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https://issues.apache.org/jira/browse/BEAM-12730?focusedWorklogId=665769&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-665769
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ASF GitHub Bot logged work on BEAM-12730:
-----------------------------------------
Author: ASF GitHub Bot
Created on: 17/Oct/21 00:31
Start Date: 17/Oct/21 00:31
Worklog Time Spent: 10m
Work Description: nikie commented on a change in pull request #15667:
URL: https://github.com/apache/beam/pull/15667#discussion_r730046514
##########
File path: sdks/python/apache_beam/io/textio.py
##########
@@ -561,6 +570,7 @@ def __init__(
skipped from each source file. Must be 0 or higher. Large number of
skipped lines might impact performance.
coder (~apache_beam.coders.coders.Coder): Coder used to decode each line.
+ delimiter (str or bytes): delimiter to split records
Review comment:
@dmitriikuzinepam
What happens if `readbuffer` ends in the middle of a multi-byte delimiter?
This line `current_pos = len(read_buffer.data)` together with `next_lf =
read_buffer.data.find(self._delimiter, current_pos)` on next iteration might
skip such delimiter.
Also, it looks like Java SDK's TextIO behaves differently in case if
delimiter is not set: it uses both `\n` and `\r\n` delimiters only in case if
delimiter is not provided. If it is provided - it looks only for the explicit
delimiter, see:
https://github.com/apache/beam/blob/52a178f0a66829bbd1d99fcaf70921a8bd9300f6/sdks/java/core/src/main/java/org/apache/beam/sdk/io/TextSource.java#L189,
https://github.com/apache/beam/blob/master/sdks/java/core/src/main/java/org/apache/beam/sdk/io/TextSource.java#L208
##########
File path: sdks/python/apache_beam/io/textio.py
##########
@@ -561,6 +570,7 @@ def __init__(
skipped from each source file. Must be 0 or higher. Large number of
skipped lines might impact performance.
coder (~apache_beam.coders.coders.Coder): Coder used to decode each line.
+ delimiter (str or bytes): delimiter to split records
Review comment:
@dmitriikuzinepam
What happens if `readbuffer` ends in the middle of a multi-byte delimiter?
This line `current_pos = len(read_buffer.data)` together with `next_lf =
read_buffer.data.find(self._delimiter, current_pos)` on next iteration might
skip such delimiter.
Also, it looks like Java SDK's TextIO behaves differently in case if
delimiter is not set: it uses both `\n` and `\r\n` delimiters only in case if
delimiter is not provided. If it is provided - it looks only for the explicit
delimiter, see:
https://github.com/apache/beam/blob/52a178f0a66829bbd1d99fcaf70921a8bd9300f6/sdks/java/core/src/main/java/org/apache/beam/sdk/io/TextSource.java#L189,
https://github.com/apache/beam/blob/52a178f0a66829bbd1d99fcaf70921a8bd9300f6/sdks/java/core/src/main/java/org/apache/beam/sdk/io/TextSource.java#L208
##########
File path: sdks/python/apache_beam/io/textio.py
##########
@@ -561,6 +570,7 @@ def __init__(
skipped from each source file. Must be 0 or higher. Large number of
skipped lines might impact performance.
coder (~apache_beam.coders.coders.Coder): Coder used to decode each line.
+ delimiter (str or bytes): delimiter to split records
Review comment:
@dmitriikuzinepam
What happens if `readbuffer` ends in the middle of a multi-byte delimiter?
This line `current_pos = len(read_buffer.data)` together with `next_lf =
read_buffer.data.find(self._delimiter, current_pos)` on next iteration might
skip such delimiter.
Also, it looks like Java SDK's TextIO behaves differently in case if
delimiter is not set: it uses both `\n` and `\r\n` delimiters only in case if
delimiter is not provided. If it is provided - it looks only for the explicit
delimiter, see:
https://github.com/apache/beam/blob/52a178f0a66829bbd1d99fcaf70921a8bd9300f6/sdks/java/core/src/main/java/org/apache/beam/sdk/io/TextSource.java#L189,
https://github.com/apache/beam/blob/52a178f0a66829bbd1d99fcaf70921a8bd9300f6/sdks/java/core/src/main/java/org/apache/beam/sdk/io/TextSource.java#L208
Actually, the default for the delimiter `delimiter=b'\n',` is a bit
misleading, since under the hood it continues to split on both `\n` and `\r\n`
currently.
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Issue Time Tracking
-------------------
Worklog Id: (was: 665769)
Time Spent: 7h 10m (was: 7h)
> Add custom delimiters to Python TextIO reads
> --------------------------------------------
>
> Key: BEAM-12730
> URL: https://issues.apache.org/jira/browse/BEAM-12730
> Project: Beam
> Issue Type: New Feature
> Components: io-py-common, io-py-files
> Reporter: Daniel Oliveira
> Assignee: Dmitrii Kuzin
> Priority: P2
> Labels: beginner, newbie, starter
> Time Spent: 7h 10m
> Remaining Estimate: 0h
>
> A common request by users is to be able to separate a text files read by
> TextIO with delimiters other than newline. The Java SDK already supports this
> feature.
> The current delimiter code is [located
> here|https://github.com/apache/beam/blob/v2.31.0/sdks/python/apache_beam/io/textio.py#L236]
> and defaults to newlines. This function could easily be modified to also
> handle custom delimiters. Changing this would also necessitate changing the
> API for the various TextIO.Read methods and adding documentation.
> This seems like a good starter bug for making more in-depth contributions to
> Beam Python.
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