Use fixed format for cache metas#20088
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ilevkivskyi merged 2 commits intopython:masterfrom Oct 20, 2025
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According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅ |
JukkaL
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Oct 20, 2025
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Nice! Did you see any measurable performance differences?
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I didn't do any precise measurements, on average of three warm runs |
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OK, after more careful measurements it is more like 4%, but still not nothing. Btw I also compared this PR vs 1.18.2, and warm |
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This makes cache meta files ~1.5x smaller. (I hoped together with previous diff it will give us 4x, but it is more like 3x). Implementation is mostly straightforward, here are some comments:
CacheMetaa regular class, it doesn't need to be immutable IMO (since we actually mutate it in few places).CacheMeta(note this might make JSON format slightly slower actually, but difference is below noise level)try/except (KeyError, ValueError)when deserializing metas.data_json/meta_jsonpaths todata_file/meta_fileeverywhere.