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/**
* Copyright (C) 2019-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 <bitset>
#include "mongo/db/exec/projection_executor.h"
#include "mongo/db/query/projection_ast.h"
namespace mongo::projection_executor {
/**
* Various parameters which control the behaviour of the projection executor builder.
*/
enum BuilderParams : char {
/**
* Indicates whether the 'optimize()' method needs to be called on the newly created executor
* before returning it to the caller.
*
* Start from 1 so that these values can be stored in a bitset.
*/
kOptimizeExecutor = 1,
/**
* Pass this parameter to the projection executor builder if fast-path projection execution is
* allowed. The caller can disable the fast-path, but is never required to do so for correctness
* since it will be disabled internally for correctness as needed.
*
* Note that this setting is just a hint to the projection executor builder and does not
* guarantee that the fast-path projection executor will be created. The fast path executor will
* only be created for certain types of projections, and the fast path may only be used for
* Documents which are trivially convertible to BSON.
*
* Moreover, even if the projection executor is created with the fast-path enabled, the decision
* whether to use the fast-path or not is made on document-by-document basis. So, if applying a
* fast-path projection is not possible, the executor will fall back to the default
* implementation.
*/
kAllowFastPath,
/**
* An internal value holding the total number of projection executor builder parameters.
* New parameters must be added before the kNumParams sentinel.
*/
kNumParams
};
using BuilderParamsBitSet = std::bitset<BuilderParams::kNumParams>;
/**
* By default all projection executor builder parameters are turned on.
*/
static constexpr auto kDefaultBuilderParams =
BuilderParamsBitSet(~(1 << BuilderParams::kNumParams));
/**
* Builds a projection execution tree from the given 'projection' and using the given projection
* 'policies' by walking an AST tree starting at the root node stored within the 'projection'.
* The 'params' parameter is used to pass various control parameters to alter the behaviour of the
* projection executor builder.
*/
std::unique_ptr<ProjectionExecutor> buildProjectionExecutor(
boost::intrusive_ptr<ExpressionContext> expCtx,
const projection_ast::Projection* projection,
ProjectionPolicies policies,
BuilderParamsBitSet params);
} // namespace mongo::projection_executor
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