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Diffstat (limited to 'src/mongo/db/query/lite_projection.h')
| -rw-r--r-- | src/mongo/db/query/lite_projection.h | 188 |
1 files changed, 188 insertions, 0 deletions
diff --git a/src/mongo/db/query/lite_projection.h b/src/mongo/db/query/lite_projection.h new file mode 100644 index 00000000000..7958b55c85a --- /dev/null +++ b/src/mongo/db/query/lite_projection.h @@ -0,0 +1,188 @@ +/** + * Copyright (C) 2013 10gen Inc. + * + * This program is free software: you can redistribute it and/or modify + * it under the terms of the GNU Affero General Public License, version 3, + * as published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * 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. + */ + +#pragma once + +#include "mongo/db/jsobj.h" +#include "mongo/db/matcher/expression.h" +#include "mongo/util/string_map.h" + +namespace mongo { + + class LiteProjection { + public: + typedef StringMap<LiteProjection*> FieldMap; + typedef StringMap<MatchExpression*> Matchers; + + enum ArrayOpType { + ARRAY_OP_NORMAL = 0, + ARRAY_OP_ELEM_MATCH, + ARRAY_OP_POSITIONAL + }; + + /** + * Use this to create a LiteProjection. + * + * 'query' is the user's query, used to ensure that the query is consistent with any + * positional operators in the projection. + * + * 'projObj' is the projection. + * + * If 'projObj' is valid (with respect to 'query'), returns Status::OK() and populates *out. + * Caller owns the pointer. + * + * Otherwise, returns an error. + */ + static Status make(const BSONObj& query, const BSONObj& projObj, LiteProjection** out); + + ~LiteProjection(); + + /** + * Is the full document required to compute this projection? + */ + bool requiresDocument() const { + return _include || _hasNonSimple || _hasDottedField; + } + + /** + * Return the fields required to compute the projection in 'fields'. + * + * Assumes that requiresDocument() is false and may produce bogus results if + * requiresDocument() is true. + */ + void getRequiredFields(vector<string>* fields) const; + + /** + * Apply the projection that 'this' represents to the object 'in'. 'details' is the result + * of a match evaluation of the full query on the object 'in'. This is only required + * if the projection is positional. + * + * If the projection is successfully computed, returns Status::OK() and populates 'out'. + * Otherwise, returns error. + */ + Status transform(const BSONObj& in, BSONObj* out, const MatchDetails* details = NULL) const; + + /** + * See transform(...) above. + */ + bool transformRequiresDetails() const { + return ARRAY_OP_POSITIONAL == _arrayOpType; + } + + /** + * Used for debugging. + */ + const BSONObj& getProjectionSpec() const { return _source; } + + private: + friend class ProjectionStage; + + // + // Initialization + // + + /** + * We keep this private so that one must call ::make to create a new instance. + */ + LiteProjection(); + + /** + * Initialize the projection from the provided BSONObj. + * Returns Status::OK() if the provided projection spec is valid. + * Otherwise, returns an error. + */ + Status init(const BSONObj& spec, const BSONObj& query); + + /** + * Add 'field' to the set of things to be projected. + * 'include' specifies whether or not 'field' is to be included or dropped. + * 'skip' and 'limit' are for $slice. + */ + void add(const string& field, bool include); + void add(const string& field, int skip, int limit); + + // + // Execution + // TODO: Move into exec/projection.cpp or elsewhere. + // + + /** + * See transform(...) above. + */ + Status transform(const BSONObj& in, + BSONObjBuilder* bob, + const MatchDetails* details = NULL) const; + + /** + * Appends the element 'e' to the builder 'bob', possibly descending into sub-fields of 'e' + * if needed. + */ + Status append(BSONObjBuilder* bob, + const BSONElement& elt, + const MatchDetails* details = NULL, + const ArrayOpType arrayOpType = ARRAY_OP_NORMAL) const; + + // XXX document + void appendArray(BSONObjBuilder* bob, const BSONObj& array, bool nested = false) const; + + // True if default at this level is to include. + bool _include; + + // True if this level can't be skipped or included without recursing. + bool _special; + + // TODO: benchmark vector<pair> vs map + // XXX: document + FieldMap _fields; + + // The raw projection spec. that is passed into init(...) + BSONObj _source; + + // Should we include the _id field? + bool _includeID; + + // Arguments from the $slice operator. + int _skip; + int _limit; + + // Used for $elemMatch and positional operator ($) + Matchers _matchers; + + // The matchers above point into BSONObjs and this is where those objs live. + vector<BSONObj> _elemMatchObjs; + + ArrayOpType _arrayOpType; + + // Is there an elemMatch or positional operator? + bool _hasNonSimple; + + // Is there a projection over a dotted field? + bool _hasDottedField; + }; + +} // namespace mongo |