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Fixing rounding errors when inserting microseconds #407
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When calculating nanoseconds since EPOCH, `total_seconds()` will give a float representation which when multiplied by 1e9 and cast to `int` will create rounding errors. E.g. inserting `2017-01-17T08:00:12.000001` with a datetime will produce `2017-01-17T08:00:12.000001024Z` in InfluxDB. This commit fixes this by never going via floating seconds, and is based on the `total_seconds()` function itself.
xginn8
suggested changes
Apr 22, 2017
influxdb/line_protocol.py
Outdated
| @@ -16,6 +16,12 @@ | |||
| EPOCH = UTC.localize(datetime.utcfromtimestamp(0)) | |||
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| def _to_nanos(timestamp): | |||
| delta = timestamp - EPOCH | |||
| nanos = (delta.days * 86400 + delta.seconds) * 10 ** 9 + delta.microseconds * 10 ** 3 | |||
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this line fails flake8 (89 chars), mind splitting it up? otherwise, this looks like a good change.
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The `_to_nanos` function had a line which was too long.
xginn8
approved these changes
May 7, 2017
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Just encountered this rounding error and was about to submit this very patch. In order to ensure that ns stays an int I would also rewrite: if precision is None or precision == 'n':
return ns
elif precision == 'u':
return ns / 1e3
elif precision == 'ms':
return ns / 1e6
elif precision == 's':
return ns / 1e9
elif precision == 'm':
return ns / 1e9 / 60
elif precision == 'h':
return ns / 1e9 / 3600to if precision is None or precision == 'n':
return ns
elif precision == 'u':
return ns / 10**3
elif precision == 'ms':
return ns / 10**6
elif precision == 's':
return ns / 10**9
elif precision == 'm':
return ns / 10**9 / 60
elif precision == 'h':
return ns / 10**9 / 3600 |
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It would probably allow you to close some of those: |
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Re-addressed in a new PR that merges this content including fixes from @clslgrnc |
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When calculating nanoseconds since EPOCH,
total_seconds()will give a float representation which when multiplied by 1e9 and cast tointwill create rounding errors. E.g. inserting2017-01-17T08:00:12.000001with a datetime will produce2017-01-17T08:00:12.000001024Zin InfluxDB. This commit fixes this by never going via floating seconds, and is based on thetotal_seconds()function itself.