,
const MatchExpression* expr,
IndexBoundsBuilder::BoundsTightness* tightnessOut) {
// We're guaranteed that all GEO_NEARs are first. This slightly violates the "sort index
// predicates by their position in the compound index" rule but GEO_NEAR isn't an ixscan.
// This saves our bacon when we have {foo: 1, bar: "2dsphere"} and the predicate on bar is a
// $near. If we didn't get the GEO_NEAR first we'd create an IndexScanNode and later cast
// it to a GeoNear2DSphereNode
//
// This should gracefully deal with the case where we have a pred over foo but no geo clause
// over bar. In that case there is no GEO_NEAR to appear first and it's treated like a
// straight ixscan.
if (MatchExpression::GEO_NEAR == expr->matchType()) {
// We must not keep the expression node around.
*tightnessOut = IndexBoundsBuilder::EXACT;
auto nearExpr = static_cast<const GeoNearMatchExpression*>(expr);
BSONElement elt = index.keyPattern.firstElement();
bool indexIs2D = (String == elt.type() && "2d" == elt.String());
if (indexIs2D) {
auto ret = std::make_unique<GeoNear2DNode>(index);
ret->nq = &nearExpr->getData();
ret->baseBounds.fields.resize(index.keyPattern.nFields());
if (nullptr != query.getProj()) {
ret->addPointMeta = query.getProj()->wantGeoNearPoint();
ret->addDistMeta = query.getProj()->wantGeoNearDistance();
}
return std::move(ret);
} else {
auto ret = std::make_unique<GeoNear2DSphereNode>(index);
ret->nq = &nearExpr->getData();
ret->baseBounds.fields.resize(index.keyPattern.nFields());
if (nullptr != query.getProj()) {
ret->addPointMeta = query.getProj()->wantGeoNearPoint();
ret->addDistMeta = query.getProj()->wantGeoNearDistance();
}
return std::move(ret);
}
} else if (MatchExpression::TEXT == expr->matchType()) {
// We must not keep the expression node around.
*tightnessOut = IndexBoundsBuilder::EXACT;
auto textExpr = static_cast<const TextMatchExpressionBase*>(expr);
auto ret = std::make_unique<TextNode>(index);
ret->ftsQuery = textExpr->getFTSQuery().clone();
// Count the number of prefix fields before the "text" field.
for (auto&& keyPatternElt : ret->index.keyPattern) {
// We know that the only key pattern with a type of String is the _fts field
// which is immediately after all prefix fields.
if (BSONType::String == keyPatternElt.type()) {
break;
}
++(ret->numPrefixFields);
}
return std::move(ret);
} else {
// Note that indexKeyPattern.firstElement().fieldName() may not equal expr->path()
// because expr might be inside an array operator that provides a path prefix.
auto isn = std::make_unique<IndexScanNode>(index);
isn->bounds.fields.resize(index.keyPattern.nFields());
isn->addKeyMetadata = query.getQueryRequest().returnKey();
isn->queryCollator = query.getCollator();
// Get the ixtag->pos-th element of the index key pattern.
// TODO: cache this instead/with ixtag->pos?
BSONObjIterator it(index.keyPattern);
BSONElement keyElt = it.next();
for (size_t i = 0; i < pos; ++i) {
verify(it.more());
keyElt = it.next();
}
verify(!keyElt.eoo());
IndexBoundsBuilder::translate(expr, keyElt, index, &isn->bounds.fields[pos], tightnessOut);
return std::move(isn);
}
}
bool QueryPlannerAccess::shouldMergeWithLeaf(const MatchExpression* expr,
const ScanBuildingState& scanState) {
const QuerySolutionNode* node = scanState.currentScan.get();
if (nullptr == node || nullptr == expr) {
return false;
}
if (nullptr == scanState.ixtag) {
return false;
}
if (scanState.currentIndexNumber != scanState.ixtag->index) {
return false;
}
size_t pos = scanState.ixtag->pos;
const IndexEntry& index = scanState.indices[scanState.currentIndexNumber];
const MatchExpression::MatchType mergeType = scanState.root->matchType();
const StageType type = node->getType();
const MatchExpression::MatchType exprType = expr->matchType();
//
// First handle special solution tree leaf types. In general, normal index bounds
// building is not used for special leaf types, and hence we cannot merge leaves.
