vibhatha commented on code in PR #41967:
URL: https://github.com/apache/arrow/pull/41967#discussion_r1632512141
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java/c/src/main/java/org/apache/arrow/c/ArrayExporter.java:
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@@ -96,8 +97,34 @@ void export(ArrowArray array, FieldVector vector,
DictionaryProvider dictionaryP
}
if (buffers != null) {
+ final long bufferSize = buffers.size();
+ /*
+ * For Variadic types, an additional buffer is kept to store
+ * the size of each variadic buffer since that information
+ * cannot be retrieved in the import component.
+ * Here, the dataBufferReqCount is calculated to determine
+ * the additional number of buffers required.
+ * Also note that if the bufferSize is greater than 2, it means
+ * there is one or more data buffers.
+ * Thus, the dataBufferReqCount is set to 1 to get additional buffer
+ * for to store variadic size buffer.
+ * If it is not the case, the dataBuffer is not present.
+ * According to the spec and C Data interface in C++, there must be
+ * at least 3 data buffers present at the import component.
+ * Thus, the dataBufferReqCount is set to 2 to get additional buffer
+ * for empty dataBuffer and the variadic size buffer.
+ */
+ int dataBufferReqCount = 0;
+ if (vector instanceof BaseVariableWidthViewVector) {
Review Comment:
I couldn't agree more. I was hesitant to change the C Data interface as it
is a public API.
But some thoughts...
In `Data.java` we call the `exportVector(...)` which ultimately calls
`ArrowExporter.exprt(...)`. And since we recently updated `ArrowRecordBatch`
with `variadicBufferCounts` would it be okay/feasible if we just pass it here
by introducing a new function
```
public static void exportVector(BufferAllocator allocator, FieldVector
vector, DictionaryProvider provider,
ArrowArray out, ArrowSchema outSchema, List<Integer>
variadicBufferCounts) {
....
}
```
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