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/**
* Copyright (C) 2018 MongoDB 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 <set>
#include "mongo/db/field_ref.h"
#include "mongo/db/index/multikey_paths.h"
#include "mongo/db/query/index_bounds_builder.h"
#include "mongo/db/query/query_solution.h"
namespace mongo {
namespace wildcard_planning {
using BoundsTightness = IndexBoundsBuilder::BoundsTightness;
/**
* Specifies the maximum depth of nested array indices through which a query may traverse before a
* $** declines to answer it, due to the exponential complexity of the bounds required.
*/
static constexpr size_t kWildcardMaxArrayIndexTraversalDepth = 8u;
/**
* Returns a MultikeyPaths which indicates which components of 'indexedPath' are multikey, by
* looking up multikeyness in 'multikeyPathSet'.
*/
MultikeyPaths buildMultiKeyPathsForExpandedWildcardIndexEntry(
const FieldRef& indexedPath, const std::set<FieldRef>& multikeyPathSet);
/**
* Given a query path and the set of known multikey path components, this function outputs the power
* set of paths generated by considering each relevant numerical path component first as a literal
* fieldname, and then as an array index. In other words, for each numerical path component that
* immediately follows a multikey field, we will output one path with the numerical component and
* one path without. If both 'a' and 'b' are multikey, then the queryPath 'a.0.b.1.c' will produce
* ['a.0.b.1.c', 'a.0.b.c', 'a.b.1.c', 'a.b.c'].
*/
std::set<FieldRef> generateFieldNameOrArrayIndexPathSet(const std::set<std::size_t>& multikeyPaths,
const FieldRef& queryPath);
/**
* In certain circumstances, it is necessary to adjust the tightness of the bounds generated by the
* planner for $** indexes. For instance, if the query traverses through one or more arrays via
* specific indices, then we must enforce INEXACT_FETCH to ensure correctness, regardless of the
* predicate. Given an IndexEntry representing an expanded $** index, we apply any necessary changes
* to the tightness here.
*/
BoundsTightness applyWildcardIndexScanBoundsTightness(const IndexEntry& index,
BoundsTightness tightnessIn);
/**
* Returns false if 'queryPath' includes any numerical path components which render it unanswerable
* by the $** index, true otherwise. Specifically, the $** index cannot answer the query if either
* of the following scenarios occur:
*
* - The query path traverses through more than 'kWildcardMaxArrayIndexTraversalDepth' nested arrays
* via explicit array indices.
* - The query path lies along a $** projection through an array index.
*
* For an example of the latter case, say that our query path is 'a.0.b', our projection includes
* {'a.0': 1}, and 'a' is multikey. The query semantics will match 'a.0.b' by either field name or
* array index against the documents, but because the $** index always projects numeric path
* components strictly as field names, the projection {'a.0': 1} cannot correctly support this
* query.
*
* To see why, consider the document {a: [1, 2, 3]}. Query {'a.0': 1} will match this document, but
* the projection {'a.0': 1} will produce output document {a: []}, and so we will not index any of
* the values [1, 2, 3] for 'a'.
*/
bool validateNumericPathComponents(const MultikeyPaths& multikeyPaths,
const std::set<FieldRef>& includedPaths,
const FieldRef& queryPath);
} // namespace wildcard_planning
} // namespace mongo
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