//
// This rule is always true for OR, but there are exceptions for AND.
// Specifically, we can often merge a predicate with a special leaf type
// by adding a filter to the special leaf type.
//
if (STAGE_TEXT == type) {
// Currently only one text predicate is allowed, but to be safe, make sure that we
// do not try to merge two text predicates.
return MatchExpression::AND == mergeType && MatchExpression::TEXT != exprType;
}
if (STAGE_GEO_NEAR_2D == type || STAGE_GEO_NEAR_2DSPHERE == type) {
// Currently only one GEO_NEAR is allowed, but to be safe, make sure that we
// do not try to merge two GEO_NEAR predicates.
return MatchExpression::AND == mergeType && MatchExpression::GEO_NEAR != exprType;
}
//
// If we're here, then we're done checking for special leaf nodes, and the leaf
// must be a regular index scan.
//
invariant(type == STAGE_IXSCAN);
const IndexScanNode* scan = static_cast<const IndexScanNode*>(node);
const IndexBounds* boundsToFillOut = &scan->bounds;
if (boundsToFillOut->fields[pos].name.empty()) {
// Bounds have yet to be assigned for the 'pos' position in the index. The plan enumerator
// should have told us that it is safe to compound bounds in this case.
invariant(scanState.ixtag->canCombineBounds);
return true;
} else {
// Bounds have already been assigned for the 'pos' position in the index.
if (MatchExpression::AND == mergeType) {
// The bounds on the 'pos' position in the index would be intersected if we merged these
// two leaf expressions.
if (!scanState.ixtag->canCombineBounds) {
// If the plan enumerator told us that it isn't safe to intersect bounds in this
// case, then it must be because we're using a multikey index.
invariant(index.multikey);
}
return scanState.ixtag->canCombineBounds;
} else {
// The bounds will be unionized.
return true;
}
}
}
void QueryPlannerAccess::mergeWithLeafNode(MatchExpression* expr, ScanBuildingState* scanState) {
QuerySolutionNode* node = scanState->currentScan.get();
invariant(nullptr != node);
const MatchExpression::MatchType mergeType = scanState->root->matchType();
size_t pos = scanState->ixtag->pos;
const IndexEntry& index = scanState->indices[scanState->currentIndexNumber];
const StageType type = node->getType();
if (STAGE_TEXT == type) {
auto textNode = static_cast<TextNode*>(node);
if (pos < textNode->numPrefixFields) {
// This predicate is assigned to one of the prefix fields of the text index. Such
// predicates must always be equalities and must always be attached to the TEXT node. In
// order to ensure this happens, we assign INEXACT_COVERED tightness.
scanState->tightness = IndexBoundsBuilder::INEXACT_COVERED;
} else {
// The predicate is assigned to one of the trailing fields of the text index. We
// currently don't generate bounds for predicates assigned to trailing fields of a text
// index, but rather attempt to attach a covered filter. However, certain predicates can
// never be correctly covered (e.g. $exists), so we assign the tightness accordingly.
scanState->tightness = IndexBoundsBuilder::canUseCoveredMatching(expr, index)
? IndexBoundsBuilder::INEXACT_COVERED
: IndexBoundsBuilder::INEXACT_FETCH;
}
return;
}
IndexBounds* boundsToFillOut = nullptr;
if (STAGE_GEO_NEAR_2D == type) {
invariant(INDEX_2D == index.type);
// 2D indexes have a special format - the "2d" field stores a normally-indexed BinData
// field, but additional array fields are *not* exploded into multi-keys - they are stored
// directly as arrays in the index. Also, no matter what the index expression, the "2d"
// field is always first.
