[apache#2348] Improvement(docs): Add user doc for relational entity s…

…tore (apache#2768)

### What changes were proposed in this pull request?

Add user documentation for relational entity store. Depends on apache#2584.

### Why are the changes needed?

Fix: apache#2348

---------

Co-authored-by: xiaojiebao <xiaojiebao@xiaomi.com>
Co-authored-by: Jerry Shao <jerryshao@datastrato.com>

docs/how-to-install.md

@@ -43,9 +43,15 @@ The Gravitino binary distribution package contains the following files:
     |   └── log4j2.properties       # log4j configuration for the Gravitino server.
     |── libs/                       # Gravitino server dependencies libraries.
     |── logs/                       # Gravitino server logs. Automatically created after the Gravitino server starts.
-    └── data/                       # Default directory for the Gravitino server to store data.
+    |── data/                       # Default directory for the Gravitino server to store data.
+    └── scripts/                    # Extra scripts for Gravitino.
 ```
 
+#### Initialize the RDBMS (Optional)
+
+If you want to use the relational backend storage, you need to initialize the RDBMS firstly. For
+the details on how to initialize the RDBMS, please check [How to use relational backend storage](./how-to-use-relational-backend-storage.md).
+
 #### Configure the Gravitino server
 
 The Gravitino server configuration file is `conf/gravitino.conf`. You can configure the Gravitino

docs/how-to-use-relational-backend-storage.md

@@ -0,0 +1,90 @@
+---
+title: How to use relational backend storage
+slug: /how-to-use-relational-backend-storage
+license: "Copyright 2024 Datastrato Pvt Ltd.
+This software is licensed under the Apache License version 2."
+---
+
+## Introduction
+
+Before the version `0.5.0`, Gravitino only supports KV backend storage to store metadata. Since
+RDBMS is widely used in the industry, starting from the version `0.5.0`, Gravitino supports using
+RDBMS as relational backend storage to store metadata. This doc will guide you on how to use the
+relational backend storage in Gravitino.
+
+Relational backend storage mainly aims to the users who are accustomed to using RDBMS to
+store data or lack available a KV storage, and want to use Gravitino.
+
+With relational backend storage, you can quickly deploy Gravitino in a production environment and
+take advantage of relational storage to manage metadata.
+
+### What kind of backend storage are supported
+
+Currently, relational backend storage supports the `JDBCBackend`, and uses `MySQL` as the
+default storage for `JDBCBackend`.
+
+## How to use
+
+### Prerequisites
+
++ MySQL 5.7 or 8.0.
++ Gravitino distribution package.
++ MySQL connector Jar (Should be compatible with the version of MySQL instance).
+
+### Step 1: Get the initialization script
+
+You need to `download` and `unzip` the distribution package firstly, please see
+[How to install Gravitino](how-to-install.md).
+
+Then you can get the initialization script in the directory:
+
+```text
+${GRAVITINO_HOME}/scripts/mysql/
+```
+
+The script name is like `schema-{version}-mysql.sql`, and the `version` depends on your Gravitino version.
+For example, if your Gravitino version is `0.6.0`, then you can choose the **latest version** script
+file that is equal or smaller than `0.6.0`, you can choose the `schema-0.5.0-mysql.sql` script.
+
+### Step 2: Initialize the database
+
+Please create a database in MySQL in advance, and execute the initialization script obtained above in the database.
+
+### Step 3: Place the MySQL connector Jar
+
+You should **download** the MySQL connector Jar for the corresponding version of MySQL you use
+(You can download it from the [maven-central-repo](https://repo1.maven.org/maven2/mysql/mysql-connector-java/)),
+which is name like `mysql-connector-java-{version}.jar`.
+
+Then please place it in the distribution package directory:
+
+```text
+${GRAVITINO_HOME}/libs/
+```
+
+### Step 4: Set up the Gravitino server configs
+
+Find the server configuration file which name is `gravitino.conf` in the distribution package directory:
+
+```text
+${GRAVITINO_HOME}/conf/
+```
+
+Then set up the following server configs:
+
+```text
+gravitino.entity.store = relational
+gravitino.entity.store.relational = JDBCBackend
+gravitino.entity.store.relational.jdbcUrl = ${your_jdbc_url}
+gravitino.entity.store.relational.jdbcDriver = ${your_driver_name}
+gravitino.entity.store.relational.jdbcUser = ${your_username}
+gravitino.entity.store.relational.jdbcPassword = ${your_password}
+```
+
+### Step 5: Start the server
+
+Finally, you can run the script in the distribution package directory to start the server:
+
+```shell
+./${GRAVITINO_HOME}/bin/gravitino.sh start
+```