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https://issues.apache.org/jira/browse/ARROW-1860?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16337899#comment-16337899
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Wes McKinney commented on ARROW-1860:
-------------------------------------
I'm running into a slight issue with this refactoring around output streams
which are currently at a position that is not a multiple of 8.
see
https://github.com/apache/arrow/blob/master/cpp/src/arrow/ipc/metadata-internal.cc#L903
This results in the entire message payload being non-deterministic depending on
the state of the OutputStream. I don't think it will impact any applications,
but I suggest we write padding bytes at the _start_ to an 8-byte offset and
then begin writing the message. This is the same approach used by
{{WriteTensor}} in
https://github.com/apache/arrow/blob/master/cpp/src/arrow/ipc/writer.cc#L621.
[~robertnishihara] [~pcmoritz] [~xhochy] does this seem reasonable?
> [C++] Add data structure to "stage" a sequence of IPC messages from in-memory
> data
> ----------------------------------------------------------------------------------
>
> Key: ARROW-1860
> URL: https://issues.apache.org/jira/browse/ARROW-1860
> Project: Apache Arrow
> Issue Type: New Feature
> Components: C++
> Reporter: Wes McKinney
> Assignee: Wes McKinney
> Priority: Major
> Fix For: 0.9.0
>
> Attachments: text.html
>
>
> Currently, when you need to pre-allocate space for a record batch or a stream
> (schema + dictionaries + record batches), you must make multiple passes over
> the data structures of interest (and use e.g. {{MockOutputStream}} to compute
> the size of the output buffer). It would be useful to make a single pass to
> "prepare" the IPC payload for both sizing and writing to prevent having to
> make multiple passes
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