Introduction to Liquibase

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Overview

Liquibase allows you to specify desired database changes using SQL and several other database-independent formats such as XML, YAML, and JSON. Developers can abstract database code to make the propagation of changes to different database types much more accessible.

Before you start, If you don’t have a Liquibase account, create your Liquibase Hub account first.

Download and extract Liquibase

Download Liquibase.

Run the installer or extract the downloaded files.

Open a terminal to view your new directory:

Run the installer or extract the downloaded Liquibase files.

Configure Liquibase

Create a liquibase.properties text file to specify the driver classpath, URL, and user credentials for the database to retrieve.

We can take a look at the properties file of the Postgres Database example below:

changeLogFile:dbchangelog.xml  

url:  jdbc:postgresql://localhost:5432/mydatabase

username:  postgres  

password:  password 

classpath:  postgresql-42.2.8.jar

liquibaseProLicenseKey:  licensekey

liquibase.hub.ApiKey:  APIkey

Take a snapshot of your existing database

Create a usable changelog to capture the current state of the database.

liquibase --changeLogFile=mydatabase_changelog.xml generateChangeLog

Let us take a look at an example:

<?xml version="1.0" encoding="UTF-8"?>  

<databaseChangeLog  

  xmlns="http://www.liquibase.org/xml/ns/dbchangelog"  

  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  

  xmlns:pro="http://www.liquibase.org/xml/ns/pro"  

  xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog 

http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-4.4.xsd

      http://www.liquibase.org/xml/ns/pro 

http://www.liquibase.org/xml/ns/pro/liquibase-pro-4.5.xsd">  

    <changeSet  author="lb-generated"  id="1185214997195-1"> 
 
        <createTable  name="BONUS">  

            <column  name="NAME"  type="VARCHAR2(15)"/>  

            <column  name="JOB"  type="VARCHAR2(255)"/> 
 
            <column  name="SAL"  type="NUMBER(255)"/>

        </createTable>  

    </changeSet>

    <changeSet  author="lb-generated"  id="1185214997195-2">  

        <createTable  name="DEPT">  

            <column  name="DEPTNO"  type="INTEGER"/>  

            <column  name="DNAME"  type="VARCHAR2(15)"/>  

            <column  name="LOC"  type="VARCHAR2(255)"/> 
 
        </createTable>
  
    </changeSet>

    <changeSet  author="lb-generated"  id="1185214997195-3">

         <createView fullDefinition="false" viewName="myView2">SELECT 

"DEPT".DEPTNO,

    "DEPT".DNAME

   FROM "DEPT";</createView>

    </changeSet>

    <changeSet  author="lb-generated"  id="1185214997195-4">
  
        <pro:createFunction functionName="myFunction"

 path="objects/function/myFunction.sql" relativeToChangelogFile="true"/>
  
    </changeSet>

</databaseChangeLog>

Create your first database schema change

You can start modifying the database by creating the first set of changes in the changelog dbchangelog.xml as follows:

<?xml version="1.0" encoding="UTF-8"?>  

<databaseChangeLog 
 
  xmlns="http://www.liquibase.org/xml/ns/dbchangelog"  

  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
 
  xmlns:pro="http://www.liquibase.org/xml/ns/pro" 
 
  xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog 

http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-4.4.xsd

      http://www.liquibase.org/xml/ns/pro 

http://www.liquibase.org/xml/ns/pro/liquibase-pro-4.5.xsd">

    <changeSet author="BobR" id="myIDNumber123">

        <createTable tableName="actor">

            <column autoIncrement="true" name="id" type="INTEGER">

                <constraints nullable="false" primaryKey="true" 

primaryKeyName="actor_pkey"/>

            </column>

            <column name="firstname" type="VARCHAR(255)"/>

            <column name="lastname" type="VARCHAR(255)"/>

            <column name="twitter" type="VARCHAR(15)"/>

        </createTable>

    </changeSet>

</databaseChangeLog>

Register your changelog

liquibase-4.5.0$ liquibase registerChangeLog

Deploy your database change

Now you can deploy your database changes by running the update command as follows:

liquibase-4.5.0$ liquibase update

If all goes well, you will see the following output:

Liquibase: Update has been successful.

You can now automatically undo the last database change by running the rollback command as follows:

liquibase-4.5.0$ liquibase rollbackCount 1

If all goes well, you will see the following output:

Rolling Back Changeset:dbchangelog.xml::myIDNumber123::BobR

Liquibase: Rollback has been successful.

View your project

liquibase-4.5.0$ liquibase registerChangeLog

Set up your dashboard

Create a free account on Liquibase Hub to see database version information about changes occurring in each environment in one place.

When you create an account, you will receive an API key that you can use to connect your changelog to your dashboard. Once connected, you can see in real-time which changes succeeded and which failed in which environments.

Conclusion

In conclusion, in this blog, we have learned about Liquibase installation and setup. I will be covering more topics on Liquibase in my future blogs, stay connected. Happy learning 🙂

For more, you can refer to the Liquibase documentation: https://docs.liquibase.com/home.html

For a more technical blog, you can refer to the Knoldus blog: https://blog.knoldus.com/