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56 lines
2.8 KiB
56 lines
2.8 KiB
1 year ago
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// Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
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// This source code is licensed under both the GPLv2 (found in the
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// COPYING file in the root directory) and Apache 2.0 License
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// (found in the LICENSE.Apache file in the root directory).
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#pragma once
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#include "rocksdb/table_properties.h"
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namespace ROCKSDB_NAMESPACE {
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// Computes a stable, universally unique 128-bit (16 binary char) identifier
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// for an SST file from TableProperties. This is supported for table (SST)
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// files created with RocksDB 6.24 and later. NotSupported will be returned
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// for other cases. The first 16 bytes (128 bits) is of sufficient quality
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// for almost all applications, and shorter prefixes are usable as a
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// hash of the full unique id.
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//
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// Note: .c_str() is not compatible with binary char strings, so using
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// .c_str() on the result will often result in information loss and very
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// poor uniqueness probability.
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//
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// More detail: the value is *guaranteed* unique for SST files
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// generated in the same process (even different DBs, RocksDB >= 6.26),
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// and first 128 bits are guaranteed not "all zeros" (RocksDB >= 6.26)
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// so that the "all zeros" value can be used reliably for a null ID.
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// These IDs are more than sufficient for SST uniqueness within each of
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// many DBs or hosts. For an extreme example assuming random IDs, consider
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// 10^9 hosts each with 10^9 live SST files being replaced at 10^6/second.
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// Such a service would need to run for 10 million years to see an ID
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// collision among live SST files on any host.
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//
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// And assuming one generates many SST files in the lifetime of each process,
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// the probability of ID collisions is much "better than random"; see
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// https://github.com/pdillinger/unique_id
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Status GetUniqueIdFromTableProperties(const TableProperties &props,
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std::string *out_id);
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// Computes a 192-bit (24 binary char) stable, universally unique ID
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// with an extra 64 bits of uniqueness compared to the standard ID. It is only
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// appropriate to use this ID instead of the 128-bit ID if ID collisions
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// between files among any hosts in a vast fleet is a problem, such as a shared
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// global namespace for SST file backups. Under this criteria, the extreme
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// example above would expect a global file ID collision every 4 days with
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// 128-bit IDs (using some worst-case assumptions about process lifetime).
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// It's 10^17 years with 192-bit IDs.
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Status GetExtendedUniqueIdFromTableProperties(const TableProperties &props,
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std::string *out_id);
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// Converts a binary string (unique id) to hexadecimal, with each 64 bits
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// separated by '-', e.g. 6474DF650323BDF0-B48E64F3039308CA-17284B32E7F7444B
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// Also works on unique id prefix.
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std::string UniqueIdToHumanString(const std::string &id);
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} // namespace ROCKSDB_NAMESPACE
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