//
// This means that we can only generically accumulate bounds for 2D indexes over the first
// "2d" field (pos == 0) - MatchExpressions over other fields in the 2D index may be covered
// (can be evaluated using only the 2D index key). The additional fields must not affect
// the index scan bounds, since they are not stored in an IndexScan-compatible format.
if (pos > 0) {
// The predicate is over a trailing field of the "2d" index. If possible, we assign it
// as a covered filter (the INEXACT_COVERED case). Otherwise, the filter must be
// evaluated after fetching the full documents.
scanState->tightness = IndexBoundsBuilder::canUseCoveredMatching(expr, index)
? IndexBoundsBuilder::INEXACT_COVERED
: IndexBoundsBuilder::INEXACT_FETCH;
return;
}
// We may have other $geoPredicates on a near index - generate bounds for these
GeoNear2DNode* gn = static_cast<GeoNear2DNode*>(node);
boundsToFillOut = &gn->baseBounds;
} else if (STAGE_GEO_NEAR_2DSPHERE == type) {
GeoNear2DSphereNode* gn = static_cast<GeoNear2DSphereNode*>(node);
boundsToFillOut = &gn->baseBounds;
} else {
verify(type == STAGE_IXSCAN);
IndexScanNode* scan = static_cast<IndexScanNode*>(node);
// See STAGE_GEO_NEAR_2D above - 2D indexes can only accumulate scan bounds over the first
// "2d" field (pos == 0).
if (INDEX_2D == index.type && pos > 0) {
// The predicate is over a trailing field of the "2d" index. If possible, we assign it
// as a covered filter (the INEXACT_COVERED case). Otherwise, the filter must be
// evaluated after fetching the full documents.
scanState->tightness = IndexBoundsBuilder::canUseCoveredMatching(expr, index)
? IndexBoundsBuilder::INEXACT_COVERED
: IndexBoundsBuilder::INEXACT_FETCH;
return;
}
boundsToFillOut = &scan->bounds;
}
// Get the ixtag->pos-th element of the index key pattern.
// TODO: cache this instead/with ixtag->pos?
BSONObjIterator it(index.keyPattern);
BSONElement keyElt = it.next();
for (size_t i = 0; i < pos; ++i) {
verify(it.more());
keyElt = it.next();
}
verify(!keyElt.eoo());
scanState->tightness = IndexBoundsBuilder::INEXACT_FETCH;
verify(boundsToFillOut->fields.size() > pos);
OrderedIntervalList* oil = &boundsToFillOut->fields[pos];
if (boundsToFillOut->fields[pos].name.empty()) {
IndexBoundsBuilder::translate(expr, keyElt, index, oil, &scanState->tightness);
} else {
if (MatchExpression::AND == mergeType) {
IndexBoundsBuilder::translateAndIntersect(
expr, keyElt, index, oil, &scanState->tightness);
} else {
verify(MatchExpression::OR == mergeType);
IndexBoundsBuilder::translateAndUnion(expr, keyElt, index, oil, &scanState->tightness);
}
}
}
void QueryPlannerAccess::finishTextNode(QuerySolutionNode* node, const IndexEntry& index) {
TextNode* tn = static_cast<TextNode*>(node);
// If there's no prefix, the filter is already on the node and the index prefix is null.
// We can just return.
if (!tn->numPrefixFields) {
return;
}
// We can't create a text stage if there aren't EQ predicates on its prefix terms. So
// if we've made it this far, we should have collected the prefix predicates in the
// filter.
invariant(nullptr != tn->filter.get());
MatchExpression* textFilterMe = tn->filter.get();
BSONObjBuilder prefixBob;
if (MatchExpression::AND != textFilterMe->matchType()) {
// Only one prefix term.
invariant(1u == tn->numPrefixFields);
// Sanity check: must be an EQ.
invariant(MatchExpression::EQ == textFilterMe->matchType());
EqualityMatchExpression* eqExpr = static_cast<EqualityMatchExpression*>(textFilterMe);
prefixBob.append(eqExpr->getData());
tn->filter.reset();
} else {
invariant(MatchExpression::AND == textFilterMe->matchType());
// Indexed by the keyPattern position index assignment. We want to add
// prefixes in order but we must order them first.
vector<MatchExpression*> prefixExprs(tn->numPrefixFields, nullptr);
AndMatchExpression* amExpr = static_cast<AndMatchExpression*>(textFilterMe);
invariant(amExpr->numChildren() >= tn->numPrefixFields);
// Look through the AND children. The prefix children we want to
// stash in prefixExprs.
size_t curChild = 0;
while (curChild < amExpr->numChildren()) {
MatchExpression* child = amExpr->getChild(curChild);
IndexTag* ixtag = static_cast<IndexTag*>(child->getTag());
invariant(nullptr != ixtag);
// Skip this child if it's not part of a prefix, or if we've already assigned a
// predicate to this prefix position.
if (ixtag->pos >= tn->numPrefixFields || prefixExprs[ixtag->pos] != nullptr) {
++curChild;
continue;
}
// prefixExprs takes ownership of 'child'.
prefixExprs[ixtag->pos] = child;
amExpr->getChildVector()->erase(amExpr->getChildVector()->begin() + curChild);
// Don't increment curChild.
