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From "Deron Eriksson (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SYSTEMML-906) Use of `df.first` in MLContextUtil is a Bottleneck
Date Mon, 12 Sep 2016 16:54:21 GMT

    [ https://issues.apache.org/jira/browse/SYSTEMML-906?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15484613#comment-15484613
] 

Deron Eriksson commented on SYSTEMML-906:
-----------------------------------------

An potential issue with using the schema is that if a value in a dataframe is a double but
is represented as a DataTypes.StringType, then it won't be recognized correctly.

Is there a dataframe method that can grab any row rather than the first row that doesn't cause
a bottleneck?




> Use of `df.first` in MLContextUtil is a Bottleneck
> --------------------------------------------------
>
>                 Key: SYSTEMML-906
>                 URL: https://issues.apache.org/jira/browse/SYSTEMML-906
>             Project: SystemML
>          Issue Type: Improvement
>            Reporter: Mike Dusenberry
>
> The use of {{dataframe.first()}} at {{MLContextUtil.java:497}} causes a severe bottleneck
if the input DataFrame is a lazy result of a compute-intensive chain.  We should change this
to use {{dataframe.schema}}, and then iterate over the types in the schema.
> cc [~deron]



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