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GH-2870: Report compressed dictionary page sizes in the CLI #3798

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3f1261c
GH-2870: Report compressed dictionary page sizes in the CLI
1fanwang Sep 18, 2026
1b369bb
GH-2870: Include unused dictionaries in page size summaries
1fanwang Sep 18, 2026
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8 changes: 2 additions & 6 deletions parquet-cli/src/main/java/org/apache/parquet/cli/commands/ShowPagesCommand.java
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Original file line number Diff line number Diff line change
Expand Up @@ -206,9 +206,7 @@ private long getPageCompressedSize() {
reader.getFileMetaData().getSchema().getColumns().indexOf(currentColumn);
ColumnChunkMetaData columnChunk = rowGroup.getColumns().get(columnIndex);

long startOffset = columnChunk.hasDictionaryPage()
? columnChunk.getDictionaryPageOffset()
: columnChunk.getFirstDataPageOffset();
long startOffset = columnChunk.getStartingPos();
input.seek(startOffset);
long endPos = startOffset + columnChunk.getTotalSize();
int currentPageIndex = 0;
Expand All @@ -229,9 +227,7 @@ private long getPageCompressedSize() {
}

private String printDictionaryPage(DictionaryPage dict) {
// TODO: the compressed size of a dictionary page is lost in Parquet
dict.getUncompressedSize();
long totalSize = dict.getCompressedSize();
long totalSize = getPageCompressedSize();

@divjotarora divjotarora Sep 18, 2026

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getPageCompressedSize calls columnChunk.hasDictionaryPage() to determine the page offset. This function does:

  public boolean hasDictionaryPage() {
    EncodingStats stats = getEncodingStats();
    if (stats != null) {
      // ensure there is a dictionary page and that it is used to encode data pages
      return stats.hasDictionaryPages() && stats.hasDictionaryEncodedPages();
    }

    Set<Encoding> encodings = getEncodings();
    return (encodings.contains(PLAIN_DICTIONARY) || encodings.contains(RLE_DICTIONARY));
  }

In an edge case where a writer emits a dictionary page followed by no PLAIN_DICTIONARY or RLE_DICTIONARY data pages, we would get wrong results because hasDictionaryPage() returns false.

Realistically, writers wouldn't do this, but I didn't find any wording in the spec explicitly disallowing it. The TestParquetFileWriter code in this repo seems to do exactly this.

int count = dict.getDictionarySize();
float perValue = ((float) totalSize) / count;
String enc = encodingAsString(dict.getEncoding(), true);
Expand Down
177 changes: 177 additions & 0 deletions parquet-cli/src/test/java/org/apache/parquet/cli/commands/ShowPagesCommandTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -18,13 +18,47 @@
*/
package org.apache.parquet.cli.commands;

import static org.apache.parquet.cli.Util.humanReadable;
import static org.apache.parquet.column.Encoding.PLAIN;
import static org.apache.parquet.column.Encoding.RLE;
import static org.apache.parquet.schema.PrimitiveType.PrimitiveTypeName.BINARY;
import static org.apache.parquet.schema.PrimitiveType.PrimitiveTypeName.INT32;
import static org.assertj.core.api.Assertions.assertThat;

import java.io.File;
import java.io.IOException;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.parquet.bytes.BytesInput;
import org.apache.parquet.column.ParquetProperties.WriterVersion;
import org.apache.parquet.column.page.DictionaryPage;
import org.apache.parquet.column.statistics.Statistics;
import org.apache.parquet.example.data.Group;
import org.apache.parquet.example.data.simple.SimpleGroupFactory;
import org.apache.parquet.format.PageHeader;
import org.apache.parquet.format.PageType;
import org.apache.parquet.format.Util;
import org.apache.parquet.hadoop.ParquetFileReader;
import org.apache.parquet.hadoop.ParquetFileWriter;
import org.apache.parquet.hadoop.ParquetReader;
import org.apache.parquet.hadoop.ParquetWriter;
import org.apache.parquet.hadoop.example.ExampleParquetWriter;
import org.apache.parquet.hadoop.example.GroupReadSupport;
import org.apache.parquet.hadoop.metadata.ColumnChunkMetaData;
import org.apache.parquet.hadoop.metadata.CompressionCodecName;
import org.apache.parquet.hadoop.util.HadoopInputFile;
import org.apache.parquet.hadoop.util.HadoopOutputFile;
import org.apache.parquet.io.SeekableInputStream;
import org.apache.parquet.schema.MessageType;
import org.apache.parquet.schema.PrimitiveType;
import org.apache.parquet.schema.Types;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.CsvSource;
import org.slf4j.event.LoggingEvent;

public class ShowPagesCommandTest extends ParquetFileTest {
@Test
Expand All @@ -35,4 +69,147 @@ public void testShowPagesCommand() throws IOException {
command.setConf(new Configuration());
assertThat(command.run()).isZero();
}

