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https://issues.apache.org/jira/browse/AVRO-160?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Doug Cutting updated AVRO-160:
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Attachment: AVRO-160.patch
Here's a patch that implements this for Java and updates the spec.
It's slightly different from what's proposed above. A file is a header
followed by zero or more blocks. These each contain:
- header
-- magic
-- metadata
-- sync
- block
-- length
-- data
-- sync
Thus every block is both preceded and followed by a sync marker.
I also split the Java data file reading code into two classes: a base class
that only permits sequential access, and a subclass that supports random
access. This will permit us to, e.g., process standard input.
> file format should be friendly to streaming
> -------------------------------------------
>
> Key: AVRO-160
> URL: https://issues.apache.org/jira/browse/AVRO-160
> Project: Avro
> Issue Type: Improvement
> Components: spec
> Reporter: Doug Cutting
> Assignee: Doug Cutting
> Attachments: AVRO-160.patch
>
>
> It should be possible to stream through an Avro data file without seeking to
> the end.
> Currently the interpretation is that schemas written to the file apply to all
> entries before them. If this were changed so that they instead apply to all
> entries that follow, and the initial schema is written at the start of the
> file, then streaming could be supported.
> Note that the only change permitted to a schema as a file is written is to,
> if it is a union, to add new branches at the end of that union. If it is not
> a union, no changes may be made. So it is still the case that the final
> schema in a file can read every entry in the file and thus may be used to
> randomly access the file.
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