amoeba commented on code in PR #14452:
URL: https://github.com/apache/arrow/pull/14452#discussion_r999981582
##########
docs/source/cpp/csv.rst:
##########
@@ -25,15 +25,24 @@ Reading and Writing CSV files
=============================
Arrow provides a fast CSV reader allowing ingestion of external data
-as Arrow tables.
+as Arrow Tables or streamed as Arrow RecordBatches.
.. seealso::
:ref:`CSV reader/writer API reference <cpp-api-csv>`.
-Basic usage
-===========
+Reading CSV files
+=================
+
+Data in a CSV file can either be read in as a single Arrow Table using
+:class:`~arrow::csv::TableReader` or streamed as RecordBatches using
+:class:`~arrow::csv::StreamingReader`. See :ref:`Tradeoffs <tradeoffs>` for a
+discussion of the tradeoffs between the two methods.
+
+TableReader
+-----------
-A CSV file is read from a :class:`~arrow::io::InputStream`.
+The :class:`~arrow::csv::TableReader` class requires an
+:class:`::arrow::io::InputStream` instance representing the input file.
Review Comment:
This is a good improvement, thanks.
##########
docs/source/cpp/csv.rst:
##########
@@ -56,19 +65,88 @@ A CSV file is read from a :class:`~arrow::io::InputStream`.
parse_options,
convert_options);
if (!maybe_reader.ok()) {
- // Handle TableReader instantiation error...
+ // Handle TableReader instantiation error...
}
std::shared_ptr<arrow::csv::TableReader> reader = *maybe_reader;
// Read table from CSV file
auto maybe_table = reader->Read();
if (!maybe_table.ok()) {
- // Handle CSV read error
- // (for example a CSV syntax error or failed type conversion)
+ // Handle CSV read error
+ // (for example a CSV syntax error or failed type conversion)
}
std::shared_ptr<arrow::Table> table = *maybe_table;
}
+Behavior of :class:`~arrow::csv::TableReader` can be customized using a
+combination of :class:`~arrow::csv::ReadOptions`,
+:class:`~arrow::csv::ParseOptions`, and :class:`~arrow::csv::ConvertOptions`.
+
+StreamingReader
+---------------
+
+The :class:`~arrow::csv::StreamingReader` class requires an
+:class:`::arrow::io::InputStream` instance representing the input file.
+
+.. code-block:: cpp
+
+ #include "arrow/csv/api.h"
+
+ {
+ // ...
+ arrow::io::IOContext io_context = arrow::io::default_io_context();
+ std::shared_ptr<arrow::io::InputStream> input = ...;
+
+ auto read_options = arrow::csv::ReadOptions::Defaults();
+ auto parse_options = arrow::csv::ParseOptions::Defaults();
+ auto convert_options = arrow::csv::ConvertOptions::Defaults();
+
+ // Instantiate StreamingReader from input stream and options
+ auto maybe_reader =
+ arrow::csv::StreamingReader::Make(io_context,
+ input,
+ read_options,
+ parse_options,
+ convert_options);
+ if (!maybe_reader.ok()) {
+ // Handle StreamingReader instantiation error...
+ }
+ std::shared_ptr<arrow::csv::StreamingReader> reader = *maybe_reader;
+
+ // Set aside a RecordBatch pointer for re-use while streaming
+ std::shared_ptr<RecordBatch> batch;
+
+ // Attempt to read the first RecordBatch
+ reader->ReadNext(&batch);
+
+ if (batch == NULL) {
+ // Handle end of file
+ }
+ }
+
+Behavior of :class:`~arrow::csv::StreamingReader` can be customized using a
+combination of :class:`~arrow::csv::ReadOptrions`,
+:class:`~arrow::csv::ParseOptions`, and :class:`~arrow::csv::ConvertOptions`.
+
+.. _tradeoffs:
Review Comment:
Done.
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