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https://issues.apache.org/jira/browse/DRILL-7064?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16812920#comment-16812920
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ASF GitHub Bot commented on DRILL-7064:
---------------------------------------
amansinha100 commented on pull request #1736: DRILL-7064: Leverage the summary
metadata for plain COUNT aggregates.
URL: https://github.com/apache/drill/pull/1736#discussion_r273298899
##########
File path:
exec/java-exec/src/main/java/org/apache/drill/exec/planner/common/CountToDirectScanUtils.java
##########
@@ -0,0 +1,110 @@
+/*
+ * 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.common;
+
+import org.apache.calcite.rel.core.AggregateCall;
+import org.apache.calcite.rel.core.Aggregate;
+import org.apache.calcite.rel.type.RelDataType;
+import org.apache.calcite.rel.type.RelDataTypeField;
+import org.apache.calcite.rel.type.RelDataTypeFieldImpl;
+import org.apache.calcite.rel.type.RelRecordType;
+import org.apache.calcite.rex.RexInputRef;
+import org.apache.calcite.rex.RexNode;
+import org.apache.calcite.sql.type.SqlTypeName;
+
+import java.util.List;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.LinkedHashMap;
+
+/**
+ * A utility class that contains helper functions used by rules that convert
COUNT(*) and COUNT(col)
+ * aggregates (no group-by) to DirectScan
+ */
+public class CountToDirectScanUtils {
+
+ /**
+ * Checks if aggregate call contains star or non-null expression:
+ * <pre>
+ * count(*) == > empty arg ==> rowCount
+ * count(Not-null-input) ==> rowCount
+ * </pre>
+ *
+ * @param aggregateCall aggregate call
+ * @param aggregate aggregate relation expression
+ * @return true of aggregate call contains star or non-null expression
+ */
+ public static boolean containsStarOrNotNullInput(AggregateCall
aggregateCall, Aggregate aggregate) {
+ return aggregateCall.getArgList().isEmpty() ||
+ (aggregateCall.getArgList().size() == 1 &&
+
!aggregate.getInput().getRowType().getFieldList().get(aggregateCall.getArgList().get(0)).getType().isNullable());
+ }
+
+ /**
+ * For each aggregate call creates field based on its name with bigint type.
+ * Constructs record type for created fields.
+ *
+ * @param aggregateRel aggregate relation expression
+ * @param fieldNames field names
+ * @return record type
+ */
+ public static RelDataType constructDataType(Aggregate aggregateRel,
Collection<String> fieldNames) {
+ List<RelDataTypeField> fields = new ArrayList<>();
+ Iterator<String> filedNamesIterator = fieldNames.iterator();
Review comment:
Done.
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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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