org.apache.arrow.dataset.jni

Class JniWrapper

java.lang.Object

org.apache.arrow.dataset.jni.JniWrapper

public class JniWrapper
extends Object

JNI wrapper for Dataset API's native implementation.

Method Summary

Modifier and Type	Method and Description
void	closeDataset(long datasetId) Release the Dataset by destroying its reference held by JNI wrapper.
void	closeDatasetFactory(long datasetFactoryId) Release the DatasetFactory by destroying its reference held by JNI wrapper.
void	closeScanner(long scannerId) Release the Scanner by destroying its reference held by JNI wrapper.
long	createDataset(long datasetFactoryId, byte[] schema) Create Dataset from a DatasetFactory and get the native pointer of the Dataset.
long	createScanner(long datasetId, String[] columns, long batchSize, long memoryPool) Create Scanner from a Dataset and get the native pointer of the Dataset.
static JniWrapper	get()
byte[]	getSchemaFromScanner(long scannerId) Get a serialized schema from native instance of a Scanner.
byte[]	inspectSchema(long datasetFactoryId) Get a serialized schema from native instance of a DatasetFactory.
boolean	nextRecordBatch(long scannerId, long arrowArray) Read next record batch from the specified scanner.
void	releaseBuffer(long bufferId) Release the Buffer by destroying its reference held by JNI wrapper.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

get

public static JniWrapper get()

closeDatasetFactory

public void closeDatasetFactory(long datasetFactoryId)

Release the DatasetFactory by destroying its reference held by JNI wrapper.

Parameters:

datasetFactoryId - the native pointer of the arrow::dataset::DatasetFactory instance.

inspectSchema

public byte[] inspectSchema(long datasetFactoryId)

Get a serialized schema from native instance of a DatasetFactory.

Parameters:

datasetFactoryId - the native pointer of the arrow::dataset::DatasetFactory instance.

Returns:

the serialized schema

See Also:

Schema

createDataset

public long createDataset(long datasetFactoryId,
                          byte[] schema)

Create Dataset from a DatasetFactory and get the native pointer of the Dataset.

Parameters:

datasetFactoryId - the native pointer of the arrow::dataset::DatasetFactory instance.

schema - the predefined schema of the resulting Dataset.

Returns:

the native pointer of the arrow::dataset::Dataset instance.

closeDataset

public void closeDataset(long datasetId)

Release the Dataset by destroying its reference held by JNI wrapper.

Parameters:

datasetId - the native pointer of the arrow::dataset::Dataset instance.

createScanner

public long createScanner(long datasetId,
                          String[] columns,
                          long batchSize,
                          long memoryPool)

Create Scanner from a Dataset and get the native pointer of the Dataset.

Parameters:

datasetId - the native pointer of the arrow::dataset::Dataset instance.

columns - desired column names. Columns not in this list will not be emitted when performing scan operation. Null equals to "all columns".

batchSize - batch size of scanned record batches.

memoryPool - identifier of memory pool used in the native scanner.

Returns:

the native pointer of the arrow::dataset::Scanner instance.

getSchemaFromScanner

public byte[] getSchemaFromScanner(long scannerId)

Get a serialized schema from native instance of a Scanner.

Parameters:

scannerId - the native pointer of the arrow::dataset::Scanner instance.

Returns:

the serialized schema

See Also:

Schema

closeScanner

public void closeScanner(long scannerId)

Release the Scanner by destroying its reference held by JNI wrapper.

Parameters:

scannerId - the native pointer of the arrow::dataset::Scanner instance.

nextRecordBatch

public boolean nextRecordBatch(long scannerId,
                               long arrowArray)

Read next record batch from the specified scanner.

Parameters:

scannerId - the native pointer of the arrow::dataset::Scanner instance.

arrowArray - pointer to an empty ArrowArray struct to store C++ side record batch that conforms to C data interface.

Returns:

true if valid record batch is returned; false if stream ended.

releaseBuffer

public void releaseBuffer(long bufferId)

Release the Buffer by destroying its reference held by JNI wrapper.

Parameters:

bufferId - the native pointer of the arrow::Buffer instance.