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ConvertCountToDirectScanRule.java
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ConvertCountToDirectScanRule.java
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/*
* 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.physical.impl.statistics.Statistic;
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");
public static final RelOptRule AGG_ON_SCAN = new ConvertCountToDirectScanRule(
RelOptHelper.some(Aggregate.class,
RelOptHelper.any(TableScan.class)), "Agg_on_scan");
private static final org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(ConvertCountToDirectScanRule.class);
protected ConvertCountToDirectScanRule(RelOptRuleOperand rule, String id) {
super(rule, "ConvertCountToDirectScanRule:" + id);
}
@Override
public void onMatch(RelOptRuleCall call) {
final Aggregate agg = (Aggregate) call.rel(0);
final TableScan scan = (TableScan) call.rel(call.rels.length - 1);
final Project project = call.rels.length == 3 ? (Project) call.rel(1) : null;
// Qualifying conditions for rule:
// 1) There's no GroupBY key,
// 2) Agg is not a DISTINCT agg
// 3) Additional checks are done further below ..
if (agg.getGroupCount() > 0 ||
agg.containsDistinctCall()) {
return;
}
DrillTable drillTable = DrillRelOptUtil.getDrillTable(scan);
if (drillTable == null) {
logger.debug("Rule does not apply since an eligible drill table instance was not found.");
return;
}
Object selection = drillTable.getSelection();
if (!(selection instanceof FormatSelection)) {
logger.debug("Rule does not apply since only Parquet file format is eligible.");
return;
}
PlannerSettings settings = call.getPlanner().getContext().unwrap(PlannerSettings.class);
// Rule is applicable only if the statistics for row count and null count are available from the metadata,
FormatSelection formatSelection = (FormatSelection) selection;
// Rule cannot be applied if the selection had wildcard since the totalrowcount cannot be read from the parent directory
if (formatSelection.getSelection().hadWildcard()) {
logger.debug("Rule does not apply when there is a wild card since the COUNT could not be determined from metadata.");
return;
}
Pair<Boolean, Metadata_V4.MetadataSummary> status = checkMetadataForScanStats(settings, drillTable, formatSelection);
if (!status.getLeft()) {
logger.debug("Rule does not apply since MetadataSummary metadata was not found.");
return;
}
Metadata_V4.MetadataSummary metadataSummary = status.getRight();
Map<String, Long> result = collectCounts(settings, metadataSummary, agg, scan, project);
logger.trace("Calculated the following aggregate counts: ", result);
// if counts could not be determined, rule won't be applied
if (result.isEmpty()) {
logger.debug("Rule does not apply since one or more COUNTs could not be determined from metadata.");
return;
}
List<Path> fileList =
ImmutableList.of(Metadata.getSummaryFileName(formatSelection.getSelection().getSelectionRoot()));
final RelDataType scanRowType = CountToDirectScanUtils.constructDataType(agg, result.keySet());
final DynamicPojoRecordReader<Long> reader = new DynamicPojoRecordReader<>(
CountToDirectScanUtils.buildSchema(scanRowType.getFieldNames()),
Collections.singletonList((List<Long>) new ArrayList<>(result.values())));
final ScanStats scanStats = new ScanStats(ScanStats.GroupScanProperty.EXACT_ROW_COUNT, 1, 1, scanRowType.getFieldCount());
final MetadataDirectGroupScan directScan = new MetadataDirectGroupScan(reader, fileList, scanStats, true);
final DrillDirectScanRel newScan = new DrillDirectScanRel(scan.getCluster(), scan.getTraitSet().plus(DrillRel.DRILL_LOGICAL),
directScan, scanRowType);
final DrillProjectRel newProject = new DrillProjectRel(agg.getCluster(), agg.getTraitSet().plus(DrillRel.DRILL_LOGICAL),
newScan, CountToDirectScanUtils.prepareFieldExpressions(scanRowType), agg.getRowType());
call.transformTo(newProject);
}
private Pair<Boolean, Metadata_V4.MetadataSummary> checkMetadataForScanStats(PlannerSettings settings, DrillTable drillTable,
FormatSelection formatSelection) {
// Currently only support metadata rowcount stats for Parquet tables
FormatPluginConfig formatConfig = formatSelection.getFormat();
if (!((formatConfig instanceof ParquetFormatConfig)
|| ((formatConfig instanceof NamedFormatPluginConfig)
&& ((NamedFormatPluginConfig) formatConfig).name.equals("parquet")))) {
return new ImmutablePair<Boolean, Metadata_V4.MetadataSummary>(false, null);
}
FileSystemPlugin plugin = (FileSystemPlugin) drillTable.getPlugin();
DrillFileSystem fs = null;
try {
fs = new DrillFileSystem(plugin.getFormatPlugin(formatSelection.getFormat()).getFsConf());
} catch (IOException e) {
logger.warn("Unable to create the file system object for retrieving statistics from metadata cache file ", e);
return new ImmutablePair<Boolean, Metadata_V4.MetadataSummary>(false, null);
}
// check if the cacheFileRoot has been set: this is needed because after directory pruning, the
// cacheFileRoot could have been changed and not be the same as the original selectionRoot
Path selectionRoot = formatSelection.getSelection().getCacheFileRoot() != null ?
