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https://issues.apache.org/jira/browse/SPARK-5511?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15554357#comment-15554357
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Xiao Li commented on SPARK-5511:
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This requires the changes on Parquet.
> [SQL] Possible optimisations for predicate pushdowns from Spark SQL to Parquet
> ------------------------------------------------------------------------------
>
> Key: SPARK-5511
> URL: https://issues.apache.org/jira/browse/SPARK-5511
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 1.2.0
> Reporter: Mick Davies
> Priority: Minor
>
> The following changes could make predicate pushdown more effective under
> certain conditions, which are not uncommon.
> 1. Parquet predicate evaluation does not use dictionary compression
> information, furthermore it circumvents dictionary decoding optimisations
> (https://issues.apache.org/jira/browse/PARQUET-36). This means predicates are
> re-evaluated repeatedly for the same Strings, and also Binary->String
> conversions are repeated. This is a change purely on the Parquet side.
> 2. Support IN clauses in predicate pushdown. This requires changes to Parquet
> and then subsequently in Spark SQL.
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