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https://issues.apache.org/jira/browse/TEZ-3159?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Muhammad Samir Khan reassigned TEZ-3159:
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Assignee: Muhammad Samir Khan
> Reduce memory utilization while serializing keys and values
> -----------------------------------------------------------
>
> Key: TEZ-3159
> URL: https://issues.apache.org/jira/browse/TEZ-3159
> Project: Apache Tez
> Issue Type: Improvement
> Reporter: Rohini Palaniswamy
> Assignee: Muhammad Samir Khan
>
> Currently DataOutputBuffer is used for serializing. The underlying buffer
> keeps doubling in size when it reaches capacity. In some of the Pig scripts
> which serialize big bags, we end up with OOM in Tez as there is no space to
> double the array size. Mapreduce mode runs fine in those cases with 1G heap.
> The scenarios are
> - When combiner runs in reducer and some of the fields after combining
> are still big bags (For eg: distinct). Currently with mapreduce combiner does
> not run in reducer - MAPREDUCE-5221. Since input sort buffers hold good
> amount of memory at that time it can easily go OOM.
> - While serializing output with bags when there are multiple inputs and
> outputs and the sort buffers for those take up space.
> It is a pain especially after buffer size hits 128MB. Doubling at 128MB will
> require 128MB (existing array) +256MB (new array). Any doubling after that
> requires even more space. But most of the time the data is probably not going
> to fill up that 256MB leading to wastage.
>
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