}
// Go through the prefix equalities in order and create an index prefix out of them.
for (size_t i = 0; i < prefixExprs.size(); ++i) {
MatchExpression* prefixMe = prefixExprs[i];
invariant(nullptr != prefixMe);
invariant(MatchExpression::EQ == prefixMe->matchType());
EqualityMatchExpression* eqExpr = static_cast<EqualityMatchExpression*>(prefixMe);
prefixBob.append(eqExpr->getData());
// We removed this from the AND expression that owned it, so we must clean it
// up ourselves.
delete prefixMe;
}
// Clear out an empty $and.
if (0 == amExpr->numChildren()) {
tn->filter.reset();
} else if (1 == amExpr->numChildren()) {
// Clear out unsightly only child of $and
MatchExpression* child = amExpr->getChild(0);
amExpr->getChildVector()->clear();
// Deletes current filter which is amExpr.
tn->filter.reset(child);
}
}
tn->indexPrefix = prefixBob.obj();
}
bool QueryPlannerAccess::orNeedsFetch(const ScanBuildingState* scanState) {
if (scanState->loosestBounds == IndexBoundsBuilder::EXACT) {
return false;
} else if (scanState->loosestBounds == IndexBoundsBuilder::INEXACT_FETCH) {
return true;
} else {
invariant(scanState->loosestBounds == IndexBoundsBuilder::INEXACT_COVERED);
const IndexEntry& index = scanState->indices[scanState->currentIndexNumber];
return index.multikey;
}
}
void QueryPlannerAccess::finishAndOutputLeaf(ScanBuildingState* scanState,
vector<std::unique_ptr<QuerySolutionNode>>* out) {
finishLeafNode(scanState->currentScan.get(), scanState->indices[scanState->currentIndexNumber]);
if (MatchExpression::OR == scanState->root->matchType()) {
if (orNeedsFetch(scanState)) {
// In order to correctly evaluate the predicates for this index, we have to
// fetch the full documents. Add a fetch node above the index scan whose filter
// includes *all* of the predicates used to generate the ixscan.
auto fetch = std::make_unique<FetchNode>();
// Takes ownership.
fetch->filter = std::move(scanState->curOr);
// Takes ownership.
fetch->children.push_back(scanState->currentScan.release());
scanState->currentScan = std::move(fetch);
} else if (scanState->loosestBounds == IndexBoundsBuilder::INEXACT_COVERED) {
// This an OR, at least one of the predicates used to generate 'currentScan'
// is inexact covered, but none is inexact fetch. This means that we can put
// these predicates, joined by an $or, as filters on the index scan. This avoids
// a fetch and allows the predicates to be covered by the index.
//
// Ex.
// Say we have index {a: 1} and query {$or: [{a: /foo/}, {a: /bar/}]}.
// The entire query, {$or: [{a: /foo/}, {a: /bar/}]}, should be a filter
// in the index scan stage itself.
scanState->currentScan->filter = std::move(scanState->curOr);
}
}
out->push_back(std::move(scanState->currentScan));
}
void QueryPlannerAccess::finishLeafNode(QuerySolutionNode* node, const IndexEntry& index) {
const StageType type = node->getType();
if (STAGE_TEXT == type) {
return finishTextNode(node, index);
}
IndexEntry* nodeIndex = nullptr;
IndexBounds* bounds = nullptr;
if (STAGE_GEO_NEAR_2D == type) {
GeoNear2DNode* gnode = static_cast<GeoNear2DNode*>(node);
bounds = &gnode->baseBounds;
nodeIndex = &gnode->index;
} else if (STAGE_GEO_NEAR_2DSPHERE == type) {
GeoNear2DSphereNode* gnode = static_cast<GeoNear2DSphereNode*>(node);
bounds = &gnode->baseBounds;
nodeIndex = &gnode->index;
} else {
verify(type == STAGE_IXSCAN);
IndexScanNode* scan = static_cast<IndexScanNode*>(node);
nodeIndex = &scan->index;
bounds = &scan->bounds;
// If this is a $** index, update and populate the keyPattern, bounds, and multikeyPaths.
if (index.type == IndexType::INDEX_WILDCARD) {
wcp::finalizeWildcardIndexScanConfiguration(scan);
}
}
// Find the first field in the scan's bounds that was not filled out.
