[jira] [Commented] (ARROW-474) Create an Arrow streaming file fomat

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

    [ https://issues.apache.org/jira/browse/ARROW-474?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15818747#comment-15818747 ] 

Wes McKinney commented on ARROW-474:
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Sounds good to me. This won't permit random access of batches, so not a replacement for the current file format, but very useful for streaming use cases as you describe. We have all the tools to implement this both in Java and C++ without a great of effort -- if we formalize the streaming format in the spec documents, then we can create initial implementations. We obviously will want to write integration tests for it. 

> Create an Arrow streaming file fomat
> ------------------------------------
>
>                 Key: ARROW-474
>                 URL: https://issues.apache.org/jira/browse/ARROW-474
>             Project: Apache Arrow
>          Issue Type: Improvement
>            Reporter: Nong Li
>
> It would be helpful to have a file/container layout that allows for streaming consumer and producers of arrow data.
> As a motivating example, a reader could have this API:
> Iterator<Record> read(java.io.InputStream source). 
> Similar a writer can have:
> void write(RecordBatch, java.io.OutputStream dest)
> The streams can be from a variety of sources: it be files, over the network, shared memory, pipe, etc. The layout would make it possible to implement
> both APIs without requiring intermediate buffering. 
> Speaking with Julien, this involves creating a simple container format similar to ARROW-264 but suitable for streaming consumer and producers. The layout in ARROW-264 has the schema at the end so can't be used in a streaming way. This format would likely be a rearranging of the current File layout pieces, something similar to:
> MAGIC, schema, totalBatches, (RecordBatchHeader, RecordBatchBody)*, MAGIC (or some end marker)
> totalBatches is optional for streaming producers that don't know.



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