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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-5516) Limit memory usage for Hbase reader
Date Thu, 18 May 2017 17:11:04 GMT

    [ https://issues.apache.org/jira/browse/DRILL-5516?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16016099#comment-16016099

ASF GitHub Bot commented on DRILL-5516:

Github user sudheeshkatkam commented on the issue:


> Limit memory usage for Hbase reader
> -----------------------------------
>                 Key: DRILL-5516
>                 URL: https://issues.apache.org/jira/browse/DRILL-5516
>             Project: Apache Drill
>          Issue Type: Improvement
>          Components: Storage - HBase
>    Affects Versions: 1.10.0
>            Reporter: Arina Ielchiieva
>            Assignee: Arina Ielchiieva
>             Fix For: 1.11.0
> If early limit 0 optimization is set to true (alter session set `planner.enable_limit0_optimization`
= true), when executing limit 0 queries Drill will return data type from available metadata
if possible.
> When Drill can not determine data types from metadata (or if early limit 0 optimization
is set to false), Drill will read first batch of data and determine schema.
> Hbase reader determines max batch size using magic number (4000) which can lead to OOM
when row size is large. The overall vector/batch size issue will be reconsidered in future
releases.This is temporary fix to avoid OOM.
> To limit memory usage for Hbase reader we are adding max allowed allocated memory contant
which will default to 64 mb. Thus batch size will be limited to 4000 (as before if memory
limit does not exceed) or to number of records that are within max allowed memory limit. If
first row in batch is larger than allowed default, it will be written in batch but batch will
contain only this row.

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