coderex2522 commented on issue #1220:
URL: https://github.com/apache/orc/issues/1220#issuecomment-1220202314
For List type, the length of the offset array is one greater than the number
of rows. Because the number of elements in the current row is confirmed by
offsets[row] - offsets[row - 1](row number>= 1). So your example code needs to
add the following two lines.
void write_orc()
{
using namespace orc;
ORC_UNIQUE_PTR<OutputStream> outStream = writeLocalFile("test-file.orc");
ORC_UNIQUE_PTR<Type> schema(
Type::buildTypeFromString("struct<id:int,list1:array<string>>"));
WriterOptions options;
ORC_UNIQUE_PTR<Writer> writer = createWriter(*schema, outStream.get(),
options);
std::unique_ptr<Writer> writer = createWriter(*type, stream.get(),
options);
uint64_t batch_size = 1024, row_count = 2048;
std::unique_ptr<ColumnVectorBatch> batch =
writer->createRowBatch(row_count);
StructVectorBatch &root_batch =
dynamic_cast<StructVectorBatch &>(*batch.get());
LongVectorBatch &id_batch =
dynamic_cast<LongVectorBatch &>(*struct_batch.fields[0]);
ListVectorBatch &list_batch =
dynamic_cast<ListVectorBatch &>(*struct_batch.fields[1]);
StringVectorBatch &str_batch =
dynamic_cast<StringVectorBatch &>(*list_batch.elements.get());
std::vector<std::string> vs{"str1", "str2"};
char **data = str_batch.data.data();
int64_t *offsets = list_batch.offsets.data();
uint64_t offset = 0, rows = 0;
for (size_t i = 0; i < row_count; ++i) {
offsets[rows] = static_cast<int64_t>(offset);
id_batch.data[rows] = articles[i]->get_id();
for (auto &s : vs)
{
data[offset] = &s[0];
str_batch.length[offset++] = s.size();
}
rows++;
if (rows == batch_size)
{
offsets[rows] = offset; // new line
root_batch.numElements = rows;
id_batch.numElements = rows;
list_batch.numElements = rows;
writer->add(*batch);
rows = 0;
offset = 0;
}
}
if (rows != 0)
{
offsets[rows] = offset; // new line
root_batch.numElements = rows;
id_batch.numElements = rows;
list_batch.numElements = rows;
writer->add(*batch);
rows = 0;
offset = 0;
}
writer->close();
}
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