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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
/**
* Iterates metadata in the bucket using the SPI, and analyze where we need to
* split in order to split the bucket in two pieces. Possible results include.
*
* - Normal case: A set of two buckets (with same used bits count),
* splitting source bucket in half.
* - Empty source bucket. No data to split.
* - Error: Impossible to split data in two. All data has common bucket bits.
* - Single target split: Asked to limit bits used to less than max, and using
* this amount of bits won't split data in two. Currently, we return this
* as success and create the paired bucket, such that SPI can handle single
* target split just as a regular split, only that no data will actually be
* split into the other target. (And that target thus must be deleted
* afterwards if empty.)
*
*/
#pragma once
#include <vespa/persistence/spi/bucket.h>
#include <vespa/persistence/spi/context.h>
#include <vespa/vespalib/util/printable.h>
namespace storage {
namespace spi { struct PersistenceProvider; }
struct SplitBitDetector
{
enum ResultType {
OK,
EMPTY,
ERROR
};
class Result : public vespalib::Printable {
ResultType _result;
document::BucketId _target1;
document::BucketId _target2;
vespalib::string _reason;
bool _singleTarget;
public:
Result() : _result(EMPTY), _singleTarget(false) {}
Result(vespalib::stringref error)
: _result(ERROR), _reason(error), _singleTarget(false) {}
Result(const document::BucketId& t1, const document::BucketId& t2,
bool single)
: _result(OK), _target1(t1), _target2(t2), _singleTarget(single) {}
bool success() const { return (_result == OK); }
bool failed() const { return (_result == ERROR); }
bool empty() const { return (_result == EMPTY); }
const vespalib::string& getReason() const { return _reason; }
const document::BucketId& getTarget1() const { return _target1; }
const document::BucketId& getTarget2() const { return _target2; }
// Printable implementation
void print(std::ostream& out, bool verbose, const std::string& indent) const override;
};
static Result detectSplit(spi::PersistenceProvider&, const spi::Bucket&,
uint32_t maxSplitBits, spi::Context&,
uint32_t minCount = 0, uint32_t minSize = 0);
};
} // storage
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