// TODO: could cache this.
size_t firstEmptyField = 0;
for (firstEmptyField = 0; firstEmptyField < bounds->fields.size(); ++firstEmptyField) {
if (bounds->fields[firstEmptyField].name.empty()) {
verify(bounds->fields[firstEmptyField].intervals.empty());
break;
}
}
// All fields are filled out with bounds, nothing to do.
if (firstEmptyField == bounds->fields.size()) {
return IndexBoundsBuilder::alignBounds(bounds, nodeIndex->keyPattern);
}
// Skip ahead to the firstEmptyField-th element, where we begin filling in bounds.
BSONObjIterator it(nodeIndex->keyPattern);
for (size_t i = 0; i < firstEmptyField; ++i) {
verify(it.more());
it.next();
}
// For each field in the key...
while (it.more()) {
BSONElement kpElt = it.next();
// There may be filled-in fields to the right of the firstEmptyField; for instance, the
// index {loc:"2dsphere", x:1} with a predicate over x and a near search over loc.
if (bounds->fields[firstEmptyField].name.empty()) {
verify(bounds->fields[firstEmptyField].intervals.empty());
IndexBoundsBuilder::allValuesForField(kpElt, &bounds->fields[firstEmptyField]);
}
++firstEmptyField;
}
// Make sure that the length of the key is the length of the bounds we started.
verify(firstEmptyField == bounds->fields.size());
// We create bounds assuming a forward direction but can easily reverse bounds to align
// according to our desired direction.
IndexBoundsBuilder::alignBounds(bounds, nodeIndex->keyPattern);
}
void QueryPlannerAccess::findElemMatchChildren(const MatchExpression* node,
vector<MatchExpression*>* out,
vector<MatchExpression*>* subnodesOut) {
for (size_t i = 0; i < node->numChildren(); ++i) {
MatchExpression* child = node->getChild(i);
if (Indexability::isBoundsGenerating(child) && nullptr != child->getTag()) {
out->push_back(child);
} else if (MatchExpression::AND == child->matchType() ||
Indexability::arrayUsesIndexOnChildren(child)) {
findElemMatchChildren(child, out, subnodesOut);
} else if (nullptr != child->getTag()) {
subnodesOut->push_back(child);
}
}
}
std::vector<std::unique_ptr<QuerySolutionNode>> QueryPlannerAccess::collapseEquivalentScans(
std::vector<std::unique_ptr<QuerySolutionNode>> scans) {
invariant(scans.size() > 0);
// Scans that need to be collapsed will be adjacent to each other in the list due to how we
// sort the query predicate. We step through the list, either merging the current scan into
// the last scan in 'collapsedScans', or adding a new entry to 'collapsedScans' if it can't
// be merged.
std::vector<std::unique_ptr<QuerySolutionNode>> collapsedScans;
collapsedScans.push_back(std::move(scans[0]));
for (size_t i = 1; i < scans.size(); ++i) {
if (scansAreEquivalent(collapsedScans.back().get(), scans[i].get())) {
// We collapse the entry from 'ownedScans' into the back of 'collapsedScans'.
std::unique_ptr<QuerySolutionNode> collapseFrom = std::move(scans[i]);
FetchNode* collapseFromFetch = getFetchNode(collapseFrom.get());
FetchNode* collapseIntoFetch = getFetchNode(collapsedScans.back().get());
// If there's no filter associated with a fetch node on 'collapseFrom', all we have to
// do is clear the filter on the node that we are collapsing into.
if (!collapseFromFetch || !collapseFromFetch->filter.get()) {
if (collapseIntoFetch) {
collapseIntoFetch->filter.reset();
}
continue;
}
// If there's no filter associated with a fetch node on the back of the 'collapsedScans'
// list, then there's nothing more to do.
