Java tutorial
/* * Licensed 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 com.facebook.presto.parquet.reader; import org.apache.hadoop.fs.FSDataInputStream; import org.apache.hadoop.fs.FileSystem; import org.apache.hadoop.fs.Path; import parquet.format.ColumnChunk; import parquet.format.ColumnMetaData; import parquet.format.ConvertedType; import parquet.format.Encoding; import parquet.format.FileMetaData; import parquet.format.KeyValue; import parquet.format.RowGroup; import parquet.format.SchemaElement; import parquet.format.Statistics; import parquet.format.Type; import parquet.hadoop.metadata.BlockMetaData; import parquet.hadoop.metadata.ColumnChunkMetaData; import parquet.hadoop.metadata.ColumnPath; import parquet.hadoop.metadata.CompressionCodecName; import parquet.hadoop.metadata.ParquetMetadata; import parquet.schema.MessageType; import parquet.schema.OriginalType; import parquet.schema.PrimitiveType.PrimitiveTypeName; import parquet.schema.Type.Repetition; import parquet.schema.Types; import java.io.EOFException; import java.io.IOException; import java.io.InputStream; import java.util.ArrayList; import java.util.Arrays; import java.util.Collections; import java.util.HashMap; import java.util.HashSet; import java.util.Iterator; import java.util.List; import java.util.Locale; import java.util.Map; import java.util.Set; import static com.facebook.presto.parquet.ParquetValidationUtils.validateParquet; import static java.nio.charset.StandardCharsets.US_ASCII; import static parquet.format.Util.readFileMetaData; public final class MetadataReader { private static final int PARQUET_METADATA_LENGTH = 4; private static final byte[] MAGIC = "PAR1".getBytes(US_ASCII); private MetadataReader() { } public static ParquetMetadata readFooter(FileSystem fileSystem, Path file, long fileSize) throws IOException { try (FSDataInputStream inputStream = fileSystem.open(file)) { return readFooter(inputStream, file, fileSize); } } public static ParquetMetadata readFooter(FSDataInputStream inputStream, Path file, long fileSize) throws IOException { // Parquet File Layout: // // MAGIC // variable: Data // variable: Metadata // 4 bytes: MetadataLength // MAGIC validateParquet(fileSize >= MAGIC.length + PARQUET_METADATA_LENGTH + MAGIC.length, "%s is not a valid Parquet File", file); long metadataLengthIndex = fileSize - PARQUET_METADATA_LENGTH - MAGIC.length; inputStream.seek(metadataLengthIndex); int metadataLength = readIntLittleEndian(inputStream); byte[] magic = new byte[MAGIC.length]; inputStream.readFully(magic); validateParquet(Arrays.equals(MAGIC, magic), "Not valid Parquet file: %s expected magic number: %s got: %s", file, Arrays.toString(MAGIC), Arrays.toString(magic)); long metadataIndex = metadataLengthIndex - metadataLength; validateParquet(metadataIndex >= MAGIC.length && metadataIndex < metadataLengthIndex, "Corrupted Parquet file: %s metadata index: %s out of range", file, metadataIndex); inputStream.seek(metadataIndex); FileMetaData fileMetaData = readFileMetaData(inputStream); List<SchemaElement> schema = fileMetaData.getSchema(); validateParquet(!schema.isEmpty(), "Empty Parquet schema in file: %s", file); MessageType messageType = readParquetSchema(schema); List<BlockMetaData> blocks = new ArrayList<>(); List<RowGroup> rowGroups = fileMetaData.getRow_groups(); if (rowGroups != null) { for (RowGroup rowGroup : rowGroups) { BlockMetaData blockMetaData = new BlockMetaData(); blockMetaData.setRowCount(rowGroup.getNum_rows()); blockMetaData.setTotalByteSize(rowGroup.getTotal_byte_size()); List<ColumnChunk> columns = rowGroup.getColumns(); validateParquet(!columns.isEmpty(), "No columns in row group: %s", rowGroup); String filePath = columns.get(0).getFile_path(); for (ColumnChunk columnChunk : columns) { validateParquet( (filePath == null && columnChunk.getFile_path() == null) || (filePath != null && filePath.equals(columnChunk.getFile_path())), "all column chunks of the same row group must be in the same file"); ColumnMetaData metaData = columnChunk.meta_data; String[] path = metaData.path_in_schema.stream().map(value -> value.toLowerCase(Locale.ENGLISH)) .toArray(String[]::new); ColumnPath columnPath = ColumnPath.get(path); PrimitiveTypeName primitiveTypeName = messageType.getType(columnPath.toArray()) .asPrimitiveType().getPrimitiveTypeName(); ColumnChunkMetaData column = ColumnChunkMetaData.get(columnPath, primitiveTypeName, CompressionCodecName.fromParquet(metaData.codec), readEncodings(metaData.encodings), readStats(metaData.statistics, primitiveTypeName), metaData.data_page_offset, metaData.dictionary_page_offset, metaData.num_values, metaData.total_compressed_size, metaData.total_uncompressed_size); blockMetaData.addColumn(column); } blockMetaData.setPath(filePath); blocks.add(blockMetaData); } } Map<String, String> keyValueMetaData = new HashMap<>(); List<KeyValue> keyValueList = fileMetaData.getKey_value_metadata(); if (keyValueList != null) { for (KeyValue keyValue : keyValueList) { keyValueMetaData.put(keyValue.key, keyValue.value); } } return new ParquetMetadata(new parquet.hadoop.metadata.FileMetaData(messageType, keyValueMetaData, fileMetaData.getCreated_by()), blocks); } private static MessageType readParquetSchema(List<SchemaElement> schema) { Iterator<SchemaElement> schemaIterator = schema.iterator(); SchemaElement rootSchema = schemaIterator.next(); Types.MessageTypeBuilder builder = Types.buildMessage(); readTypeSchema(builder, schemaIterator, rootSchema.getNum_children()); return builder.named(rootSchema.name); } private static void readTypeSchema(Types.GroupBuilder<?> builder, Iterator<SchemaElement> schemaIterator, int typeCount) { for (int i = 0; i < typeCount; i++) { SchemaElement element = schemaIterator.next(); Types.Builder<?, ?> typeBuilder; if (element.type == null) { typeBuilder = builder.group(Repetition.valueOf(element.repetition_type.name())); readTypeSchema((Types.GroupBuilder<?>) typeBuilder, schemaIterator, element.num_children); } else { Types.PrimitiveBuilder<?> primitiveBuilder = builder.primitive(getTypeName(element.type), Repetition.valueOf(element.repetition_type.name())); if (element.isSetType_length()) { primitiveBuilder.length(element.type_length); } if (element.isSetPrecision()) { primitiveBuilder.precision(element.precision); } if (element.isSetScale()) { primitiveBuilder.scale(element.scale); } typeBuilder = primitiveBuilder; } if (element.isSetConverted_type()) { typeBuilder.as(getOriginalType(element.converted_type)); } if (element.isSetField_id()) { typeBuilder.id(element.field_id); } typeBuilder.named(element.name.toLowerCase(Locale.ENGLISH)); } } public static parquet.column.statistics.Statistics<?> readStats(Statistics statistics, PrimitiveTypeName type) { parquet.column.statistics.Statistics<?> stats = parquet.column.statistics.Statistics .getStatsBasedOnType(type); if (statistics != null) { if (statistics.isSetMax() && statistics.isSetMin()) { stats.setMinMaxFromBytes(statistics.min.array(), statistics.max.array()); } stats.setNumNulls(statistics.null_count); } return stats; } private static Set<parquet.column.Encoding> readEncodings(List<Encoding> encodings) { Set<parquet.column.Encoding> columnEncodings = new HashSet<>(); for (Encoding encoding : encodings) { columnEncodings.add(parquet.column.Encoding.valueOf(encoding.name())); } return Collections.unmodifiableSet(columnEncodings); } private static PrimitiveTypeName getTypeName(Type type) { switch (type) { case BYTE_ARRAY: return PrimitiveTypeName.BINARY; case INT64: return PrimitiveTypeName.INT64; case INT32: return PrimitiveTypeName.INT32; case BOOLEAN: return PrimitiveTypeName.BOOLEAN; case FLOAT: return PrimitiveTypeName.FLOAT; case DOUBLE: return PrimitiveTypeName.DOUBLE; case INT96: return PrimitiveTypeName.INT96; case FIXED_LEN_BYTE_ARRAY: return PrimitiveTypeName.FIXED_LEN_BYTE_ARRAY; default: throw new IllegalArgumentException("Unknown type " + type); } } private static OriginalType getOriginalType(ConvertedType type) { switch (type) { case UTF8: return OriginalType.UTF8; case MAP: return OriginalType.MAP; case MAP_KEY_VALUE: return OriginalType.MAP_KEY_VALUE; case LIST: return OriginalType.LIST; case ENUM: return OriginalType.ENUM; case DECIMAL: return OriginalType.DECIMAL; case DATE: return OriginalType.DATE; case TIME_MILLIS: return OriginalType.TIME_MILLIS; case TIMESTAMP_MILLIS: return OriginalType.TIMESTAMP_MILLIS; case INTERVAL: return OriginalType.INTERVAL; case INT_8: return OriginalType.INT_8; case INT_16: return OriginalType.INT_16; case INT_32: return OriginalType.INT_32; case INT_64: return OriginalType.INT_64; case UINT_8: return OriginalType.UINT_8; case UINT_16: return OriginalType.UINT_16; case UINT_32: return OriginalType.UINT_32; case UINT_64: return OriginalType.UINT_64; case JSON: return OriginalType.JSON; case BSON: return OriginalType.BSON; default: throw new IllegalArgumentException("Unknown converted type " + type); } } private static int readIntLittleEndian(InputStream in) throws IOException { int ch1 = in.read(); int ch2 = in.read(); int ch3 = in.read(); int ch4 = in.read(); if ((ch1 | ch2 | ch3 | ch4) < 0) { throw new EOFException(); } return ((ch4 << 24) + (ch3 << 16) + (ch2 << 8) + (ch1)); } }