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https://issues.apache.org/jira/browse/ARROW-15971?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17509875#comment-17509875
]
David Li commented on ARROW-15971:
----------------------------------
This is basically the same, but I guess now it's a question of semantics: what
should {{setPosition(0);}} do when the length is 0? Arguably,
{{IndexOutOfBounds}} exception is logical and the special-casing for an empty
buffer is only for an edge case in Java.
{noformat}
>>> pa.array([], pa.list_(pa.int64())).buffers()
[None, <pyarrow.lib.Buffer object at 0x7f8aaf2b8c30>, None, <pyarrow.lib.Buffer
object at 0x7f8aaf2b8cb0>]
>>> pa.array([], pa.list_(pa.int64())).buffers()[1].to_pybytes()
b'\x00\x00\x00\x00'
>>> rb = pa.record_batch([pa.array([], pa.list_(pa.int64()))], names=["a"])
>>> writer = pa.ipc.new_stream('foo.arrows', rb.schema)
>>> writer.write_batch(rb)
>>> writer.close(){noformat}
{code:java}
import org.apache.arrow.memory.RootAllocator;
import org.apache.arrow.vector.ipc.ArrowStreamReader;
import org.apache.arrow.vector.VectorSchemaRoot;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;var allocator = new RootAllocator();
File file = new File("foo.arrows");
FileInputStream inputStream = new FileInputStream(file);
ArrowStreamReader reader = new ArrowStreamReader(inputStream, allocator);
reader.loadNextBatch()
reader.getVectorSchemaRoot().getVector("a").getReader()
var listReader = reader.getVectorSchemaRoot().getVector("a").getReader();
listReader.setPosition(0); {code}
fails with
{noformat}
| Exception java.lang.IndexOutOfBoundsException: index: 4, length: 4
(expected: range(0, 4))
| at ArrowBuf.checkIndexD (ArrowBuf.java:318)
| at ArrowBuf.chk (ArrowBuf.java:305)
| at ArrowBuf.getInt (ArrowBuf.java:424)
| at UnionListReader.setPosition (UnionListReader.java:64)
| at (#14:1) {noformat}
> [C++/Java] Error when reading inner lists within a struct in empty outer
> lists from C++/Python in Java
> ------------------------------------------------------------------------------------------------------
>
> Key: ARROW-15971
> URL: https://issues.apache.org/jira/browse/ARROW-15971
> Project: Apache Arrow
> Issue Type: Bug
> Components: C++, Java, Python
> Affects Versions: 7.0.0
> Reporter: Arrow User
> Priority: Major
> Labels: C++, bug, java
>
> When using C++ (or Python) to construct a null or empty outer array of type
> *array_1: list<item: struct<array_sub_col: list<item: string>>>*, either:
> {noformat}
> - array_1: null
> - array_1: []
> {noformat}
> an out of bounds exceptions (see stack trace below) follows when later
> retrieving the field reader for the inner list (*array_sub_col*) in Java,
> when trying to access the subsequent offset buffer:
> https://github.com/apache/arrow/blob/master/java/vector/src/main/java/org/apache/arrow/vector/complex/impl/UnionListReader.java#L64
> h2. Reproduction
> *Java*: 7.0.0
> *C++*: 7.0.0
> *Python*: 7.0.0
> Creating a stream on C++ of type *array_1: list<item: struct<array_sub_col:
> list<item: string>>>* with an empty (or null) outer list:
> {code:c++}arrow::MemoryPool* pool = arrow::default_memory_pool();
> arrow::Result<std::shared_ptr<arrow::io::BufferOutputStream>> stream_buffer =
> arrow::io::BufferOutputStream::Create(1, pool);
> std::vector<std::shared_ptr<arrow::Field>>
> inner_list_field{std::make_shared<arrow::Field>("array_sub_col",
> arrow::list(arrow::utf8()))};
> // Datatype for the builder: list<struct<list<string>>>
> std::shared_ptr<DataType> data_type = list(struct_(inner_list_field));
> std::unique_ptr<arrow::ArrayBuilder> builder;
> arrow::MakeBuilder(pool, data_type, &builder);
> auto* list_builder = dynamic_cast<arrow::ListBuilder*>(builder.get());
> // Append a null or an empty list to the outer list
> list_builder->AppendNull(); // or list_builder->AppendEmptyValue()
> std::vector<std::shared_ptr<arrow::Array>> value_batch;
