Update an existing trigger into Liquibase - sql

Question

I'm very new at Liquibase, and I need some help.
I have an existing trigger that was not capturing all the data; I made some changes to my local Oracle database. Now I need to add those changes into the Liquibase, but I'm lost how to do that.
I know you cannot breach the contract in liquibase by updating the original .xml file directly.
From my understanding, I need to create a new changelog .XML file and then include the path on the other post_migration file.
My confusion is, do I have to drop the original trigger, then create a new file or?
Thanks!

Answer 1

I never create triggers, procedures or even views within the XML file exactly because this makes things more complicated (I think).
I typically move the actual trigger definition into a SQL script (that I can also run separately during development and testing), then include that SQL file from within the Liquibase changelog:
<changeSet id="42" author="arthur" runOnChange="true">
<sqlFile path="triggers/some_trigger.sql"
stripComments="false"
splitStatements="true"
endDelimiter="/"
relativeToChangelogFile="true"/>
</changeSet>
The some_trigger.sql script is stored in git (svn, ...) together with the XML changelog. The runOnChange="true" is the "magical ingredient" here. You don't have to touch the XML file, you just edit the SQL script. During deployment, Liquibase will check if the (SQL) file has changed and run the script if needec.

Answer 2

So, I believe that you create/update/replace the SQL trigger in your local developer database and right now you want to include the liquibase script to the release distribution package of your product.
The liquibase doesn't provide special xml syntax to create triggers, so you will just add a new changeset that holds your pl/sql script inside the <SQL> tag. The script will be the same that you run on your local database.
The example code here:
<changeSet id="1" author="me">
<sql endDelimiter="/">
CREATE OR REPLACE TRIGGER trigger_name before insert
on table1_name for each row
BEGIN
select seq_myseq.nextval
into :new.myid
from dual;
END;
/
</sql>
</changeSet>
This code just compile trigger in the aimed database when you call liquibase update. In most cases, it is enough. But I strictly recommend you to ask your DBA or team led for rules that your team enforced for writing liquibase scripts. For this reason, the result may be much more complicated.