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https://issues.apache.org/jira/browse/DRILL-4530?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15380437#comment-15380437
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ASF GitHub Bot commented on DRILL-4530:
---------------------------------------
Github user amansinha100 commented on a diff in the pull request:
https://github.com/apache/drill/pull/519#discussion_r71059510
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/planner/logical/partition/PruneScanRule.java
---
@@ -143,6 +144,11 @@ public static final RelOptRule
getDirFilterOnScan(OptimizerRulesContext optimize
}
protected void doOnMatch(RelOptRuleCall call, Filter filterRel, Project
projectRel, TableScan scanRel) {
+ if (wasAllPartitionsPruned) {
--- End diff --
Pls see commit #ce509af for the changes. Since the 'all partitions pruned'
is a special case, I had to keep track of this state and propagate it during
the new FileSelection creation after partition pruning. Thus, if the first
phase directory pruning eliminated all partitions and we re-added 1 for schema
purposes, this directory selection will be eventually seen by the
ParquetGroupScan which will examine a flag 'wasAllPartitionsPruned' and decide
to retrieve only 1 file from this directory.
> Improve metadata cache performance for queries with single partition
> ---------------------------------------------------------------------
>
> Key: DRILL-4530
> URL: https://issues.apache.org/jira/browse/DRILL-4530
> Project: Apache Drill
> Issue Type: Improvement
> Components: Query Planning & Optimization
> Affects Versions: 1.6.0
> Reporter: Aman Sinha
> Assignee: Aman Sinha
> Fix For: Future
>
>
> Consider two types of queries which are run with Parquet metadata caching:
> {noformat}
> query 1:
> SELECT col FROM `A/B/C`;
> query 2:
> SELECT col FROM `A` WHERE dir0 = 'B' AND dir1 = 'C';
> {noformat}
> For a certain dataset, the query1 elapsed time is 1 sec whereas query2
> elapsed time is 9 sec even though both are accessing the same amount of data.
> The user expectation is that they should perform roughly the same. The main
> difference comes from reading the bigger metadata cache file at the root
> level 'A' for query2 and then applying the partitioning filter. query1 reads
> a much smaller metadata cache file at the subdirectory level.
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