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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
/**
* \class document::BucketSelector
* \ingroup bucket
*
* \brief Calculates which buckets correspond to a document selection.
*
* When you want to visit a subset of documents in VDS you specify a
* document selection expression. Some of these expressions limit what
* buckets may contain matching documents.
*
* This class is used to calculate which set of buckets we need to visit
* to be sure we find all existing data.
*
* \see BucketId For more information on buckets
* \see document::select::Parser For more information about the selection
* language
*/
#pragma once
#include <memory>
#include <vector>
namespace document {
namespace select {
class Node;
}
class BucketId;
class BucketIdFactory;
class BucketSelector {
const BucketIdFactory& _factory;
public:
explicit BucketSelector(const BucketIdFactory& factory);
using BucketVector = std::vector<BucketId>;
/**
* Get a list of bucket ids that needs to be visited to be sure to find
* all data matching given expression. Note that we can only detect
* some common expressions. We guarantuee that you get all buckets
* that may contain data, but not that you get the minimal bucket set.
*
* If a small bucket set can not be identified, a null pointer is returned
* to indicate all buckets needs to be visited.
*/
std::unique_ptr<BucketVector> select(const select::Node& expression) const;
};
} // document
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