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https://issues.apache.org/jira/browse/DRILL-2568?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14381248#comment-14381248
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Jacques Nadeau commented on DRILL-2568:
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Can you please post review board?
> New partition pruning prevents the optimization for trivial COUNT(*) queries
> ----------------------------------------------------------------------------
>
> Key: DRILL-2568
> URL: https://issues.apache.org/jira/browse/DRILL-2568
> Project: Apache Drill
> Issue Type: Bug
> Components: Query Planning & Optimization
> Affects Versions: 0.8.0
> Reporter: Aman Sinha
> Assignee: Aman Sinha
> Attachments:
> 0001-DRILL-2568-Drop-filter-plan-node-if-all-conjuncts-ha.patch
>
>
> With the new interpreter based partition pruning, if the query has only
> partition filters and they are pushed into the Scan, we don't drop the Filter
> node from the plan. This prevents the optimization for COUNT(*) queries
> against parquet files where we read the count values directly from the
> parquet files instead of scanning and aggregating. The
> ConvertCountToDirectScan rule does not get applied if there is an intervening
> Filter between the Scan and the Aggregate nodes.
> {code}
> 0: jdbc:drill:zk=local> explain plan for select count(*) from
> dfs.`/Users/asinha/data/multilevel/parquet` where dir0=1995;
> +------------+------------+
> | text | json |
> +------------+------------+
> | 00-00 Screen
> 00-01 StreamAgg(group=[{}], EXPR$0=[COUNT()])
> 00-02 Project($f0=[0])
> 00-03 SelectionVectorRemover
> 00-04 Filter(condition=[=($0, 1995)])
> 00-05 Scan(groupscan=[ParquetGroupScan
> [entries=[ReadEntryWithPath
> [path=file:/Users/asinha/data/multilevel/parquet/1995/Q1/orders_95_q1.parquet],
> ReadEntryWithPath
> [path=file:/Users/asinha/data/multilevel/parquet/1995/Q2/orders_95_q2.parquet],
> ReadEntryWithPath
> [path=file:/Users/asinha/data/multilevel/parquet/1995/Q3/orders_95_q3.parquet],
> ReadEntryWithPath
> [path=file:/Users/asinha/data/multilevel/parquet/1995/Q4/orders_95_q4.parquet]],
> selectionRoot=/Users/asinha/data/multilevel/parquet, numFiles=4,
> columns=[`dir0`]]])
> {code}
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