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https://issues.apache.org/jira/browse/AVRO-465?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12845405#action_12845405
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Matt Massie commented on AVRO-465:
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Jeff-
I'd like to understand this problem a little better. The C implementation
shouldn't require you know the file schema ahead of time.
If you pass in NULL for the reader's schema, then the writer's schema will be
used. This is a documentation bug since I don't explicitly explain this
anywhere.
Can you please try to read the data file with the reader's schema set to NULL?
Btw, the relevant code is in datum_read.c around line 303
{code}
if (readers_schema == NULL) {
readers_schema = writers_schema;
} else if (!avro_schema_match(writers_schema, readers_schema)) {
return EINVAL;
}
{code}
> C implementation requires you to know a file's schema before reading
> --------------------------------------------------------------------
>
> Key: AVRO-465
> URL: https://issues.apache.org/jira/browse/AVRO-465
> Project: Avro
> Issue Type: Bug
> Components: c
> Affects Versions: 1.3.0
> Reporter: Jeff Hodges
> Attachments: AVRO-465-schema_for_reader.patch
>
>
> The C implementation gives the user no way of reading the objects in a data
> file without knowing the file's schema ahead of time.
> While it does fill in the writers_schema part of the avro_file_reader_t on
> read, this field is not available to the API as it is left out of avro.h. Two
> options persent itself: 1) preserve the API as is and add a
> avro_schema_from_file_reader() function or 2) move the avro_file_reader_t and
> avro_file_writer_t structs to avro.h.
> A third option, that I don't approve of, is providing a function that reads
> from a datafile but uses the writers_schema in the reader given instead of
> requiring another schema to be passed into it. This is problematic because
> anyone using the API would have fewer debugging and testing options when
> dealing with interop datasets. Any problem that occurs might just be the
> schema in the file being off, or whatever.
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