diff options
Diffstat (limited to 'src/mongo/db/exec/projection_exec.h')
| -rw-r--r-- | src/mongo/db/exec/projection_exec.h | 316 |
1 files changed, 156 insertions, 160 deletions
diff --git a/src/mongo/db/exec/projection_exec.h b/src/mongo/db/exec/projection_exec.h index 6b8dd1456af..4a1382b4318 100644 --- a/src/mongo/db/exec/projection_exec.h +++ b/src/mongo/db/exec/projection_exec.h @@ -36,166 +36,162 @@ namespace mongo { - class ProjectionExec { - public: - /** - * A .find() projection can have an array operation, either an elemMatch or positional (or - * neither). - */ - enum ArrayOpType { - ARRAY_OP_NORMAL = 0, - ARRAY_OP_ELEM_MATCH, - ARRAY_OP_POSITIONAL - }; - - /** - * Projections based on data computed while answering a query, or other metadata about a - * document / query. - */ - enum MetaProjection { - META_TEXT_SCORE, - META_GEONEAR_DIST, - META_GEONEAR_POINT, - META_RECORDID, - META_IX_KEY, - }; - - /** - * TODO: document why we like StringMap so much here - */ - typedef StringMap<ProjectionExec*> FieldMap; - typedef StringMap<MatchExpression*> Matchers; - typedef StringMap<MetaProjection> MetaMap; - - ProjectionExec(const BSONObj& spec, - const MatchExpression* queryExpression, - const MatchExpressionParser::WhereCallback& whereCallback = - MatchExpressionParser::WhereCallback()); - ~ProjectionExec(); - - /** - * Apply this projection to the 'member'. Changes the type to OWNED_OBJ. - */ - Status transform(WorkingSetMember* member) const; - - /** - * Apply this projection to the object 'in'. - * - * Upon success, 'out' is set to the new object and Status::OK() is returned. - * Otherwise, returns an error Status and *out is not mutated. - */ - Status transform(const BSONObj& in, BSONObj* out) const; - - private: - // - // Initialization - // - - ProjectionExec(); - - /** - * Add 'field' as a field name that is included or excluded as part of the projection. - */ - void add(const std::string& field, bool include); - - /** - * Add 'field' as a field name that is sliced as part of the projection. - */ - void add(const std::string& field, int skip, int limit); - - // - // Execution - // - - /** - * 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 stuff the result in - * 'bob'. - * Otherwise, returns error. - */ - Status transform(const BSONObj& in, - BSONObjBuilder* bob, - const MatchDetails* details = NULL) const; - - /** - * See transform(...) above. - */ - bool transformRequiresDetails() const { - return ARRAY_OP_POSITIONAL == _arrayOpType; - } - - /** - * Is the full document required to compute this projection? - */ - bool requiresDocument() const { - return _include || _hasNonSimple || _hasDottedField; - } - - /** - * 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; - - /** - * Like append, but for arrays. - * Deals with slice and calls appendArray to preserve the array-ness. - */ - 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; - - // We must group projections with common prefixes together. - // TODO: benchmark std::vector<pair> vs map - // - // Projection is a rooted tree. If we have {a.b: 1, a.c: 1} we don't want to - // double-traverse the document when we're projecting it. Instead, we have an entry in - // _fields for 'a' with two sub projections: b:1 and c:1. - 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. - std::vector<BSONObj> _elemMatchObjs; - - ArrayOpType _arrayOpType; - - // Is there an slice, elemMatch or meta operator? - bool _hasNonSimple; - - // Is there a projection over a dotted field or a $ positional operator? - bool _hasDottedField; - - // The full query expression. Used when we need MatchDetails. - const MatchExpression* _queryExpression; - - // Projections that aren't sourced from the document or index keys. - MetaMap _meta; - - // Do we have a returnKey projection? If so we *only* output the index key metadata. If - // it's not found we output nothing. - bool _hasReturnKey; +class ProjectionExec { +public: + /** + * A .find() projection can have an array operation, either an elemMatch or positional (or + * neither). + */ + enum ArrayOpType { ARRAY_OP_NORMAL = 0, ARRAY_OP_ELEM_MATCH, ARRAY_OP_POSITIONAL }; + + /** + * Projections based on data computed while answering a query, or other metadata about a + * document / query. + */ + enum MetaProjection { + META_TEXT_SCORE, + META_GEONEAR_DIST, + META_GEONEAR_POINT, + META_RECORDID, + META_IX_KEY, }; + /** + * TODO: document why we like StringMap so much here + */ + typedef StringMap<ProjectionExec*> FieldMap; + typedef StringMap<MatchExpression*> Matchers; + typedef StringMap<MetaProjection> MetaMap; + + ProjectionExec(const BSONObj& spec, + const MatchExpression* queryExpression, + const MatchExpressionParser::WhereCallback& whereCallback = + MatchExpressionParser::WhereCallback()); + ~ProjectionExec(); + + /** + * Apply this projection to the 'member'. Changes the type to OWNED_OBJ. + */ + Status transform(WorkingSetMember* member) const; + + /** + * Apply this projection to the object 'in'. + * + * Upon success, 'out' is set to the new object and Status::OK() is returned. + * Otherwise, returns an error Status and *out is not mutated. + */ + Status transform(const BSONObj& in, BSONObj* out) const; + +private: + // + // Initialization + // + + ProjectionExec(); + + /** + * Add 'field' as a field name that is included or excluded as part of the projection. + */ + void add(const std::string& field, bool include); + + /** + * Add 'field' as a field name that is sliced as part of the projection. + */ + void add(const std::string& field, int skip, int limit); + + // + // Execution + // + + /** + * 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 stuff the result in + * 'bob'. + * Otherwise, returns error. + */ + Status transform(const BSONObj& in, + BSONObjBuilder* bob, + const MatchDetails* details = NULL) const; + + /** + * See transform(...) above. + */ + bool transformRequiresDetails() const { + return ARRAY_OP_POSITIONAL == _arrayOpType; + } + + /** + * Is the full document required to compute this projection? + */ + bool requiresDocument() const { + return _include || _hasNonSimple || _hasDottedField; + } + + /** + * 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; + + /** + * Like append, but for arrays. + * Deals with slice and calls appendArray to preserve the array-ness. + */ + 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; + + // We must group projections with common prefixes together. + // TODO: benchmark std::vector<pair> vs map + // + // Projection is a rooted tree. If we have {a.b: 1, a.c: 1} we don't want to + // double-traverse the document when we're projecting it. Instead, we have an entry in + // _fields for 'a' with two sub projections: b:1 and c:1. + 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. + std::vector<BSONObj> _elemMatchObjs; + + ArrayOpType _arrayOpType; + + // Is there an slice, elemMatch or meta operator? + bool _hasNonSimple; + + // Is there a projection over a dotted field or a $ positional operator? + bool _hasDottedField; + + // The full query expression. Used when we need MatchDetails. + const MatchExpression* _queryExpression; + + // Projections that aren't sourced from the document or index keys. + MetaMap _meta; + + // Do we have a returnKey projection? If so we *only* output the index key metadata. If + // it's not found we output nothing. + bool _hasReturnKey; +}; + } // namespace mongo |