Tz_world / timezone_boundary_builder update

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I have refactored tz_world to separate different backend strategies. Please feel free to give it a try, I plan to release a new version on hex later this week.

New Backend Access modules

  • TzWorld.Backend.Memory which retains all data in memory for fastest performance at the expense of using approximately 1Gb of memory
  • TzWorld.Backend.Dets which uses Erlang’s :dets data store. This uses negligible memory at the expense of slow access times (approximaltey 500ms in testing)
  • TzWorld.Backend.DetsWithIndexCache which balances memory usage and performance. This backend is recommended in most situations since its performance is similar to TzWorld.Backend.Memory (about 5% slower in testing) and uses about 25Mb of memory
  • TzWorld.Backend.Ets which uses :ets for storage. With the default settings of :compressed for the :ets table its memory consumption is about 512Mb but with access that is over 20 times slower than TzWorld.Backend.DetsWithIndexCache

Most interesting is that by caching the bounding boxes in memory, the backend TzWorld.Backend.DetsWithIndexCache looks to be a good balance of memory utilisation and performance. It uses only ~20Mb of memory to store the bounding boxes and has performance similar to the in-memory backend.

Basic Benchmark

Name                                 ips        average  deviation         median         99th %
Backend Memory                     52.34       19.10 ms    ±14.86%       18.34 ms       30.62 ms
Backend DetsWithIndexCache         50.10       19.96 ms    ±13.15%       20.79 ms       24.66 ms
Backend Ets                         2.33      428.53 ms     ±2.51%      432.73 ms      441.58 ms
Backend Dets                        0.59     1693.80 ms     ±9.62%     1646.47 ms     2018.27 ms

Comparison: 
Backend Memory                     52.34
Backend DetsWithIndexCache         50.10 - 1.04x slower +0.85 ms
Backend Ets                         2.33 - 22.43x slower +409.43 ms
Backend Dets                        0.59 - 88.66x slower +1674.70 ms
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