if (!collapseIntoFetch || !collapseIntoFetch->filter.get()) {
continue;
}
// Both the 'from' and 'into' nodes have filters. We join them with an
// OrMatchExpression.
std::unique_ptr<OrMatchExpression> collapsedFilter =
std::make_unique<OrMatchExpression>();
collapsedFilter->add(collapseFromFetch->filter.release());
collapsedFilter->add(collapseIntoFetch->filter.release());
// Normalize the filter and add it to 'into'.
collapseIntoFetch->filter = MatchExpression::optimize(std::move(collapsedFilter));
} else {
// Scans are not equivalent and can't be collapsed.
collapsedScans.push_back(std::move(scans[i]));
}
}
invariant(collapsedScans.size() > 0);
return collapsedScans;
}
bool QueryPlannerAccess::processIndexScans(const CanonicalQuery& query,
MatchExpression* root,
bool inArrayOperator,
const std::vector<IndexEntry>& indices,
const QueryPlannerParams& params,
std::vector<std::unique_ptr<QuerySolutionNode>>* out) {
// Initialize the ScanBuildingState.
ScanBuildingState scanState(root, inArrayOperator, indices);
while (scanState.curChild < root->numChildren()) {
MatchExpression* child = root->getChild(scanState.curChild);
// If there is no tag, it's not using an index. We've sorted our children such that the
// children with tags are first, so we stop now.
if (nullptr == child->getTag()) {
break;
}
scanState.ixtag = static_cast<IndexTag*>(child->getTag());
// If there's a tag it must be valid.
verify(IndexTag::kNoIndex != scanState.ixtag->index);
// If the child can't use an index on its own field (and the child is not a negation
// of a bounds-generating expression), then it's indexed by virtue of one of
// its children having an index.
//
// NOTE: If the child is logical, it could possibly collapse into a single ixscan. we
// ignore this for now.
if (!Indexability::isBoundsGenerating(child)) {
// If we're here, then the child is indexed by virtue of its children.
// In most cases this means that we recursively build indexed data
// access on 'child'.
if (!processIndexScansSubnode(query, &scanState, params, out)) {
return false;
}
continue;
}
// If we're here, we now know that 'child' can use an index directly and the index is
// over the child's field.
// If 'child' is a NOT, then the tag we're interested in is on the NOT's
// child node.
if (MatchExpression::NOT == child->matchType()) {
scanState.ixtag = static_cast<IndexTag*>(child->getChild(0)->getTag());
invariant(IndexTag::kNoIndex != scanState.ixtag->index);
}
// If the child we're looking at uses a different index than the current index scan, add
// the current index scan to the output as we're done with it. The index scan created
// by the child then becomes our new current index scan. Note that the current scan
// could be NULL, in which case we don't output it. The rest of the logic is identical.
//
// If the child uses the same index as the current index scan, we may be able to merge
// the bounds for the two scans.
//
// Guiding principle: must the values we're testing come from the same array in the
// document? If so, we can combine bounds (via intersection or compounding). If not,
// we can't.
//
// If the index is NOT multikey, it's always semantically correct to combine bounds,
// as there are no arrays to worry about.
//
// If the index is multikey, there are arrays of values. There are several
// complications in the multikey case that have to be obeyed both by the enumerator
// and here as we try to merge predicates into query solution leaves. The hairy
// details of these rules are documented near the top of planner_access.h.
if (shouldMergeWithLeaf(child, scanState)) {
// The child uses the same index we're currently building a scan for. Merge
// the bounds and filters.
verify(scanState.currentIndexNumber == scanState.ixtag->index);
scanState.tightness = IndexBoundsBuilder::INEXACT_FETCH;
mergeWithLeafNode(child, &scanState);
handleFilter(&scanState);
} else {
if (nullptr != scanState.currentScan.get()) {
// Output the current scan before starting to construct a new out.
finishAndOutputLeaf(&scanState, out);
} else {
verify(IndexTag::kNoIndex == scanState.currentIndexNumber);
}
// Reset state before producing a new leaf.
scanState.resetForNextScan(scanState.ixtag);
scanState.currentScan = makeLeafNode(query,
indices[scanState.currentIndexNumber],
scanState.ixtag->pos,
child,
&scanState.tightness);
handleFilter(&scanState);
}
}
// Output the scan we're done with, if it exists.
