c21 commented on a change in pull request #34298:
URL: https://github.com/apache/spark/pull/34298#discussion_r738654047
##########
File path:
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/orc/OrcUtils.scala
##########
@@ -377,4 +381,116 @@ object OrcUtils extends Logging {
case _ => false
}
}
+
+ /**
+ * When the partial aggregates (Max/Min/Count) are pushed down to ORC, we
don't need to read data
+ * from ORC and aggregate at Spark layer. Instead we want to get the partial
aggregates
+ * (Max/Min/Count) result using the statistics information from ORC file
footer, and then
+ * construct an InternalRow from these aggregate results.
+ *
+ * @return Aggregate results in the format of InternalRow
+ */
+ def createAggInternalRowFromFooter(
+ reader: Reader,
+ filePath: String,
+ dataSchema: StructType,
+ partitionSchema: StructType,
+ aggregation: Aggregation,
+ aggSchema: StructType): InternalRow = {
+ require(aggregation.groupByColumns.length == 0,
+ s"aggregate $aggregation with group-by column shouldn't be pushed down")
+ var columnsStatistics: OrcColumnStatistics = null
+ try {
+ columnsStatistics = OrcFooterReader.readStatistics(reader)
+ } catch { case e: RuntimeException =>
+ throw new SparkException(
+ s"Cannot read columns statistics in file: $filePath. Please consider
disabling " +
+ s"ORC aggregate push down by setting 'spark.sql.orc.aggregatePushdown'
to false.", e)
+ }
Review comment:
I think the only case is the statistics is missing and
`OrcFooterReader.convertStatistics():orcStatistics.remove()` throws
`RuntimeException`. But just to be safe, I changed to match all `Exception`
here.
##########
File path:
sql/core/src/main/java/org/apache/spark/sql/execution/datasources/orc/OrcColumnStatistics.java
##########
@@ -0,0 +1,80 @@
+/*
+ * 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.spark.sql.execution.datasources.orc;
+
+import org.apache.orc.ColumnStatistics;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Columns statistics interface wrapping ORC {@link ColumnStatistics}s.
+ *
+ * Because ORC {@link ColumnStatistics}s are stored as an flatten array in ORC
file footer,
+ * this class is used to covert ORC {@link ColumnStatistics}s from array to
nested tree structure,
+ * according to data types. The flatten array stores all data types (including
nested types) in
+ * tree pre-ordering. This is used for aggregate push down in ORC.
+ *
+ * For nested data types (array, map and struct), the sub-field statistics are
stored recursively
+ * inside parent column's `children` field. Here is an example of
`OrcColumnStatistics`:
Review comment:
@huaxingao - thanks, updated for all class-level comments. For method
comments or comments in method's body, the {@code} does not work, so not
changed. There are also back quotes used in comments in our code base as well
for comments in body of method.
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