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https://issues.apache.org/jira/browse/DRILL-6115?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16360107#comment-16360107
]
ASF GitHub Bot commented on DRILL-6115:
---------------------------------------
Github user amansinha100 commented on a diff in the pull request:
https://github.com/apache/drill/pull/1110#discussion_r167447232
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/planner/physical/visitor/InsertLocalExchangeVisitor.java
---
@@ -20,133 +20,34 @@
import com.google.common.collect.Lists;
import org.apache.drill.exec.planner.physical.ExchangePrel;
-import org.apache.drill.exec.planner.physical.HashPrelUtil;
-import
org.apache.drill.exec.planner.physical.HashPrelUtil.HashExpressionCreatorHelper;
-import org.apache.drill.exec.planner.physical.HashToRandomExchangePrel;
import org.apache.drill.exec.planner.physical.PlannerSettings;
import org.apache.drill.exec.planner.physical.Prel;
-import org.apache.drill.exec.planner.physical.ProjectPrel;
-import
org.apache.drill.exec.planner.physical.DrillDistributionTrait.DistributionField;
-import org.apache.drill.exec.planner.physical.UnorderedDeMuxExchangePrel;
-import org.apache.drill.exec.planner.physical.UnorderedMuxExchangePrel;
-import org.apache.drill.exec.planner.sql.DrillSqlOperator;
import org.apache.drill.exec.server.options.OptionManager;
import org.apache.calcite.rel.RelNode;
-import org.apache.calcite.rel.type.RelDataType;
-import org.apache.calcite.rel.type.RelDataTypeField;
-import org.apache.calcite.rex.RexBuilder;
-import org.apache.calcite.rex.RexNode;
-import org.apache.calcite.rex.RexUtil;
-
-import java.math.BigDecimal;
-import java.util.Collections;
import java.util.List;
public class InsertLocalExchangeVisitor extends BasePrelVisitor<Prel,
Void, RuntimeException> {
- private final boolean isMuxEnabled;
- private final boolean isDeMuxEnabled;
-
-
- public static class RexNodeBasedHashExpressionCreatorHelper implements
HashExpressionCreatorHelper<RexNode> {
- private final RexBuilder rexBuilder;
-
- public RexNodeBasedHashExpressionCreatorHelper(RexBuilder rexBuilder) {
- this.rexBuilder = rexBuilder;
- }
-
- @Override
- public RexNode createCall(String funcName, List<RexNode> inputFields) {
- final DrillSqlOperator op =
- new DrillSqlOperator(funcName, inputFields.size(), true, false);
- return rexBuilder.makeCall(op, inputFields);
- }
- }
+ private final OptionManager options;
public static Prel insertLocalExchanges(Prel prel, OptionManager
options) {
boolean isMuxEnabled =
options.getOption(PlannerSettings.MUX_EXCHANGE.getOptionName()).bool_val;
boolean isDeMuxEnabled =
options.getOption(PlannerSettings.DEMUX_EXCHANGE.getOptionName()).bool_val;
if (isMuxEnabled || isDeMuxEnabled) {
- return prel.accept(new InsertLocalExchangeVisitor(isMuxEnabled,
isDeMuxEnabled), null);
+ return prel.accept(new InsertLocalExchangeVisitor(options), null);
--- End diff --
Since the local variables isMuxEnabled/disabled are not being used anymore,
you can remove them on lines 33, 34.
> SingleMergeExchange is not scaling up when many minor fragments are allocated
> for a query.
> ------------------------------------------------------------------------------------------
>
> Key: DRILL-6115
> URL: https://issues.apache.org/jira/browse/DRILL-6115
> Project: Apache Drill
> Issue Type: Improvement
> Components: Execution - Relational Operators
> Affects Versions: 1.12.0
> Reporter: Hanumath Rao Maduri
> Assignee: Hanumath Rao Maduri
> Priority: Major
> Fix For: 1.13.0
>
> Attachments: Enhancing Drill to multiplex ordered merge exchanges.docx
>
>
> SingleMergeExchange is created when a global order is required in the output.
> The following query produces the SingleMergeExchange.
> {code:java}
> 0: jdbc:drill:zk=local> explain plan for select L_LINENUMBER from
> dfs.`/drill/tables/lineitem` order by L_LINENUMBER;
> +------+------+
> | text | json |
> +------+------+
> | 00-00 Screen
> 00-01 Project(L_LINENUMBER=[$0])
> 00-02 SingleMergeExchange(sort0=[0])
> 01-01 SelectionVectorRemover
> 01-02 Sort(sort0=[$0], dir0=[ASC])
> 01-03 HashToRandomExchange(dist0=[[$0]])
> 02-01 Scan(table=[[dfs, /drill/tables/lineitem]],
> groupscan=[JsonTableGroupScan [ScanSpec=JsonScanSpec
> [tableName=maprfs:///drill/tables/lineitem, condition=null],
> columns=[`L_LINENUMBER`], maxwidth=15]])
> {code}
> On a 10 node cluster if the table is huge then DRILL can spawn many minor
> fragments which are all merged on a single node with one merge receiver.
> Doing so will create lot of memory pressure on the receiver node and also
> execution bottleneck. To address this issue, merge receiver should be
> multiphase merge receiver.
> Ideally for large cluster one can introduce tree merges so that merging can
> be done parallel. But as a first step I think it is better to use the
> existing infrastructure for multiplexing operators to generate an OrderedMux
> so that all the minor fragments pertaining to one DRILLBIT should be merged
> and the merged data can be sent across to the receiver operator.
> On a 10 node cluster if each node processes 14 minor fragments.
> Current version of code merges 140 minor fragments
> the proposed version has two level merges 1 - 14 merge in each drillbit which
> is parallel
> and 10 minorfragments are merged at the receiver node.
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