github.com/zuoyebang/bitalostable@v1.0.1-0.20240229032404-e3b99a834294/internal/batchskl/README.md (about)

     1  # batchskl
     2  
     3  Fast, non-concurrent skiplist implementation in Go that supports
     4  forward and backward iteration.
     5  
     6  ## Limitations
     7  
     8  * The interface is tailored for use in indexing bitalostable batches. Keys
     9    and values are stored outside of the skiplist making the skiplist
    10    awkward for general purpose use.
    11  * Deletion is not supported. Instead, higher-level code is expected to
    12    add deletion tombstones and needs to process those tombstones
    13    appropriately.
    14  
    15  ## Pedigree
    16  
    17  This code is based on Andy Kimball's arenaskl code.
    18  
    19  The arenaskl code is based on the skiplist found in Badger, a Go-based
    20  KV store:
    21  
    22  https://github.com/dgraph-io/badger/tree/master/skl
    23  
    24  The skiplist in Badger is itself based on a C++ skiplist built for
    25  Facebook's RocksDB:
    26  
    27  https://github.com/facebook/rocksdb/tree/master/memtable
    28  
    29  ## Benchmarks
    30  
    31  The benchmarks consist of a mix of reads and writes executed in parallel. The
    32  fraction of reads is indicated in the run name: "frac_X" indicates a run where
    33  X percent of the operations are reads.
    34  
    35  ```
    36  name                  time/op
    37  ReadWrite/frac_0      1.03µs ± 2%
    38  ReadWrite/frac_10     1.32µs ± 1%
    39  ReadWrite/frac_20     1.26µs ± 1%
    40  ReadWrite/frac_30     1.18µs ± 1%
    41  ReadWrite/frac_40     1.09µs ± 1%
    42  ReadWrite/frac_50      987ns ± 2%
    43  ReadWrite/frac_60     1.07µs ± 1%
    44  ReadWrite/frac_70      909ns ± 1%
    45  ReadWrite/frac_80      693ns ± 2%
    46  ReadWrite/frac_90      599ns ± 2%
    47  ReadWrite/frac_100    45.3ns ± 3%
    48  ```
    49  
    50  Forward and backward iteration are also fast:
    51  
    52  ```
    53  name                  time/op
    54  IterNext              4.49ns ± 3%
    55  IterPrev              4.48ns ± 3%
    56  ```