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https://issues.apache.org/jira/browse/SPARK-21657?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Ruslan Dautkhanov updated SPARK-21657:
--------------------------------------
Description:
It can take up to half a day to explode a modest-sized 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 of 50,000 (see attached pyspark script), it took 7 hours to explode
the nested collections (\!) of 8k records.
After 1000 elements in nested collection, time grows exponentially.
was:
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.
> 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-sized 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 of 50,000 (see attached pyspark script), it took 7 hours to
> explode the nested collections (\!) of 8k records.
> After 1000 elements in nested collection, time grows exponentially.
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