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`TiDB`_
==========

TiDB is an open-source NewSQL database that supports Hybrid Transactional and Analytical Processing
(HTAP) workloads.

TiSpark is a thin layer built for running Apache Spark on top of TiDB/TiKV to answer complex OLAP
queries. It enjoys the merits of both the Spark platform and the distributed clusters
of TiKV while seamlessly integrated to TiDB to provide one-stop HTAP solutions for online
transactions and analyses.

.. tip::
   This article assumes that you have mastered the basic knowledge and operation of TiDB and TiSpark.
   For the knowledge not mentioned in this article, you can obtain it from TiDB `Official Documentation`_.

By using kyuubi, we can run SQL queries towards TiDB/TiKV which is more
convenient, easy to understand, and easy to expand than directly using
spark to manipulate TiDB/TiKV.

TiDB Integration
-------------------

To enable the integration of Kyuubi Spark SQL engine and TiDB through
Spark DataSource V2 API, you need to:

- Referencing the TiSpark :ref:`dependencies<spark-tidb-deps>`
- Setting the Spark extension and catalog :ref:`configurations<spark-tidb-conf>`

.. _spark-tidb-deps:

Dependencies
************
The classpath of Kyuubi Spark SQL engine with TiDB supported consists of

1. kyuubi-spark-sql-engine-\ |release|\ _2.12.jar, the engine jar deployed with a Kyuubi distribution
2. a copy of Spark distribution
3. tispark-assembly-<spark.version>_<scala.version>-<tispark.version>.jar (example: tispark-assembly-3.2_2.12-3.0.1.jar), which can be found in the `Maven Central`_

In order to make the TiSpark packages visible for the runtime classpath of engines, we can use one of these methods:

1. Put the TiSpark packages into ``$SPARK_HOME/jars`` directly
2. Set ``spark.jars=/path/to/tispark-assembly``

.. warning::
   Please mind the compatibility of different TiDB, TiSpark and Spark versions, which can be confirmed on the page of `TiSpark Environment setup`_.

.. _spark-tidb-conf:

Configurations
**************

To activate functionality of TiSpark, we can set the following configurations:

.. code-block:: properties

   spark.tispark.pd.addresses $pd_host:$pd_port
   spark.sql.extensions org.apache.spark.sql.TiExtensions
   spark.sql.catalog.tidb_catalog  org.apache.spark.sql.catalyst.catalog.TiCatalog
   spark.sql.catalog.tidb_catalog.pd.addresses $pd_host:$pd_port

The `spark.tispark.pd.addresses` and `spark.sql.catalog.tidb_catalog.pd.addresses` configurations
allow you to put in multiple PD servers. Specify the port number for each of them.

For example, when you have multiple PD servers on `10.16.20.1,10.16.20.2,10.16.20.3` with the port `2379`,
put it as `10.16.20.1:2379,10.16.20.2:2379,10.16.20.3:2379`.

TiDB Operations
------------------

Taking ``SELECT`` as a example,

.. code-block:: sql

   SELECT * FROM foo;

Taking ``DELETE FROM`` as a example, Spark 3 added support for DELETE FROM queries to remove data from tables.

.. code-block:: sql

   DELETE FROM foo WHERE id >= 1 and id < 2;

.. note::
   As for now (TiSpark 3.0.1), TiSpark does not support ``CREATE TABLE``, ``INSERT INTO/OVERWRITE`` operations
   through Apache Spark Datasource V2 and Catalog APIs.

.. _Official Documentation: https://docs.pingcap.com/tidb/stable/overview
.. _Maven Central: https://repo1.maven.org/maven2/com/pingcap/tispark/
.. _TiSpark Environment setup: https://docs.pingcap.com/tidb/stable/tispark-overview#environment-setup