formatSelection.getSelection().getCacheFileRoot() :
formatSelection.getSelection().getSelectionRoot();
ParquetReaderConfig parquetReaderConfig= ParquetReaderConfig.builder()
.withFormatConfig((ParquetFormatConfig) formatConfig)
.withOptions(settings.getOptions())
.build();
Metadata_V4.MetadataSummary metadataSummary = Metadata.getSummary(fs, selectionRoot, false, parquetReaderConfig);
return metadataSummary != null ? new ImmutablePair<Boolean, Metadata_V4.MetadataSummary>(true, metadataSummary) :
new ImmutablePair<Boolean, Metadata_V4.MetadataSummary>(false, null);
}
/**
* Collects counts for each aggregation call by using the metadata summary information
* Will return empty result map if was not able to determine count for at least one aggregation call.
*
* For each aggregate call will determine if count can be calculated. Collects counts only for COUNT function.
* 1. First, we get the total row count from the metadata summary.
* 2. For COUNT(*) and COUNT(<non null column>) and COUNT(<implicit column>), the count = total row count
* 3. For COUNT(nullable column), count = (total row count - column's null count)
* 4. Also count can not be calculated for parition columns.
*
* @param settings planner options
* @param metadataSummary metadata summary containing row counts and column counts
* @param agg aggregate relational expression
* @param scan scan relational expression
* @param project project relational expression
* @return result map where key is count column name, value is count value
*/
private Map<String, Long> collectCounts(PlannerSettings settings, Metadata_V4.MetadataSummary metadataSummary,
Aggregate agg, TableScan scan, Project project) {
final Set<String> implicitColumnsNames = ColumnExplorer.initImplicitFileColumns(settings.getOptions()).keySet();
final long totalRecordCount = metadataSummary.getTotalRowCount();
final LinkedHashMap<String, Long> result = new LinkedHashMap<>();
for (int i = 0; i < agg.getAggCallList().size(); i++) {
AggregateCall aggCall = agg.getAggCallList().get(i);
long cnt;
// rule can be applied only for count function, return empty counts
if (!"count".equalsIgnoreCase(aggCall.getAggregation().getName()) ) {
return ImmutableMap.of();
}
if (CountToDirectScanUtils.containsStarOrNotNullInput(aggCall, agg)) {
cnt = totalRecordCount;
} else if (aggCall.getArgList().size() == 1) {
// count(columnName) ==> Agg ( Scan )) ==> columnValueCount
int index = aggCall.getArgList().get(0);
if (project != null) {
// project in the middle of Agg and Scan : Only when input of AggCall is a RexInputRef in Project, we find the index of Scan's field.
// For instance,
// Agg - count($0)
// \
// Proj - Exp={$1}
// \
// Scan (col1, col2).
// return count of "col2" in Scan's metadata, if found.
if (!(project.getProjects().get(index) instanceof RexInputRef)) {
return ImmutableMap.of(); // do not apply for all other cases.
}
index = ((RexInputRef) project.getProjects().get(index)).getIndex();
}
String columnName = scan.getRowType().getFieldNames().get(index).toLowerCase();
// for implicit column count will be the same as total record count
if (implicitColumnsNames.contains(columnName)) {
cnt = totalRecordCount;
} else {
SchemaPath simplePath = SchemaPath.getSimplePath(columnName);
if (ColumnExplorer.isPartitionColumn(settings.getOptions(), simplePath)) {
return ImmutableMap.of();
}
Metadata_V4.ColumnTypeMetadata_v4 columnMetadata = metadataSummary.getColumnTypeInfo(new Metadata_V4.ColumnTypeMetadata_v4.Key(simplePath));
if (columnMetadata == null || columnMetadata.totalNullCount == Statistic.NO_COLUMN_STATS) {
// if column stats is not available don't apply this rule, return empty counts
return ImmutableMap.of();
} else {
// count of a nullable column = (total row count - column's null count)
cnt = totalRecordCount - columnMetadata.totalNullCount;
}
}
} else {
return ImmutableMap.of();
}
String name = "count" + i + "$" + (aggCall.getName() == null ? aggCall.toString() : aggCall.getName());
result.put(name, cnt);
}
return ImmutableMap.copyOf(result);
}
}