@Test
public void testUnusedDictionaryPageSizes() throws IOException {
Path path = new Path(randomParquetFile().toURI());
Configuration conf = new Configuration();
PrimitiveType type = Types.required(INT32).named("value");
MessageType schema = new MessageType("record", type);
try (ParquetFileWriter writer = new ParquetFileWriter(
HadoopOutputFile.fromPath(path, conf),
schema,
ParquetFileWriter.Mode.CREATE,
ParquetWriter.DEFAULT_BLOCK_SIZE,
ParquetWriter.MAX_PADDING_SIZE_DEFAULT)) {
writer.start();
writer.startBlock(2);
writer.startColumn(
schema.getColumnDescription(new String[] {"value"}), 2, CompressionCodecName.UNCOMPRESSED);
writer.writeDictionaryPage(new DictionaryPage(
BytesInput.concat(BytesInput.fromInt(10), BytesInput.fromInt(20), BytesInput.fromInt(30)),
3,
PLAIN));
writer.writeDataPage(
2,
2 * Integer.BYTES,
BytesInput.concat(BytesInput.fromInt(41), BytesInput.fromInt(42)),
Statistics.createStats(type),
RLE,
RLE,
PLAIN);
writer.endColumn();
writer.endBlock();
writer.end(Map.of());
}

try (ParquetFileReader reader = ParquetFileReader.open(HadoopInputFile.fromPath(path, conf))) {
ColumnChunkMetaData column =
reader.getRowGroups().get(0).getColumns().get(0);
assertThat(column.getEncodingStats().hasDictionaryPages()).isTrue();
assertThat(column.hasDictionaryPage()).isFalse();
assertThat(column.getDictionaryPageOffset()).isPositive().isLessThan(column.getFirstDataPageOffset());
}
try (ParquetReader<Group> reader = ParquetReader.builder(new GroupReadSupport(), path)
.withConf(conf)
.build()) {
assertThat(reader.read().getInteger("value", 0)).isEqualTo(41);
assertThat(reader.read().getInteger("value", 0)).isEqualTo(42);
assertThat(reader.read()).isNull();
}

withLogger((console, events) -> {
ShowPagesCommand command = new ShowPagesCommand(console);
command.targets = List.of(path.toString());
command.setConf(conf);
assertThat(command.run()).isZero();
List<String> pageLines = events.stream()
.map(LoggingEvent::getMessage)
.filter(line -> line.trim().startsWith("0-"))
.toList();
assertThat(pageLines).hasSize(2);
assertThat(pageLines.get(0))
.contains("dict")
.contains(String.format("%-7d %-10s %-10s", 3, humanReadable(4.0f), humanReadable(12L)));
assertThat(pageLines.get(1))
.contains("data")
.contains(String.format("%-7d %-10s %-10s", 2, humanReadable(4.0f), humanReadable(8L)));
});
}

@ParameterizedTest
@CsvSource({
"GZIP, PARQUET_1_0, true",
"GZIP, PARQUET_2_0, true",
"UNCOMPRESSED, PARQUET_1_0, true",
"UNCOMPRESSED, PARQUET_2_0, true",
"GZIP, PARQUET_1_0, false",
"GZIP, PARQUET_2_0, false",
"UNCOMPRESSED, PARQUET_1_0, false",
"UNCOMPRESSED, PARQUET_2_0, false"
})
public void testPageSizesMatchHeaders(CompressionCodecName codec, WriterVersion version, boolean dictionaryEnabled)
throws IOException {
Path path = new Path(randomParquetFile().toURI());
Configuration conf = new Configuration();
MessageType schema =
Types.buildMessage().required(BINARY).named("color").named("schema");
SimpleGroupFactory groups = new SimpleGroupFactory(schema);
try (ParquetWriter<Group> writer = ExampleParquetWriter.builder(path)
.withConf(conf)
.withType(schema)
.withCompressionCodec(codec)
.withWriterVersion(version)
.withDictionaryEncoding(dictionaryEnabled)
.build()) {
for (int i = 0; i < 200; i++) {
writer.write(
groups.newGroup().append("color", String.valueOf(i % 2).repeat(120)));
}
}

withLogger((console, events) -> {
ShowPagesCommand command = new ShowPagesCommand(console);
command.targets = Arrays.asList(path.toString());
command.setConf(conf);
assertThat(command.run()).isZero();
List<String> pageLines = events.stream()
.map(LoggingEvent::getMessage)
.filter(line -> line.trim().startsWith("0-"))
.toList();
assertThat(pageLines).hasSize(dictionaryEnabled ? 2 : 1);

HadoopInputFile file = HadoopInputFile.fromPath(path, conf);
try (ParquetFileReader reader = ParquetFileReader.open(file);
SeekableInputStream input = file.newStream()) {
ColumnChunkMetaData column =
reader.getRowGroups().get(0).getColumns().get(0);
assertThat(column.hasDictionaryPage()).isEqualTo(dictionaryEnabled);
input.seek(column.getStartingPos());
for (int i = 0; i < pageLines.size(); i++) {
PageHeader header = Util.readPageHeader(input);
int count = 200;
if (dictionaryEnabled && i == 0) {
assertThat(header.getType()).isEqualTo(PageType.DICTIONARY_PAGE);
count = header.getDictionary_page_header().getNum_values();
if (codec == CompressionCodecName.GZIP) {
assertThat(header.getCompressed_page_size()).isLessThan(header.getUncompressed_page_size());
}
} else {
assertThat(header.getType())
.isEqualTo(
version == WriterVersion.PARQUET_1_0
? PageType.DATA_PAGE
: PageType.DATA_PAGE_V2);
}
long size = header.getCompressed_page_size();
assertThat(pageLines.get(i))
.contains(String.format(
"%-7d %-10s %-10s",
count, humanReadable((float) size / count), humanReadable(size)));
input.seek(input.getPos() + size);
}
}
});
}
}