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https://issues.apache.org/jira/browse/ARROW-2026?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16616320#comment-16616320
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Wes McKinney commented on ARROW-2026:
-------------------------------------
Patches welcome
> [Python] µs timestamps saved as int64 even if
> use_deprecated_int96_timestamps=True
> ----------------------------------------------------------------------------------
>
> Key: ARROW-2026
> URL: https://issues.apache.org/jira/browse/ARROW-2026
> Project: Apache Arrow
> Issue Type: Bug
> Components: Python
> Affects Versions: 0.8.0
> Environment: OS: Mac OS X 10.13.2
> Python: 3.6.4
> PyArrow: 0.8.0
> Reporter: Diego Argueta
> Priority: Major
> Labels: redshift, timestamps
> Fix For: 0.12.0
>
>
> When writing to a Parquet file, if `use_deprecated_int96_timestamps` is True,
> timestamps are only written as 96-bit integers if the timestamp has
> nanosecond resolution. This is a problem because Amazon Redshift timestamps
> only have microsecond resolution but require them to be stored in 96-bit
> format in Parquet files.
> I'd expect the use_deprecated_int96_timestamps flag to cause _all_ timestamps
> to be written as 96 bits, regardless of resolution. If this is a deliberate
> design decision, it'd be immensely helpful if it were explicitly documented
> as part of the argument.
>
> To reproduce:
>
> 1. Create a table with a timestamp having microsecond or millisecond
> resolution, and save it to a Parquet file. Be sure to set
> `use_deprecated_int96_timestamps` to True.
>
> {code:java}
> import datetime
> import pyarrow
> from pyarrow import parquet
> schema = pyarrow.schema([
> pyarrow.field('last_updated', pyarrow.timestamp('us')),
> ])
> data = [
> pyarrow.array([datetime.datetime.now()], pyarrow.timestamp('us')),
> ]
> table = pyarrow.Table.from_arrays(data, ['last_updated'])
> with open('test_file.parquet', 'wb') as fdesc:
> parquet.write_table(table, fdesc,
> use_deprecated_int96_timestamps=True)
> {code}
>
> 2. Inspect the file. I used parquet-tools:
>
> {noformat}
> dak@tux ~ $ parquet-tools meta test_file.parquet
> file: file:/Users/dak/test_file.parquet
> creator: parquet-cpp version 1.3.2-SNAPSHOT
> file schema: schema
> --------------------------------------------------------------------------------
> last_updated: OPTIONAL INT64 O:TIMESTAMP_MICROS R:0 D:1
> row group 1: RC:1 TS:76 OFFSET:4
> --------------------------------------------------------------------------------
> last_updated: INT64 SNAPPY DO:4 FPO:28 SZ:76/72/0.95 VC:1
> ENC:PLAIN,PLAIN_DICTIONARY,RLE{noformat}
>
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