if (nullptr != scanState.currentScan.get()) {
finishAndOutputLeaf(&scanState, out);
}
return true;
}
bool QueryPlannerAccess::processIndexScansElemMatch(
const CanonicalQuery& query,
ScanBuildingState* scanState,
const QueryPlannerParams& params,
std::vector<std::unique_ptr<QuerySolutionNode>>* out) {
MatchExpression* root = scanState->root;
MatchExpression* child = root->getChild(scanState->curChild);
const vector<IndexEntry>& indices = scanState->indices;
// We have an AND with an ELEM_MATCH_OBJECT child. The plan enumerator produces
// index taggings which indicate that we should try to compound with
// predicates retrieved from inside the subtree rooted at the ELEM_MATCH.
// In order to obey the enumerator's tagging, we need to retrieve these
// predicates from inside the $elemMatch, and try to merge them with
// the current index scan.
// Contains tagged predicates from inside the tree rooted at 'child'
// which are logically part of the AND.
vector<MatchExpression*> emChildren;
// Contains tagged nodes that are not logically part of the AND and
// cannot use the index directly (e.g. OR nodes which are tagged to
// be indexed).
vector<MatchExpression*> emSubnodes;
// Populate 'emChildren' and 'emSubnodes'.
findElemMatchChildren(child, &emChildren, &emSubnodes);
// Recursively build data access for the nodes inside 'emSubnodes'.
for (size_t i = 0; i < emSubnodes.size(); ++i) {
MatchExpression* subnode = emSubnodes[i];
if (!Indexability::isBoundsGenerating(subnode)) {
// 'subnode' is beneath an $elemMatch. When planning the children of array operators, we
// keep ownership of the match expression node. Therefore, we pass nullptr for the
// 'ownedRoot' argument.
auto childSolution = _buildIndexedDataAccess(query, subnode, nullptr, indices, params);
// _buildIndexedDataAccess(...) returns NULL in error conditions, when it is unable to
// construct a query solution from a tagged match expression tree. If we are unable to
// construct a solution according to the instructions from the enumerator, then we bail
// out early (by returning false) rather than continuing on and potentially constructing
// an invalid solution tree.
if (!childSolution) {
return false;
}
// Output the resulting solution tree.
out->push_back(std::move(childSolution));
}
}
// For each predicate in 'emChildren', try to merge it with the current index scan.
//
// This loop is similar to that in processIndexScans(...), except it does not call into
// handleFilters(...). Instead, we leave the entire $elemMatch filter intact. This way,
// the complete $elemMatch expression will be affixed as a filter later on.
for (size_t i = 0; i < emChildren.size(); ++i) {
MatchExpression* emChild = emChildren[i];
invariant(nullptr != emChild->getTag());
scanState->ixtag = static_cast<IndexTag*>(emChild->getTag());
// If 'emChild' is a NOT, then the tag we're interested in is on the NOT's
// child node.
if (MatchExpression::NOT == emChild->matchType()) {
invariant(nullptr != emChild->getChild(0)->getTag());
scanState->ixtag = static_cast<IndexTag*>(emChild->getChild(0)->getTag());
invariant(IndexTag::kNoIndex != scanState->ixtag->index);
}
if (shouldMergeWithLeaf(emChild, *scanState)) {
// The child uses the same index we're currently building a scan for. Merge
// the bounds and filters.
verify(scanState->currentIndexNumber == scanState->ixtag->index);
scanState->tightness = IndexBoundsBuilder::INEXACT_FETCH;
mergeWithLeafNode(emChild, scanState);
} else {
if (nullptr != scanState->currentScan.get()) {
finishAndOutputLeaf(scanState, out);
} else {
verify(IndexTag::kNoIndex == scanState->currentIndexNumber);
}
scanState->currentIndexNumber = scanState->ixtag->index;
scanState->tightness = IndexBoundsBuilder::INEXACT_FETCH;
scanState->currentScan = makeLeafNode(query,
indices[scanState->currentIndexNumber],
scanState->ixtag->pos,
emChild,
&scanState->tightness);
}
}
// We're done processing the $elemMatch child. We leave it hanging off
// it's AND parent so that it will be affixed as a filter later on,
// and move on to the next child of the AND.
++scanState->curChild;
return true;
}