amol- commented on a change in pull request #136: URL: https://github.com/apache/arrow-cookbook/pull/136#discussion_r809887254
########## File path: java/source/io.rst ########## @@ -0,0 +1,542 @@ +.. _arrow-io: + +======================== +Reading and writing data +======================== + +The `Arrow IPC format <https://arrow.apache.org/docs/java/ipc.html>`_ defines two types of binary formats +for serializing Arrow data: the streaming format and the file format (or random access format). Such files can +be directly memory-mapped when read. + +.. contents:: + +Writing +======= + +Both writing file and streaming formats use the same API. + +Writing Random Access Files +*************************** + +Write - Out to File +------------------- + +.. testcode:: + + import org.apache.arrow.memory.RootAllocator; + import org.apache.arrow.vector.VarCharVector; + import org.apache.arrow.vector.IntVector; + import org.apache.arrow.vector.types.pojo.Field; + import org.apache.arrow.vector.types.pojo.FieldType; + import org.apache.arrow.vector.types.pojo.ArrowType; + import org.apache.arrow.vector.types.pojo.Schema; + import org.apache.arrow.vector.VectorSchemaRoot; + import static java.util.Arrays.asList; + import org.apache.arrow.vector.ipc.ArrowFileWriter; + + import java.io.File; + import java.io.FileOutputStream; + import java.io.IOException; + + try (RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE)) { + Field name = new Field("name", FieldType.nullable(new ArrowType.Utf8()), null); + Field age = new Field("age", FieldType.nullable(new ArrowType.Int(32, true)), null); + Schema schemaPerson = new Schema(asList(name, age)); + try(VectorSchemaRoot vectorSchemaRoot = VectorSchemaRoot.create(schemaPerson, rootAllocator)){ + VarCharVector nameVector = (VarCharVector) vectorSchemaRoot.getVector("name"); + nameVector.allocateNew(3); + nameVector.set(0, "David".getBytes()); + nameVector.set(1, "Gladis".getBytes()); + nameVector.set(2, "Juan".getBytes()); + IntVector ageVector = (IntVector) vectorSchemaRoot.getVector("age"); + ageVector.allocateNew(3); + ageVector.set(0, 10); + ageVector.set(1, 20); + ageVector.set(2, 30); + vectorSchemaRoot.setRowCount(3); + File file = new File("randon_access_to_file.arrow"); + try (FileOutputStream fileOutputStream = new FileOutputStream(file); + ArrowFileWriter writer = new ArrowFileWriter(vectorSchemaRoot, null, fileOutputStream.getChannel()) + ) { + writer.start(); + for (int i = 0; i < 10; i++) { + // All the data that is going to write comes from the root and as we were not changing root data we are writing the same data 10x times + writer.writeBatch(); + } + writer.end(); + System.out.println("Record batches written: " + writer.getRecordBlocks().size()); + } catch (IOException e) { + e.printStackTrace(); + } + } + } + +.. testoutput:: + + Record batches written: 10 + +Write - Out to Buffer +--------------------- + +.. testcode:: + + import org.apache.arrow.memory.RootAllocator; + import org.apache.arrow.vector.VarCharVector; + import org.apache.arrow.vector.IntVector; + import org.apache.arrow.vector.types.pojo.Field; + import org.apache.arrow.vector.types.pojo.FieldType; + import org.apache.arrow.vector.types.pojo.ArrowType; + import org.apache.arrow.vector.types.pojo.Schema; + import org.apache.arrow.vector.VectorSchemaRoot; + import static java.util.Arrays.asList; + import org.apache.arrow.vector.ipc.ArrowFileWriter; + + import java.io.ByteArrayOutputStream; + import java.io.IOException; + import java.nio.channels.Channels; + + try (RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE)) { + Field name = new Field("name", FieldType.nullable(new ArrowType.Utf8()), null); + Field age = new Field("age", FieldType.nullable(new ArrowType.Int(32, true)), null); + Schema schemaPerson = new Schema(asList(name, age)); + try(VectorSchemaRoot vectorSchemaRoot = VectorSchemaRoot.create(schemaPerson, rootAllocator)){ + VarCharVector nameVector = (VarCharVector) vectorSchemaRoot.getVector("name"); + nameVector.allocateNew(3); + IntVector ageVector = (IntVector) vectorSchemaRoot.getVector("age"); + ageVector.allocateNew(3); + vectorSchemaRoot.setRowCount(3); + try (ByteArrayOutputStream out = new ByteArrayOutputStream(); + ArrowFileWriter writer = new ArrowFileWriter(vectorSchemaRoot, null, Channels.newChannel(out))) + { + writer.start(); + for (int i=0; i<10; i++){ + nameVector.set(0, ("New-"+(i+1)).getBytes()); + nameVector.set(1, ("New-"+(i+1)).getBytes()); + nameVector.set(2, ("New-"+(i+1)).getBytes()); + ageVector.set(0, (i+2)*10); + ageVector.set(1, (i+2)*20); + ageVector.set(2, (i+2)*30); + writer.writeBatch(); + } + System.out.println("Record batches written: " + writer.getRecordBlocks().size()); + } catch (IOException e) { + e.printStackTrace(); + } + } + } + +.. testoutput:: + + Record batches written: 10 + +Writing Streaming Format +************************ + +Write - Out to File +------------------- + +.. testcode:: + + import org.apache.arrow.memory.RootAllocator; + import org.apache.arrow.vector.VarCharVector; + import org.apache.arrow.vector.IntVector; + import org.apache.arrow.vector.types.pojo.Field; + import org.apache.arrow.vector.types.pojo.FieldType; + import org.apache.arrow.vector.types.pojo.ArrowType; + import org.apache.arrow.vector.types.pojo.Schema; + import org.apache.arrow.vector.VectorSchemaRoot; + import static java.util.Arrays.asList; + import org.apache.arrow.vector.ipc.ArrowStreamWriter; + import java.io.File; + import java.io.FileOutputStream; + import java.io.IOException; + + try (RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE)) { + // Create and populate data: + Field name = new Field("name", FieldType.nullable(new ArrowType.Utf8()), null); + Field age = new Field("age", FieldType.nullable(new ArrowType.Int(32, true)), null); + Schema schemaPerson = new Schema(asList(name, age)); + try(VectorSchemaRoot vectorSchemaRoot = VectorSchemaRoot.create(schemaPerson, rootAllocator)){ + VarCharVector nameVector = (VarCharVector) vectorSchemaRoot.getVector("name"); + nameVector.allocateNew(3); + nameVector.set(0, "David".getBytes()); + nameVector.set(1, "Gladis".getBytes()); + nameVector.set(2, "Juan".getBytes()); + IntVector ageVector = (IntVector) vectorSchemaRoot.getVector("age"); + ageVector.allocateNew(3); + ageVector.set(0, 10); + ageVector.set(1, 20); + ageVector.set(2, 30); + vectorSchemaRoot.setRowCount(3); + File file = new File("streaming_to_file.arrow"); + try (FileOutputStream fileOutputStream = new FileOutputStream(file); + ArrowStreamWriter writer = new ArrowStreamWriter(vectorSchemaRoot, null, fileOutputStream.getChannel()) + ){ + writer.start(); + for (int i=0; i<10; i++){ Review comment: same as before -- This is an automated message from the Apache Git Service. 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