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https://issues.apache.org/jira/browse/DRILL-7064?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16811825#comment-16811825
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ASF GitHub Bot commented on DRILL-7064:
---------------------------------------
vvysotskyi commented on pull request #1736: DRILL-7064: Leverage the summary
metadata for plain COUNT aggregates.
URL: https://github.com/apache/drill/pull/1736#discussion_r272827208
##########
File path:
exec/java-exec/src/main/java/org/apache/drill/exec/planner/logical/ConvertCountToDirectScanRule.java
##########
@@ -0,0 +1,296 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.drill.exec.planner.logical;
+
+import org.apache.calcite.plan.RelOptRule;
+import org.apache.calcite.plan.RelOptRuleCall;
+import org.apache.calcite.plan.RelOptRuleOperand;
+import org.apache.calcite.rel.core.Aggregate;
+import org.apache.calcite.rel.core.AggregateCall;
+import org.apache.calcite.rel.core.Project;
+import org.apache.calcite.rel.core.TableScan;
+import org.apache.calcite.rel.type.RelDataType;
+import org.apache.calcite.rex.RexInputRef;
+import org.apache.commons.lang3.tuple.ImmutablePair;
+import org.apache.commons.lang3.tuple.Pair;
+import org.apache.drill.common.expression.SchemaPath;
+import org.apache.drill.common.logical.FormatPluginConfig;
+
+import org.apache.drill.exec.physical.base.ScanStats;
+import org.apache.drill.exec.planner.common.CountToDirectScanUtils;
+import org.apache.drill.exec.planner.common.DrillRelOptUtil;
+
+import org.apache.drill.exec.planner.physical.PlannerSettings;
+import org.apache.drill.exec.store.ColumnExplorer;
+import org.apache.drill.exec.store.dfs.DrillFileSystem;
+import org.apache.drill.exec.store.dfs.FileSystemPlugin;
+import org.apache.drill.exec.store.dfs.FormatSelection;
+import org.apache.drill.exec.store.dfs.NamedFormatPluginConfig;
+import org.apache.drill.exec.store.direct.MetadataDirectGroupScan;
+import org.apache.drill.exec.store.parquet.ParquetFormatConfig;
+import org.apache.drill.exec.store.parquet.ParquetReaderConfig;
+import org.apache.drill.exec.store.parquet.metadata.Metadata;
+import org.apache.drill.exec.store.parquet.metadata.Metadata_V4;
+import org.apache.drill.exec.store.pojo.DynamicPojoRecordReader;
+import org.apache.drill.shaded.guava.com.google.common.collect.ImmutableList;
+import org.apache.drill.shaded.guava.com.google.common.collect.ImmutableMap;
+import org.apache.hadoop.fs.Path;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.LinkedHashMap;
+import java.util.Set;
+
+/**
+ * <p> This rule is a logical planning counterpart to a corresponding
<b>ConvertCountToDirectScanPrule</b>
+ * physical rule
+ * </p>
+ * <p>
+ * This rule will convert <b>" select count(*) as mycount from table "</b>
+ * or <b>" select count(not-nullable-expr) as mycount from table "</b> into
+ * <pre>
+ * Project(mycount)
+ * \
+ * DirectGroupScan ( PojoRecordReader ( rowCount ))
+ *</pre>
+ * or <b>" select count(column) as mycount from table "</b> into
+ * <pre>
+ * Project(mycount)
+ * \
+ * DirectGroupScan (PojoRecordReader (columnValueCount))
+ *</pre>
+ * Rule can be applied if query contains multiple count expressions.
+ * <b>" select count(column1), count(column2), count(*) from table "</b>
+ * </p>
+ *
+ * <p>
+ * The rule utilizes the Parquet Metadata Cache's summary information to
retrieve the total row count
+ * and the per-column null count. As such, the rule is only applicable for
Parquet tables and only if the
+ * metadata cache has been created with the summary information.
+ * </p>
+ */
+public class ConvertCountToDirectScanRule extends RelOptRule {
+
+ public static final RelOptRule AGG_ON_PROJ_ON_SCAN = new
ConvertCountToDirectScanRule(
+ RelOptHelper.some(Aggregate.class,
+ RelOptHelper.some(Project.class,
+ RelOptHelper.any(TableScan.class))),
"Agg_on_proj_on_scan:logical");
+
+ public static final RelOptRule AGG_ON_SCAN = new
ConvertCountToDirectScanRule(
+ RelOptHelper.some(Aggregate.class,
+ RelOptHelper.any(TableScan.class)),
"Agg_on_scan:logical");
Review comment:
And here also.
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> Leverage the summary's totalRowCount and totalNullCount for COUNT() queries
> (also prevent eager expansion of files)
> -------------------------------------------------------------------------------------------------------------------
>
> Key: DRILL-7064
> URL: https://issues.apache.org/jira/browse/DRILL-7064
> Project: Apache Drill
> Issue Type: Sub-task
> Components: Metadata
> Reporter: Venkata Jyothsna Donapati
> Assignee: Aman Sinha
> Priority: Major
> Fix For: 1.16.0
>
> Original Estimate: 336h
> Remaining Estimate: 336h
>
> This sub-task is meant to leverage the Parquet metadata cache's summary
> stats: totalRowCount (across all files and row groups) and the per-column
> totalNullCount (across all files and row groups) to answer plain COUNT
> aggregation queries without Group-By. These are currently converted to a
> DirectScan by the ConvertCountToDirectScanRule which utilizes the row group
> metadata; however this rule is applied on Drill Logical rels and converts the
> logical plan to a physical plan with DirectScanPrel but this is too late
> since the DrillScanRel that is already created during logical planning has
> already read the entire metadata cache file along with its full list of row
> group entries. The metadata cache file can grow quite large and this does not
> scale.
> The solution is to use the Metadata Summary file that is created in
> DRILL-7063 and create a new rule that will apply early on such that it
> operates on the Calcite logical rels instead of the Drill logical rels and
> prevents eager expansion of the list of files/row groups.
> We will not remove the existing rule. The existing rule will continue to
> operate as before because it is possible that after some transformations, we
> still want to apply the optimizations for COUNT queries.
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