[
https://issues.apache.org/jira/browse/SPARK-21657?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16123050#comment-16123050
]
Liang-Chi Hsieh edited comment on SPARK-21657 at 8/11/17 8:55 AM:
------------------------------------------------------------------
Maybe not very related to this issue. But I'm exploring Generate related code
to get hint about this issue. I'm curious why we still don't enable codegen of
Generate for now. [~hvanhovell] Maybe you know why it is disabled? Thanks.
was (Author: viirya):
Maybe not very related to this issue. But I'm exploring Generate related code.
I'm curious why we still don't enable codegen of Generate for now.
[~hvanhovell] Maybe you know why it is disabled? Thanks.
> Spark has exponential time complexity to explode(array of structs)
> ------------------------------------------------------------------
>
> Key: SPARK-21657
> URL: https://issues.apache.org/jira/browse/SPARK-21657
> Project: Spark
> Issue Type: Improvement
> Components: Spark Core, SQL
> Affects Versions: 2.0.0, 2.1.0, 2.1.1, 2.2.0
> Reporter: Ruslan Dautkhanov
> Labels: cache, caching, collections, nested_types, performance,
> pyspark, sparksql, sql
> Attachments: ExponentialTimeGrowth.PNG,
> nested-data-generator-and-test.py
>
>
> It can take up to half a day to explode a modest-sizes nested collection
> (0.5m).
> On a recent Xeon processors.
> See attached pyspark script that reproduces this problem.
> {code}
> cached_df = sqlc.sql('select individ, hholdid, explode(amft) from ' +
> table_name).cache()
> print sqlc.count()
> {code}
> This script generate a number of tables, with the same total number of
> records across all nested collection (see `scaling` variable in loops).
> `scaling` variable scales up how many nested elements in each record, but by
> the same factor scales down number of records in the table. So total number
> of records stays the same.
> Time grows exponentially (notice log-10 vertical axis scale):
> !ExponentialTimeGrowth.PNG!
> At scaling 50,000 it took 7 hours to explode the nested collections (\!) of
> 8k records.
> After 1000 elements in nested collection, time grows exponentially.
--
This message was sent by Atlassian JIRA
(v6.4.14#64029)
---------------------------------------------------------------------
To unsubscribe, e-mail: issues-unsubscr...@spark.apache.org
For additional commands, e-mail: issues-h...@spark.apache.org