> value_batch.resize(1);
> list_builder->Finish(&value_batch[0]);
> std::vector<std::shared_ptr<arrow::Field>>
> outer_list_field{std::make_shared<arrow::Field>("array_1",data_type)};
> auto schema = std::make_shared<arrow::Schema>(outer_list_field);
> // Build a single row record batch
> std::shared_ptr<arrow::RecordBatch> batch = RecordBatch::Make(schema, 1,
> value_batch);
> ASSERT_OK(batch->Validate());
> // Stream the batch to a file to later read on the Java side
> arrow::Result<std::shared_ptr<ipc::RecordBatchWriter>> stream_writer =
> arrow::ipc::MakeStreamWriter(stream_buffer.ValueOrDie().get(), schema,
> arrow::ipc::IpcWriteOptions::Defaults());
> stream_writer.ValueOrDie()->WriteRecordBatch(*batch);
> arrow::Result<std::shared_ptr<arrow::Buffer>> buffer_result =
> stream_buffer.ValueOrDie()->Finish();
> std::shared_ptr<arrow::Buffer> buffer = buffer_result.ValueOrDie();
> auto file_output =
> arrow::io::FileOutputStream::Open("/tmp/batch_stream.out").ValueOrDie();
> file_output->Write(buffer->data(), buffer->size());
> file_output->Close();
> {code}
> As expected, Python holds the same memory layout for the field vectors as the
> C++ code above:
> {code:python}array = pa.array([None],
> type=pa.list_(pa.struct([pa.field("array_sub_col", pa.list_(pa.utf8()))])))
> batch = pa.record_batch([struct_array], names=["array_1"])
> sink = pa.BufferOutputStream()
> with pa.ipc.new_stream(sink, batch.schema) as writer:
> writer.write_batch(batch)
> buf = sink.getvalue()
> with open('/tmp/batch_stream.out', 'wb') as f:
> f.write(buf)
> {code}
> *Java fails when then trying to access the inner list's field reader:*
> {code:java}File file = new File("/tmp/batch_stream.out");
> byte[] bytes = FileUtils.readFileToByteArray(file);
> try (ArrowStreamReader reader = new ArrowStreamReader(new
> ByteArrayInputStream(bytes), allocator)) {
> Schema schema = reader.getVectorSchemaRoot().getSchema();
> reader.loadNextBatch();
>
> readBatch.getVector("array_1").getReader().reader().reader("array_sub_col");
> // <- fails: reader("array_sub_col") fails with OOB
> // Concrete readers:
> // FieldVector array_1 = readBatch.getVector("array_1");
> // UnionListReader array_1_reader = (UnionListReader)
> array_1.getReader();
> // NullableStructReaderImpl struct_reader = (NullableStructReaderImpl)
> array_1_reader.reader();
> // FieldReader union_list_reader =
> struct_reader.reader("array_sub_col"); // <- fails: OOB
> {code}
> h3. Stack trace:
> {noformat}
> java.lang.reflect.InvocationTargetException
> at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
> at jdk.internal.reflect.NativeMethodAccessorImpl.invoke
> (NativeMethodAccessorImpl.java:62)
> at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke
> (DelegatingMethodAccessorImpl.java:43)
> at java.lang.reflect.Method.invoke (Method.java:566)
> at org.codehaus.mojo.exec.ExecJavaMojo$1.run (ExecJavaMojo.java:297)
> at java.lang.Thread.run (Thread.java:829)
> Caused by: java.lang.IndexOutOfBoundsException: index: 4, length: 4
> (expected: range(0, 4))
> at org.apache.arrow.memory.ArrowBuf.checkIndexD (ArrowBuf.java:318)
> at org.apache.arrow.memory.ArrowBuf.chk (ArrowBuf.java:305)
> at org.apache.arrow.memory.ArrowBuf.getInt (ArrowBuf.java:424)
> at com.test.arrow.ValidateArrow.testArrow (ValidateArrow.java:433)
> at com.test.arrow.ValidateArrow.main (ValidateArrow.java:440)
> at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
> at jdk.internal.reflect.NativeMethodAccessorImpl.invoke
> (NativeMethodAccessorImpl.java:62)
> at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke
> (DelegatingMethodAccessorImpl.java:43)
> at java.lang.reflect.Method.invoke (Method.java:566)
> at org.codehaus.mojo.exec.ExecJavaMojo$1.run (ExecJavaMojo.java:297)
> at java.lang.Thread.run (Thread.java:829)
> {noformat}
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