path: root/src/mongo/db/query/canonical_query.h

/**
 *    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.
 */

#pragma once


#include "mongo/base/status.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/matcher/expression.h"
#include "mongo/db/matcher/extensions_callback_noop.h"
#include "mongo/db/query/collation/collator_interface.h"
#include "mongo/db/query/projection.h"
#include "mongo/db/query/query_request.h"

namespace mongo {

class OperationContext;

class CanonicalQuery {
public:
    // A type that encodes the notion of query shape. Essentialy a query's match, projection and
    // sort with the values taken out.
    typedef std::string QueryShapeString;

    /**
     * If parsing succeeds, returns a std::unique_ptr<CanonicalQuery> representing the parsed
     * query (which will never be NULL).  If parsing fails, returns an error Status.
     *
     * 'opCtx' must point to a valid OperationContext, but 'opCtx' does not need to outlive the
     * returned CanonicalQuery.
     *
     * Used for legacy find through the OP_QUERY message.
     */
    static StatusWith<std::unique_ptr<CanonicalQuery>> canonicalize(
        OperationContext* opCtx,
        const QueryMessage& qm,
        const boost::intrusive_ptr<ExpressionContext>& expCtx = nullptr,
        const ExtensionsCallback& extensionsCallback = ExtensionsCallbackNoop(),
        MatchExpressionParser::AllowedFeatureSet allowedFeatures =
            MatchExpressionParser::kDefaultSpecialFeatures);

    /**
     * If parsing succeeds, returns a std::unique_ptr<CanonicalQuery> representing the parsed
     * query (which will never be NULL).  If parsing fails, returns an error Status.
     *
     * 'opCtx' must point to a valid OperationContext, but 'opCtx' does not need to outlive the
     * returned CanonicalQuery.
     */
    static StatusWith<std::unique_ptr<CanonicalQuery>> canonicalize(
        OperationContext* opCtx,
        std::unique_ptr<QueryRequest> qr,
        const boost::intrusive_ptr<ExpressionContext>& expCtx = nullptr,
        const ExtensionsCallback& extensionsCallback = ExtensionsCallbackNoop(),
        MatchExpressionParser::AllowedFeatureSet allowedFeatures =
            MatchExpressionParser::kDefaultSpecialFeatures);

    /**
     * For testing or for internal clients to use.
     */

    /**
     * Used for creating sub-queries from an existing CanonicalQuery.
     *
     * 'root' must be an expression in baseQuery.root().
     *
     * Does not take ownership of 'root'.
     */
    static StatusWith<std::unique_ptr<CanonicalQuery>> canonicalize(OperationContext* opCtx,
                                                                    const CanonicalQuery& baseQuery,
                                                                    MatchExpression* root);

    /**
     * Returns true if "query" describes an exact-match query on _id.
     */
    static bool isSimpleIdQuery(const BSONObj& query);

    const NamespaceString& nss() const {
        return _qr->nss();
    }
    const std::string& ns() const {
        return _qr->nss().ns();
    }

    //
    // Accessors for the query
    //
    MatchExpression* root() const {
        return _root.get();
    }
    BSONObj getQueryObj() const {
        return _qr->getFilter();
    }
    const QueryRequest& getQueryRequest() const {
        return *_qr;
    }

    /**
     * Returns the projection, or nullptr if none.
     */
    const projection_ast::Projection* getProj() const {
        return _proj.get_ptr();
    }

    projection_ast::Projection* getProj() {
        return _proj.get_ptr();
    }

    const CollatorInterface* getCollator() const {
        return _collator.get();
    }

    /**
     * Returns a bitset indicating what metadata has been requested in the query.
     */
    const QueryMetadataBitSet& metadataDeps() const {
        return _metadataDeps;
    }

    /**
     * Allows callers to request metadata in addition to that needed as part of the query.
     */
    void requestAdditionalMetadata(const QueryMetadataBitSet& additionalDeps) {
        _metadataDeps |= additionalDeps;
    }

    /**
     * Compute the "shape" of this query by encoding the match, projection and sort, and stripping
     * out the appropriate values.
     */
    QueryShapeString encodeKey() const;

    /**
     * Sets this CanonicalQuery's collator, and sets the collator on this CanonicalQuery's match
     * expression tree.
     *
     * This setter can be used to override the collator that was created from the query request
     * during CanonicalQuery construction.
     */
    void setCollator(std::unique_ptr<CollatorInterface> collator);

    // Debugging
    std::string toString() const;
    std::string toStringShort() const;

    /**
     * Validates match expression, checking for certain
     * combinations of operators in match expression and
     * query options in QueryRequest.
     * Since 'root' is derived from 'filter' in QueryRequest,
     * 'filter' is not validated.
     *
     * TODO: Move this to query_validator.cpp
     */
    static Status isValid(MatchExpression* root, const QueryRequest& parsed);

    /**
     * Traverses expression tree post-order.
     * Sorts children at each non-leaf node by (MatchType, path(), children, number of children)
     */
    static void sortTree(MatchExpression* tree);

    /**
     * Returns a count of 'type' nodes in expression tree.
     */
    static size_t countNodes(const MatchExpression* root, MatchExpression::MatchType type);

    /**
     * Returns true if this canonical query may have converted extensions such as $where and $text
     * into no-ops during parsing. This will be the case if it allowed $where and $text in parsing,
     * but parsed using an ExtensionsCallbackNoop. This does not guarantee that a $where or $text
     * existed in the query.
     *
     * Queries with a no-op extension context are special because they can be parsed and planned,
     * but they cannot be executed.
     */
    bool canHaveNoopMatchNodes() const {
        return _canHaveNoopMatchNodes;
    }

    const boost::intrusive_ptr<ExpressionContext>& getExpCtx() const {
        return _expCtx;
    }

private:
    // You must go through canonicalize to create a CanonicalQuery.
    CanonicalQuery() {}

    Status init(OperationContext* opCtx,
                boost::intrusive_ptr<ExpressionContext> expCtx,
                std::unique_ptr<QueryRequest> qr,
                bool canHaveNoopMatchNodes,
                std::unique_ptr<MatchExpression> root,
                std::unique_ptr<CollatorInterface> collator);

    boost::intrusive_ptr<ExpressionContext> _expCtx;

    std::unique_ptr<QueryRequest> _qr;

    // _root points into _qr->getFilter()
    std::unique_ptr<MatchExpression> _root;

    boost::optional<projection_ast::Projection> _proj;

    // Keeps track of what metadata has been explicitly requested.
    QueryMetadataBitSet _metadataDeps;

    std::unique_ptr<CollatorInterface> _collator;

    bool _canHaveNoopMatchNodes = false;
};

}  // namespace mongo