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

// This source code is licensed under both the GPLv2 (found in the

// COPYING file in the root directory) and Apache 2.0 License

// (found in the LICENSE.Apache file in the root directory).

package org.rocksdb;

/**

* IndexType used in conjunction with BlockBasedTable.

*/

public enum IndexType {

/**

* A space efficient index block that is optimized for

* binary-search-based index.

*/

kBinarySearch((byte) 0),

/**

* The hash index, if enabled, will do the hash lookup when

* {@code Options.prefix_extractor} is provided.

*/

kHashSearch((byte) 1),

/**

* A two-level index implementation. Both levels are binary search indexes.

*/

kTwoLevelIndexSearch((byte) 2),

/**

* Like {@link #kBinarySearch}, but index also contains first key of each block.

* This allows iterators to defer reading the block until it's actually

* needed. May significantly reduce read amplification of short range scans.

* Without it, iterator seek usually reads one block from each level-0 file

* and from each level, which may be expensive.

* Works best in combination with:

* - IndexShorteningMode::kNoShortening,

* - custom FlushBlockPolicy to cut blocks at some meaningful boundaries,

* e.g. when prefix changes.

* Makes the index significantly bigger (2x or more), especially when keys

* are long.

*/

kBinarySearchWithFirstKey((byte) 3);

/**

* Returns the byte value of the enumerations value

*

* @return byte representation

*/

public byte getValue() {

return value_;

}

IndexType(final byte value) {

value_ = value;

}

private final byte value_;

}