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https://issues.apache.org/jira/browse/ARROW-3667?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Paul Taylor updated ARROW-3667:
-------------------------------
Comment: was deleted
(was: Issue resolved by pull request 3787
[https://github.com/apache/arrow/pull/3787])
> [JS] Incorrectly reads record batches with an all null column
> -------------------------------------------------------------
>
> Key: ARROW-3667
> URL: https://issues.apache.org/jira/browse/ARROW-3667
> Project: Apache Arrow
> Issue Type: Bug
> Affects Versions: JS-0.3.1
> Reporter: Brian Hulette
> Assignee: Paul Taylor
> Priority: Major
> Fix For: JS-0.5.0, JS-0.4.1
>
>
> The JS library seems to incorrectly read any columns that come after an
> all-null column in IPC buffers produced by pyarrow.
> Here's a python script that generates two arrow buffers, one with an all-null
> column followed by a utf-8 column, and a second with those two reversed
> {code:python}
> import pyarrow as pa
> import pandas as pd
> def serialize_to_arrow(df, fd, compress=True):
> batch = pa.RecordBatch.from_pandas(df)
> writer = pa.RecordBatchFileWriter(fd, batch.schema)
> writer.write_batch(batch)
> writer.close()
> if __name__ == "__main__":
> df = pd.DataFrame(data={'nulls': [None, None, None], 'not nulls': ['abc',
> 'def', 'ghi']}, columns=['nulls', 'not nulls'])
> with open('bad.arrow', 'wb') as fd:
> serialize_to_arrow(df, fd)
> df = pd.DataFrame(df, columns=['not nulls', 'nulls'])
> with open('good.arrow', 'wb') as fd:
> serialize_to_arrow(df, fd)
> {code}
> JS incorrectly interprets the [null, not null] case:
> {code:javascript}
> > var arrow = require('apache-arrow')
> undefined
> > var fs = require('fs')
> undefined
> > arrow.Table.from(fs.readFileSync('good.arrow')).getColumn('not
> > nulls').get(0)
> 'abc'
> > arrow.Table.from(fs.readFileSync('bad.arrow')).getColumn('not nulls').get(0)
> '\u0000\u0000\u0000\u0000\u0003\u0000\u0000\u0000\u0006\u0000\u0000\u0000\t\u0000\u0000\u0000'
> {code}
> Presumably this is because pyarrow is omitting some (or all) of the buffers
> associated with the all-null column, but the JS IPC reader is still looking
> for them, causing the buffer count to get out of sync.
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