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https://issues.apache.org/jira/browse/DRILL-7763?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17216274#comment-17216274
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ASF GitHub Bot commented on DRILL-7763:
---------------------------------------
vvysotskyi commented on a change in pull request #2092:
URL: https://github.com/apache/drill/pull/2092#discussion_r507174594
##########
File path:
exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/AbstractGroupScanWithMetadata.java
##########
@@ -454,26 +454,40 @@ public boolean supportsLimitPushdown() {
return true;
}
+ public void setLimit (int limitToPushDown) {
+ this.maxRecords = limitToPushDown;
+ }
+
@Override
public GroupScan applyLimit(int maxRecords) {
- this.maxRecords = maxRecords;
- this.maxRecords = Math.max(this.maxRecords, 1); // Make sure it request at
least 1 row -> 1 file.
+ maxRecords = Math.max(maxRecords, 1); // Make sure it request at least 1
row -> 1 file.
GroupScanWithMetadataFilterer<?> prunedMetadata = getFilterer();
if (getTableMetadata() != null) {
long tableRowCount =
TableStatisticsKind.ROW_COUNT.getValue(getTableMetadata());
- if (tableRowCount == Statistic.NO_COLUMN_STATS || tableRowCount <=
this.maxRecords) {
+ if (tableRowCount == Statistic.NO_COLUMN_STATS || tableRowCount <=
maxRecords) {
logger.debug("limit push down does not apply, since total number of
rows [{}] is less or equal to the required [{}].",
tableRowCount, maxRecords);
+ // Return the group scan with the limit pushed down
+ if (this.maxRecords != maxRecords) {
+ this.setLimit(maxRecords);
Review comment:
This line modifies this instance of a group scan. Please create a new
instance using a copy constructor, set the value there, and return it.
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> Add Limit Pushdown to File Based Storage Plugins
> ------------------------------------------------
>
> Key: DRILL-7763
> URL: https://issues.apache.org/jira/browse/DRILL-7763
> Project: Apache Drill
> Issue Type: Improvement
> Affects Versions: 1.17.0
> Reporter: Charles Givre
> Assignee: Charles Givre
> Priority: Major
> Fix For: 1.19.0
>
>
> As currently implemented, when querying a file, Drill will read the entire
> file even if a limit is specified in the query. This PR does a few things:
> # Refactors the EasyGroupScan, EasySubScan, and EasyFormatConfig to allow
> the option of pushing down limits.
> # Applies this to all the EVF based format plugins which are: LogRegex,
> PCAP, SPSS, Esri, Excel and Text (CSV).
> Due to JSON's fluid schema, it would be unwise to adopt the limit pushdown as
> it could result in very inconsistent schemata.
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