YugabyteDB (2.13.0.0-b42, bfc6a6643e7399ac8a0e81d06a3ee6d6571b33ab)

// Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.

// This source code is licensed under the BSD-style license found in the

// LICENSE file in the root directory of this source tree. An additional grant

// of patent rights can be found in the PATENTS file in the same directory.

// Copyright (c) 2012 The LevelDB Authors. All rights reserved.

// Use of this source code is governed by a BSD-style license that can be

// found in the LICENSE file. See the AUTHORS file for names of contributors.

//

// The following only applies to changes made to this file as part of YugaByte development.

//

// Portions Copyright (c) YugaByte, Inc.

//

// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except

// in compliance with the License.  You may obtain a copy of the License at

//

// http://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software distributed under the License

// is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express

// or implied.  See the License for the specific language governing permissions and limitations

// under the License.

//

// Class for specifying user-defined functions which perform a

// transformation on a slice.  It is not required that every slice

// belong to the domain and/or range of a function.  Subclasses should

// define InDomain and InRange to determine which slices are in either

// of these sets respectively.

#ifndef ROCKSDB_INCLUDE_ROCKSDB_SLICE_TRANSFORM_H

#define ROCKSDB_INCLUDE_ROCKSDB_SLICE_TRANSFORM_H

#include <string>

#include "yb/util/slice.h"

namespace rocksdb {

class SliceTransform {

 public:

  virtual ~SliceTransform() {}

  // Return the name of this transformation.

  virtual const char* Name() const = 0;

  // transform a src in domain to a dst in the range

  virtual Slice Transform(const Slice& src) const = 0;

  // determine whether this is a valid src upon the function applies

  virtual bool InDomain(const Slice& src) const = 0;

  // determine whether dst=Transform(src) for some src

  virtual bool InRange(const Slice& dst) const = 0;

  // Transform(s)=Transform(`prefix`) for any s with `prefix` as a prefix.

  //

  // This function is not used by RocksDB, but for users. If users pass

  // Options by string to RocksDB, they might not know what prefix extractor

  // they are using. This function is to help users can determine:

  //   if they want to iterate all keys prefixing `prefix`, whetherit is

  //   safe to use prefix bloom filter and seek to key `prefix`.

  // If this function returns true, this means a user can Seek() to a prefix

  // using the bloom filter. Otherwise, user needs to skip the bloom filter

  // by setting ReadOptions.total_order_seek = true.

  //

  // Here is an example: Suppose we implement a slice transform that returns

  // the first part of the string after spliting it using deimiter ",":

  // 1. SameResultWhenAppended("abc,") should return true. If aplying prefix

  //    bloom filter using it, all slices matching "abc:.*" will be extracted

  //    to "abc,", so any SST file or memtable containing any of those key

  //    will not be filtered out.

  // 2. SameResultWhenAppended("abc") should return false. A user will not

  //    guaranteed to see all the keys matching "abc.*" if a user seek to "abc"

  //    against a DB with the same setting. If one SST file only contains

  //    "abcd,e", the file can be filtered out and the key will be invisible.

  //

  // i.e., an implementation always returning false is safe.

  virtual bool SameResultWhenAppended(const Slice& prefix) const {

    return false;

  }

};

extern const SliceTransform* NewFixedPrefixTransform(size_t prefix_len);

extern const SliceTransform* NewCappedPrefixTransform(size_t cap_len);

extern const SliceTransform* NewNoopTransform();

} // namespace rocksdb

#endif // ROCKSDB_INCLUDE_ROCKSDB_SLICE_TRANSFORM_H