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Posted to issues@spark.apache.org by "Michael Armbrust (JIRA)" <ji...@apache.org> on 2015/01/30 00:42:34 UTC
[jira] [Resolved] (SPARK-5309) Reduce Binary/String conversion
overhead when reading/writing Parquet files
[ https://issues.apache.org/jira/browse/SPARK-5309?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Michael Armbrust resolved SPARK-5309.
-------------------------------------
Resolution: Fixed
Fix Version/s: 1.3.0
Issue resolved by pull request 4187
[https://github.com/apache/spark/pull/4187]
> Reduce Binary/String conversion overhead when reading/writing Parquet files
> ---------------------------------------------------------------------------
>
> Key: SPARK-5309
> URL: https://issues.apache.org/jira/browse/SPARK-5309
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 1.2.0
> Reporter: MIchael Davies
> Priority: Minor
> Fix For: 1.3.0
>
>
> Converting between Parquet Binary and Java Strings can form a significant proportion of query times.
> For columns which have repeated String values (which is common) the same Binary will be repeatedly being converted.
> A simple change to cache the last converted String per column was shown to reduce query times by 25% when grouping on a data set of 66M rows on a column with many repeated Strings.
> A possible optimisation would be to hand responsibility for Binary encoding/decoding over to Parquet so that it could ensure that this was done only once per Binary value.
> Next step is to look at Parquet code and to discuss with that project, which I will do.
> More details are available on this discussion:
> http://apache-spark-developers-list.1001551.n3.nabble.com/Optimize-encoding-decoding-strings-when-using-Parquet-td10141.html
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