[jira] [Updated] (ARROW-1957) [Python] Write nanosecond timestamps using new NANO LogicalType Parquet unit

["Wes McKinney (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ARROW-1957?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Wes McKinney updated ARROW-1957:
--------------------------------
    Fix Version/s: 0.14.0

> [Python] Write nanosecond timestamps using new NANO LogicalType Parquet unit
> ----------------------------------------------------------------------------
>
>                 Key: ARROW-1957
>                 URL: https://issues.apache.org/jira/browse/ARROW-1957
>             Project: Apache Arrow
>          Issue Type: Improvement
>          Components: Python
>    Affects Versions: 0.8.0
>         Environment: Python 3.6.4.  Mac OSX and CentOS Linux release 7.3.1611.  Pandas 0.21.1 .
>            Reporter: Jordan Samuels
>            Priority: Minor
>              Labels: parquet
>             Fix For: 0.14.0
>
>
> The following code
> {code}
> import pyarrow as pa
> import pyarrow.parquet as pq
> import pandas as pd
> n=3
> df = pd.DataFrame({'x': range(n)}, index=pd.DatetimeIndex(start='2017-01-01', freq='1n', periods=n))
> pq.write_table(pa.Table.from_pandas(df), '/tmp/t.parquet'){code}
> results in:
> {{ArrowInvalid: Casting from timestamp[ns] to timestamp[us] would lose data: 1483228800000000001}}
> The desired effect is that we can save nanosecond resolution without losing precision (e.g. conversion to ms).  Note that if {{freq='1u'}} is used, the code runs properly.



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