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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#pragma once
#include <vespa/vespalib/stllike/string.h>
#include <vector>
#include <map>
namespace search::index { class Schema; }
namespace proton::matching {
/**
* A small utility class used to resolve views into fields when
* setting up the query tree. A view contains a set of fields. An
* undefined view is considered empty. A view will resolve to the set
* of fields it contains. If the view is empty, it will resolve to a
* field with the same name as the view itself.
**/
class ViewResolver
{
private:
using Map = std::map<vespalib::string, std::vector<vespalib::string> >;
Map _map;
public:
/**
* Add a field to the given view. This function is public to
* facilitate testing. Duplicate detection is not performed here,
* so adding the same field to a view multiple times is not a good
* idea.
*
* @return this object, for chaining
* @param view the name of the view
* @param field the name of the field
**/
ViewResolver &add(vespalib::stringref view,
vespalib::stringref field);
/**
* Resolve a view to obtain the set of fields it
* contains. Undefined views are considered empty and will resolve
* to a field with the same name as the view itself.
*
* @return true if the view was non-empty
* @param view the name of the view
* @param fields vector that will be filled out with the fields
* that are part of the requested view.
**/
bool resolve(vespalib::stringref view,
std::vector<vespalib::string> &fields) const;
/**
* Create a view resolver based on the field collections defined
* in the given schema. View definitions should be completely
* separate from how fields are combined into collections in the
* index, but this is a good start, as view and index correlate
* 1-to-1 in the current model.
*
* @return view resolver
* @param schema index schema
**/
static ViewResolver createFromSchema(const search::index::Schema &schema);
};
}
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