Github user jihoonson commented on a diff in the pull request:
— Diff: tajo-docs/src/main/sphinx/table_management/orc.rst —
@@ -0,0 +1,48 @@
+*ORC(Optimized Row Columnar)* is a columnar storage format from Hive. ORC improves performance for reading,
+writing, and processing data.
+For more details, please refer to `ORC Files <https://cwiki.apache.org/confluence/display/Hive/LanguageManual+ORC>`_ at Hive wiki.
+How to Create a ORC Table?
+If you are not familiar with ``CREATE TABLE`` statement, please refer to Data Definition Language :doc:`/sql_language/ddl`.
+In order to specify a certain file format for your table, you need to use the ``USING`` clause in your ``CREATE TABLE``
+statement. Below is an example statement for creating a table using orc files.
+.. code-block:: sql
+ CREATE TABLE table1 (
+ id int,
+ name text,
+ score float,
+ type text
+ ) USING orc;
+Some table storage formats provide parameters for enabling or disabling features and adjusting physical parameters.
+The ``WITH`` clause in the CREATE TABLE statement allows users to set those parameters.
+Now, ORC file provides the following physical properties.
+* ``orc.max.merge.distance``: Reading property. When stripes are too closer and the distance is lower than this value, they are merged and read at once. Default is 1MB.
+* ``orc.stripe.size``: Writing property. It decides size of each stripe. Default is 64MB.
+* ``orc.compression.kind``: Writing property. The compression algorithm used to compress data. It should be one of ``none``, ``snappy``, ``zlib``. Default is ``none``.
+* ``orc.buffer.size``: Writing property. It decides size of writing buffer. Default is 256KB.
+* ``orc.rowindex.stride``: Writing property. Define the default ORC index stride in number of rows. (Stride is the number of rows an index entry represents.) Default is 10000.
+Compatibility Issues with Apache Hive™
+At the moment, Tajo only supports flat relational tables.
+As a result, Tajo's ORC storage type does not support nested schemas.
+However, we are currently working on adding support for nested schemas and non-scalar types (`TAJO-710 <https://issues.apache.org/jira/browse/TAJO-710>`_).
— End diff –
I think that this sentence is redundant. It would be enough if tajo currently supports only flat schema.