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57 lines
1.6 KiB
Markdown
57 lines
1.6 KiB
Markdown
# batchskl
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Fast, non-concurrent skiplist implementation in Go that supports
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forward and backward iteration.
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## Limitations
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* The interface is tailored for use in indexing pebble batches. Keys
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and values are stored outside of the skiplist making the skiplist
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awkward for general purpose use.
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* Deletion is not supported. Instead, higher-level code is expected to
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add deletion tombstones and needs to process those tombstones
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appropriately.
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## Pedigree
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This code is based on Andy Kimball's arenaskl code.
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The arenaskl code is based on the skiplist found in Badger, a Go-based
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KV store:
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https://github.com/dgraph-io/badger/tree/master/skl
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The skiplist in Badger is itself based on a C++ skiplist built for
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Facebook's RocksDB:
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https://github.com/facebook/rocksdb/tree/master/memtable
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## Benchmarks
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The benchmarks consist of a mix of reads and writes executed in parallel. The
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fraction of reads is indicated in the run name: "frac_X" indicates a run where
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X percent of the operations are reads.
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```
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name time/op
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ReadWrite/frac_0 1.03µs ± 2%
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ReadWrite/frac_10 1.32µs ± 1%
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ReadWrite/frac_20 1.26µs ± 1%
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ReadWrite/frac_30 1.18µs ± 1%
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ReadWrite/frac_40 1.09µs ± 1%
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ReadWrite/frac_50 987ns ± 2%
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ReadWrite/frac_60 1.07µs ± 1%
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ReadWrite/frac_70 909ns ± 1%
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ReadWrite/frac_80 693ns ± 2%
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ReadWrite/frac_90 599ns ± 2%
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ReadWrite/frac_100 45.3ns ± 3%
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```
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Forward and backward iteration are also fast:
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```
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name time/op
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IterNext 4.49ns ± 3%
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IterPrev 4.48ns ± 3%
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```
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