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https://issues.apache.org/jira/browse/DRILL-4530?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15373772#comment-15373772
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ASF GitHub Bot commented on DRILL-4530:
---------------------------------------
Github user jinfengni commented on a diff in the pull request:
https://github.com/apache/drill/pull/519#discussion_r70529269
--- 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 --
I feel this flag may lead to scenarios where pruning does not happen when
it should. The flag is PruneScanRule's internal variable. The same rule could
be applied to pruning for multiple tables. So, if PruneScanRule turns on this
flag for T1, then we might skip pruning logic for T2 later on, when this rule
is fired.
> 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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