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https://issues.apache.org/jira/browse/PARQUET-2261?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17789168#comment-17789168
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ASF GitHub Bot commented on PARQUET-2261:
-----------------------------------------
ConeyLiu commented on code in PR #1177:
URL: https://github.com/apache/parquet-mr/pull/1177#discussion_r1403509676
##########
parquet-column/src/main/java/org/apache/parquet/column/statistics/SizeStatistics.java:
##########
@@ -0,0 +1,254 @@
+/*
+ * 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.parquet.column.statistics;
+
+import it.unimi.dsi.fastutil.longs.LongArrayList;
+import org.apache.parquet.Preconditions;
+import org.apache.parquet.io.api.Binary;
+import org.apache.parquet.schema.PrimitiveType;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Optional;
+
+/**
+ * A structure for capturing metadata for estimating the unencoded,
+ * uncompressed size of data written. This is useful for readers to estimate
+ * how much memory is needed to reconstruct data in their memory model and for
+ * fine-grained filter push down on nested structures (the histograms contained
+ * in this structure can help determine the number of nulls at a particular
+ * nesting level and maximum length of lists).
+ */
+public class SizeStatistics {
+
+ private PrimitiveType type;
+ /**
+ * The number of physical bytes stored for BYTE_ARRAY data values assuming
+ * no encoding. This is exclusive of the bytes needed to store the length of
+ * each byte array. In other words, this field is equivalent to the `(size
+ * of PLAIN-ENCODING the byte array values) - (4 bytes * number of values
+ * written)`. To determine unencoded sizes of other types readers can use
+ * schema information multiplied by the number of non-null and null values.
+ * The number of null/non-null values can be inferred from the histograms
+ * below.
+ *
+ * For example, if a column chunk is dictionary-encoded with dictionary
+ * ["a", "bc", "cde"], and a data page contains the indices [0, 0, 1, 2],
+ * then this value for that data page should be 7 (1 + 1 + 2 + 3).
+ *
+ * This field should only be set for types that use BYTE_ARRAY as their
+ * physical type.
+ */
+ private long unencodedByteArrayDataBytes;
+ /**
+ * When present, there is expected to be one element corresponding to each
+ * repetition (i.e. size=max repetition_level+1) where each element
+ * represents the number of times the repetition level was observed in the
+ * data.
+ *
+ * This field may be omitted if max_repetition_level is 0 without loss
+ * of information.
+ */
+ private List<Long> repetitionLevelHistogram;
+ /**
+ * Same as repetition_level_histogram except for definition levels.
+ *
+ * This field may be omitted if max_definition_level is 0 or 1 without
+ * loss of information.
+ */
+ private List<Long> definitionLevelHistogram;
+
+ /**
+ * Whether the statistics has valid value.
+ *
+ * It is true by default. Only set to false while it fails to merge
statistics.
+ */
+ private boolean hasValue = true;
+
+ /**
+ * Builder to create a SizeStatistics.
+ */
+ public static class Builder {
+ private PrimitiveType type;
+ private long unencodedByteArrayDataBytes;
+ private long[] repetitionLevelHistogram;
+ private long[] definitionLevelHistogram;
+
+ /**
+ * Create a builder to create a SizeStatistics.
+ *
+ * @param type physical type of the column associated with this statistics
+ * @param maxRepetitionLevel maximum repetition level of the column
+ * @param maxDefinitionLevel maximum definition level of the column
+ */
+ public Builder(PrimitiveType type, int maxRepetitionLevel, int
maxDefinitionLevel) {
+ this.type = type;
+ this.unencodedByteArrayDataBytes = 0L;
+ repetitionLevelHistogram = new long[maxRepetitionLevel + 1];
+ definitionLevelHistogram = new long[maxDefinitionLevel + 1];
+ Arrays.fill(repetitionLevelHistogram, 0L);
Review Comment:
Does this need? The array should be filled with zero by default.
> [Format] Add statistics that reflect decoded size to metadata
> -------------------------------------------------------------
>
> Key: PARQUET-2261
> URL: https://issues.apache.org/jira/browse/PARQUET-2261
> Project: Parquet
> Issue Type: New Feature
> Components: parquet-format
> Reporter: Micah Kornfield
> Assignee: Micah Kornfield
> Priority: Major
> Fix For: format-2.10.0
>
>
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