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https://issues.apache.org/jira/browse/AVRO-1720?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14711019#comment-14711019
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Janosch Woschitz commented on AVRO-1720:
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Hi Niels,
I think as well it would be good to make {{hasNextBlock}} public, I was not
aware of the potential performance improvement though. I will add a separate
patch which includes this change as well.
Unfortunately just {{while (hasNext())}} is not sufficient enough since the
{{nextBlock}} method also contains the logic to skip over to next block
immediately. It just calls {{hasNext}} as sanity check.
{code}
public ByteBuffer nextBlock() throws IOException {
if (!hasNext())
throw new NoSuchElementException();
if (blockRemaining != blockCount)
throw new IllegalStateException("Not at block start.");
blockRemaining = 0; // <- skip to next block
datumIn = null;
return blockBuffer;
}
{code}
> Add an avro-tool to count records in an avro file
> -------------------------------------------------
>
> Key: AVRO-1720
> URL: https://issues.apache.org/jira/browse/AVRO-1720
> Project: Avro
> Issue Type: New Feature
> Components: java
> Reporter: Janosch Woschitz
> Priority: Minor
> Attachments: AVRO-1720.patch
>
>
> If you're dealing with bigger avro files (>100MB) it would be nice to have a
> way to quickly count the amount of records contained within that file.
> With the current state of avro-tools the only way to achieve this (to my
> current knowledge) is to dump the data to json and count the amount of
> records. For bigger files this might take a while due to the serialization
> overhead and since every record needs to be looked at.
> I added a new tool which is optimized for counting records, it does not
> serialize the records and reads only the block count for each block.
> {panel:title=Naive benchmark}
> {noformat}
> # the input file had a size of ~300MB
> $ du -sh sample.avro
> 323M sample.avro
> # using the new count tool
> $ time java -jar avro-tools.jar count sample.avro
> 331439
> real 0m4.670s
> user 0m6.167s
> sys 0m0.513s
> # the current way of counting records
> $ time java -jar avro-tools.jar tojson sample.avro | wc
> 331439 54904484 1838231743
> real 0m52.760s
> user 1m42.317s
> sys 0m3.209s
> # the overhead of wc is rather minor
> $ time java -jar avro-tools.jar tojson sample.avro > /dev/null
> real 0m47.834s
> user 0m53.317s
> sys 0m1.194s
> {noformat}
> {panel}
> This tool uses the HDFS API to handle files from any supported filesystem. I
> added the unit tests to the already existing TestDataFileTools since it
> provided convenient utility functions which I could reuse for my test
> scenarios.
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