# [Apache ORC](https://orc.apache.org/)
ORC is a self-describing type-aware columnar file format designed for
Hadoop workloads. It is optimized for large streaming reads, but with
integrated support for finding required rows quickly. Storing data in
a columnar format lets the reader read, decompress, and process only
the values that are required for the current query. Because ORC files
are type-aware, the writer chooses the most appropriate encoding for
the type and builds an internal index as the file is written.
Predicate pushdown uses those indexes to determine which stripes in a
file need to be read for a particular query and the row indexes can
narrow the search to a particular set of 10,000 rows. ORC supports the
complete set of types in Hive, including the complex types: structs,
lists, maps, and unions.
## ORC File Library
This project includes both a Java library and a C++ library for reading and writing the _Optimized Row Columnar_ (ORC) file format. The C++ and Java libraries are completely independent of each other and will each read all versions of ORC files.
Releases:
* Latest: Apache ORC releases
* Maven Central: 
* Downloads: Apache ORC downloads
* Release tags: Apache ORC release tags
* Plan: Apache ORC future release plan
The current build status:
* Main branch
Bug tracking: Apache Jira
The subdirectories are:
* c++ - the c++ reader and writer
* cmake_modules - the cmake modules
* docker - docker scripts to build and test on various linuxes
* examples - various ORC example files that are used to test compatibility
* java - the java reader and writer
* proto - the protocol buffer definition for the ORC metadata
* site - the website and documentation
* tools - the c++ tools for reading and inspecting ORC files
### Building
* Install java 1.8 or higher
* Install maven 3.8.6 or higher
* Install cmake
To build a release version with debug information:
```shell
% mkdir build
% cd build
% cmake ..
% make package
% make test-out
```
To build a debug version:
```shell
% mkdir build
% cd build
% cmake .. -DCMAKE_BUILD_TYPE=DEBUG
% make package
% make test-out
```
To build a release version without debug information:
```shell
% mkdir build
% cd build
% cmake .. -DCMAKE_BUILD_TYPE=RELEASE
% make package
% make test-out
```
To build only the Java library:
```shell
% cd java
% ./mvnw package
```
To build only the C++ library:
```shell
% mkdir build
% cd build
% cmake .. -DBUILD_JAVA=OFF
% make package
% make test-out
```