Github user sameeragarwal commented on a diff in the pull request: https://github.com/apache/spark/pull/14174#discussion_r71924045 --- Diff: sql/catalyst/src/main/java/org/apache/spark/sql/catalyst/expressions/RowBasedKeyValueBatch.java --- @@ -0,0 +1,182 @@ +/* + * 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.catalyst.expressions; + +import java.io.IOException; + +import org.apache.spark.memory.MemoryConsumer; +import org.apache.spark.memory.TaskMemoryManager; +import org.apache.spark.sql.types.*; +import org.apache.spark.unsafe.memory.MemoryBlock; + +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + + +/** + * RowBasedKeyValueBatch stores key value pairs in contiguous memory region. + * + * Each key or value is stored as a single UnsafeRow. Each record contains one key and one value + * and some auxiliary data, which differs based on implementation: + * i.e., `FixedLengthRowBasedKeyValueBatch` and `VariableLengthRowBasedKeyValueBatch`. + * + * We use `FixedLengthRowBasedKeyValueBatch` if all fiends in the key and the value are fixed-length + * data types. Otherwise we use `VariableLengthRowBasedKeyValueBatch`. + * + * RowBasedKeyValueBatch is backed by a single page / MemoryBlock (defaults to 64MB). If the page + * is full, the aggregate logic should fallback to a second level, larger hash map. We intentionally + * use the single-page design because it simplifies memory address encoding & decoding for each + * key-value pair. Because the maximum capacity for RowBasedKeyValueBatch is only 2^16, it is + * unlikely we need a second page anyway. Filling the page requires an average size for key value + * pairs to be larger than 1024 bytes. + * + */ +public abstract class RowBasedKeyValueBatch extends MemoryConsumer { + protected final Logger logger = LoggerFactory.getLogger(RowBasedKeyValueBatch.class); + + protected static final int DEFAULT_CAPACITY = 1 << 16; --- End diff -- This and `DEFAULT_PAGE_SIZE` can probably be private?
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