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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.
*/
#pragma once
#include "mongo/db/query/canonical_query.h"
namespace mongo {
// Delimiters for canonical query portion of cache key encoding.
inline constexpr char kEncodeChildrenBegin = '[';
inline constexpr char kEncodeChildrenEnd = ']';
inline constexpr char kEncodeChildrenSeparator = ',';
inline constexpr char kEncodeProjectionRequirementSeparator = '-';
inline constexpr char kEncodeRegexFlagsSeparator = '/';
// A generic delimiter to separate encoded portions of the plan cache key. For example, used to
// separate the encoding of the collection, project, sort, flags, and pipeline sections. The
// delimiter must be included unconditionally even if the corresponding section of the encoded key
// will be empty.
inline constexpr char kEncodeSectionDelimiter = '|';
// These special bytes are used in the encoding of auto-parameterized match expressions in the SBE
// plan cache key.
// Precedes the id number of a parameter marker.
inline constexpr char kEncodeParamMarker = '?';
// Precedes the encoding of a constant when that constant has not been auto-paramterized. The
// constant is typically encoded as a BSON type byte followed by a BSON value (without the
// BSONElement's field name).
inline constexpr char kEncodeConstantLiteralMarker = ':';
// Precedes a byte which encodes the bounds tightness associated with a predicate. The structure of
// the plan (i.e. presence of filters) is affected by bounds tightness. Therefore, if different
// parameter values can result in different tightnesses, this must be explicitly encoded into the
// plan cache key.
inline constexpr char kEncodeBoundsTightnessDiscriminator = ':';
// Delimiters for the discriminator portion of the cache key encoding.
inline constexpr char kEncodeDiscriminatorsBegin = '<';
inline constexpr char kEncodeDiscriminatorsEnd = '>';
inline constexpr char kEncodeGlobalDiscriminatorsBegin = '(';
inline constexpr char kEncodeGlobalDiscriminatorsEnd = ')';
/**
* Returns true if the query predicate involves a negation of an EQ, LTE, or GTE comparison to
* 'null'.
*/
bool isQueryNegatingEqualToNull(const mongo::MatchExpression* tree);
namespace canonical_query_encoder {
/**
* Encode the given CanonicalQuery into a string representation which represents the shape of the
* query specifically for the classic plan cache. This is done by encoding the match, projection and
* sort and stripping the values from the match. Two queries with the same shape may not necessarily
* be able to use the same plan, so the plan cache has to add information to discriminate between
* queries with the same shape.
*/
CanonicalQuery::QueryShapeString encodeClassic(const CanonicalQuery& cq);
/**
* Encode the given CanonicalQuery into a string representation which represents the shape of the
* query for SBE plans. This is done by encoding the match, projection, sort and the FindCommand.
* Two queries with the same shape may not necessarily be able to use the same plan, so the
* plan cache has to add information to discriminate between queries with the same shape.
*/
CanonicalQuery::QueryShapeString encodeSBE(const CanonicalQuery& cq);
/**
* Encode the given CanonicalQuery into a string representation which represents the shape of the
* query for matching the query used with plan cache commands (planCacheClear, planCacheClearFilter,
* planCacheListFilters, and planCacheSetFilter). This is done by encoding the match, projection,
* sort and user-specified collation.
*/
CanonicalQuery::PlanCacheCommandKey encodeForPlanCacheCommand(const CanonicalQuery& cq);
/**
* Returns a hash of the given key (produced from either a QueryShapeString or a PlanCacheKey).
*/
uint32_t computeHash(StringData key);
} // namespace canonical_query_encoder
} // namespace mongo
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