docs/source/cpp/examples/dataset_skyhook_scan_example.rst

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=====================
Arrow Skyhook example
=====================

The file ``cpp/examples/arrow/dataset_skyhook_scan_example.cc``
located inside the source tree contains an example of using Skyhook to
offload filters and projections to a Ceph cluster.

Instructions
============

.. note::
   The instructions below are for Ubuntu 20.04 or above.

1. Install Ceph and Skyhook dependencies.

   .. code-block:: bash

      apt update
      apt install -y cmake \
                     libradospp-dev \
                     rados-objclass-dev \
                     ceph \
                     ceph-common \
                     ceph-osd \
                     ceph-mon \
                     ceph-mgr \
                     ceph-mds \
                     rbd-mirror \
                     ceph-fuse \
                     rapidjson-dev \
                     libboost-all-dev \
                     python3-pip

2. Build and install Skyhook.

   .. code-block:: bash

      git clone https://github.com/apache/arrow
      cd arrow/
      mkdir -p cpp/release
      cd cpp/release
      cmake -DARROW_SKYHOOK=ON \
            -DARROW_PARQUET=ON \
            -DARROW_WITH_SNAPPY=ON \
            -DARROW_BUILD_EXAMPLES=ON \
            -DARROW_DATASET=ON \
            -DARROW_CSV=ON \
            -DARROW_WITH_LZ4=ON \
            ..

      make -j install
      cp release/libcls_skyhook.so /usr/lib/x86_64-linux-gnu/rados-classes/

3. Deploy a Ceph cluster with a single in-memory OSD using `this <https://github.com/uccross/skyhookdm/blob/master/scripts/micro-osd.sh>`_ script.

   .. code-block:: bash

      ./micro-osd.sh /tmp/skyhook

4. Generate the example dataset.

   .. code-block:: bash

      pip install pandas pyarrow
      python3 ../../ci/scripts/generate_dataset.py
      cp -r nyc /mnt/cephfs/

5. Execute the example.

   .. code-block:: bash

      LD_LIBRARY_PATH=/usr/local/lib release/dataset-skyhook-scan-example file:///mnt/cephfs/nyc