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https://issues.apache.org/jira/browse/AVRO-986?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Douglas Creager updated AVRO-986:
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Attachment: 0001-avromod-utility.patch
Here's a patch that adds a new "avromod" command-line utility. It can be used
as a fixup script to remove the avro.sync field from the header (once I commit
Michael's patch). It's also useful in its own right since you can create
copies of Avro files with different compression codecs and block sizes.
Eventually, we can also add options for changing the schema of the data in the
file.
> Avro files generated from avro-c dont work with the Java mapred
> implementation.
> -------------------------------------------------------------------------------
>
> Key: AVRO-986
> URL: https://issues.apache.org/jira/browse/AVRO-986
> Project: Avro
> Issue Type: Bug
> Components: c, java
> Environment: avro-c 1.6.2-SNAPSHOT
> avro-java 1.6.2-SNAPSHOT
> hadoop 0.20.2
> Reporter: Michael Cooper
> Priority: Critical
> Labels: c, hadoop, java, mapreduce
> Attachments: 0001-Remove-sync-marker-from-metadata-in-header.patch,
> 0001-avromod-utility.patch, AVRO-986-java.patch, quickstop.db
>
>
> When a file generated from the Avro-C implementation is fed into Hadoop, it
> will fail with "Block size invalid or too large for this implementation: -49".
> This is caused by the sync marker, namely the one that Avro-C puts into the
> header...
> The org.apache.avro.mapred.AvroRecordReader uses a FileSplit object to work
> out where it should read from, but this class is not particularly smart, it
> just divides the file up into equal size chunks, the first being with
> position 0.
> So org.apache.avro.mapred.AvroRecordReader gets 0 as the start of its chunk,
> and calls
> {code:title=AvroRecordReader.java}reader.sync(split.getStart()); // sync to
> start{code}
> Then the org.apache.avro.file.DataFileReader::seek() goes to 0, then searches
> for a sync marker....
> It encounters one at position 32, the one in the header metadata map,
> "avro.sync"
> No other implementations add the sync marker in the metadata map, and none
> read it from there, not even the C version.
> I suggest we remove this from the header as the simplest solution.
> Another solution would be to create an AvroFileSplit class in mapred that
> knows where the blocks are, and provides the correct locations in the first
> place.
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